position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
Component that wraps platform ScrollView while providing integration with touch locking "responder" system.
-
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes easy to debug.
+
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector can be used to debug.
Doesn't yet support other contained responders from blocking this scroll view from becoming the responder.
-
<ScrollView> vs <ListView> - which one to use? ScrollView simply renders all its react child components at once. That makes it very easy to understand and use. On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, worth of couple of your ScrollView’s heights. Creating JS components and native views upfront for all its items, which may not even be shown, will contribute to slow rendering of your screen and increased memory usage.
-
This is where ListView comes into play. ListView renders items lazily, just when they are about to appear. This laziness comes at cost of a more complicated API, which is worth it unless you are rendering a small fixed set of items.
+
<ScrollView> vs <ListView> - which one to use? ScrollView renders all its react child components at once. That makes it very understandable and useful. On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, worth of couple of your ScrollView’s heights. Creating JS components and native views upfront for all its items, which may not even be shown, will contribute to slow rendering of your screen and increased memory usage.
+
This is where ListView comes into play. ListView renders items lazily, right when they are about to appear. This laziness comes at cost of a more complicated API, which is worth it unless you are rendering a small fixed set of items.
black, scroll indicator is black. This style is good against a white content background.
-
white, scroll indicator is white. This style is good against a black content background.
+
default (the default), same as black.
+
+- `black`, scroll indicator is black. This style is good against a light content background.
+
+- `white`, scroll indicator is white. This style is good against a dark content background.
+
Component that wraps platform ScrollView while providing integration with touch locking "responder" system.
-
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes easy to debug.
+
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector can be used to debug.
Doesn't yet support other contained responders from blocking this scroll view from becoming the responder.
-
<ScrollView> vs <ListView> - which one to use? ScrollView simply renders all its react child components at once. That makes it very easy to understand and use. On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, worth of couple of your ScrollView’s heights. Creating JS components and native views upfront for all its items, which may not even be shown, will contribute to slow rendering of your screen and increased memory usage.
-
This is where ListView comes into play. ListView renders items lazily, just when they are about to appear. This laziness comes at cost of a more complicated API, which is worth it unless you are rendering a small fixed set of items.
+
<ScrollView> vs <ListView> - which one to use? ScrollView renders all its react child components at once. That makes it very understandable and useful. On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, worth of couple of your ScrollView’s heights. Creating JS components and native views upfront for all its items, which may not even be shown, will contribute to slow rendering of your screen and increased memory usage.
+
This is where ListView comes into play. ListView renders items lazily, right when they are about to appear. This laziness comes at cost of a more complicated API, which is worth it unless you are rendering a small fixed set of items.
black, scroll indicator is black. This style is good against a white content background.
-
white, scroll indicator is white. This style is good against a black content background.
+
default (the default), same as black.
+
+- `black`, scroll indicator is black. This style is good against a light content background.
+
+- `white`, scroll indicator is white. This style is good against a dark content background.
+
A foundational component for inputting text into the app via a keyboard. Props provide configurability for several features, such as auto-correction, auto-capitalization, placeholder text, and different keyboard types, such as a numeric keypad.
-
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A simple example:
+
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. An example:
Provides an initial value that will change when the user starts typing. Useful for simple use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
+
Provides an initial value that will change when the user starts typing. Useful for use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to simply setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
+
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
A foundational component for inputting text into the app via a keyboard. Props provide configurability for several features, such as auto-correction, auto-capitalization, placeholder text, and different keyboard types, such as a numeric keypad.
-
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A simple example:
+
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. An example:
Provides an initial value that will change when the user starts typing. Useful for simple use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
+
Provides an initial value that will change when the user starts typing. Useful for use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to simply setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
+
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
The Animated library is designed to make animations fluid, powerful, and easy to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and simple start/stop methods to control time-based animation execution.
-
The simplest workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
The Animated library is designed to make animations fluid, powerful, and painless to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and start/stop methods to control time-based animation execution.
+
The most basic workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
Animated.timing(// Animate value over timethis.state.fadeAnim,// The value to drive
@@ -90,7 +90,7 @@
Animated provides three types of animation types. Each animation type provides a particular animation curve that controls how your values animate from their initial value to the final value:
Animated.decay() starts with an initial velocity and gradually slows to a stop.
In most cases, you will be using timing(). By default, it uses a symmetric easeInOut curve that conveys the gradual acceleration of an object to full speed and concludes by gradually decelerating to a stop.
@@ -100,7 +100,7 @@
By using the native driver, we send everything about the animation to native before starting the animation, allowing native code to perform the animation on the UI thread without having to go through the bridge on every frame. Once the animation has started, the JS thread can be blocked without affecting the animation.
You can use the native driver by specifying useNativeDriver: true in your animation configuration. See the Animations guide to learn more.
Animatable components
-
Only animatable components can be animated. These special components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
+
Only animatable components can be animated. These unique components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
Animated.sequence() starts the animations in order, waiting for each to complete before starting the next.
Animated.stagger() starts animations in order and in parallel, but with successive delays.
-
Animations can also be chained together simply by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
+
Animations can also be chained together by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
By default, if one animation is stopped or interrupted, then all other animations in the group are also stopped.
Combining animated values
You can combine two animated values via addition, subtraction, multiplication, division, or modulo to make a new animated value:
@@ -189,14 +189,14 @@
Animates a value according to an analytical spring model based on damped harmonic oscillation. Tracks velocity state to create fluid motions as the toValue updates, and can be chained together.
Config is an object that may have the following options.
Note that you can only define one of bounciness/speed, tension/friction, or stiffness/damping/mass, but not more than one:
-
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
+
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
speed: Controls speed of the animation. Default 12.
bounciness: Controls bounciness. Default 8.
-
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation primitive.
+
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation.
stiffness: The spring stiffness coefficient. Default 100.
damping: Defines how the spring’s motion should be damped due to the forces of friction. Default 10.
@@ -297,7 +297,7 @@
forkEvent()
staticforkEvent(event, listener)
-
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a simple javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
+
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
The Animated library is designed to make animations fluid, powerful, and easy to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and simple start/stop methods to control time-based animation execution.
-
The simplest workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
The Animated library is designed to make animations fluid, powerful, and painless to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and start/stop methods to control time-based animation execution.
+
The most basic workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
Animated.timing(// Animate value over timethis.state.fadeAnim,// The value to drive
@@ -90,7 +90,7 @@
Animated provides three types of animation types. Each animation type provides a particular animation curve that controls how your values animate from their initial value to the final value:
Animated.decay() starts with an initial velocity and gradually slows to a stop.
In most cases, you will be using timing(). By default, it uses a symmetric easeInOut curve that conveys the gradual acceleration of an object to full speed and concludes by gradually decelerating to a stop.
@@ -100,7 +100,7 @@
By using the native driver, we send everything about the animation to native before starting the animation, allowing native code to perform the animation on the UI thread without having to go through the bridge on every frame. Once the animation has started, the JS thread can be blocked without affecting the animation.
You can use the native driver by specifying useNativeDriver: true in your animation configuration. See the Animations guide to learn more.
Animatable components
-
Only animatable components can be animated. These special components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
+
Only animatable components can be animated. These unique components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
Animated.sequence() starts the animations in order, waiting for each to complete before starting the next.
Animated.stagger() starts animations in order and in parallel, but with successive delays.
-
Animations can also be chained together simply by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
+
Animations can also be chained together by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
By default, if one animation is stopped or interrupted, then all other animations in the group are also stopped.
Combining animated values
You can combine two animated values via addition, subtraction, multiplication, division, or modulo to make a new animated value:
@@ -189,14 +189,14 @@
Animates a value according to an analytical spring model based on damped harmonic oscillation. Tracks velocity state to create fluid motions as the toValue updates, and can be chained together.
Config is an object that may have the following options.
Note that you can only define one of bounciness/speed, tension/friction, or stiffness/damping/mass, but not more than one:
-
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
+
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
speed: Controls speed of the animation. Default 12.
bounciness: Controls bounciness. Default 8.
-
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation primitive.
+
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation.
stiffness: The spring stiffness coefficient. Default 100.
damping: Defines how the spring’s motion should be damped due to the forces of friction. Default 10.
@@ -297,7 +297,7 @@
forkEvent()
staticforkEvent(event, listener)
-
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a simple javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
+
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
Add a handler to AppState changes by listening to the change event type and providing the handler
-
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and just use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
+
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
Add a handler to AppState changes by listening to the change event type and providing the handler
-
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and just use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
+
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
AsyncStorage is a simple, unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
+
AsyncStorage is an unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.
On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. On Android, AsyncStorage will use either RocksDB or SQLite based on what is available.
-
The AsyncStorage JavaScript code is a simple facade that provides a clear JavaScript API, real Error objects, and simple non-multi functions. Each method in the API returns a Promise object.
+
The AsyncStorage JavaScript code is a facade that provides a clear JavaScript API, real Error objects, and non-multi functions. Each method in the API returns a Promise object.
AsyncStorage is a simple, unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
+
AsyncStorage is an unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.
On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. On Android, AsyncStorage will use either RocksDB or SQLite based on what is available.
-
The AsyncStorage JavaScript code is a simple facade that provides a clear JavaScript API, real Error objects, and simple non-multi functions. Each method in the API returns a Promise object.
+
The AsyncStorage JavaScript code is a facade that provides a clear JavaScript API, real Error objects, and non-multi functions. Each method in the API returns a Promise object.
In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.
Introduction
React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and its own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If an ancestor component relies on the state of its descendant, one should pass down a callback to be used by the descendant to update the ancestor.
-
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.
+
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some specific, cross-language mechanisms that would allow us to pass information between them.
Properties
Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.
Passing properties from native to React Native
@@ -66,7 +66,7 @@ mReactRootView.Passing properties from React Native to native
-
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then just use them in React Native as if the component was an ordinary React Native component.
+
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then use them in React Native as if the component was an ordinary React Native component.
Limits of properties
The main drawback of cross-language properties is that they do not support callbacks, which would allow us to handle bottom-up data bindings. Imagine you have a small RN view that you want to be removed from the native parent view as a result of a JS action. There is no way to do that with props, as the information would need to go bottom-up.
Although we have a flavor of cross-language callbacks (described here), these callbacks are not always the thing we need. The main problem is that they are not intended to be passed as properties. Rather, this mechanism allows us to trigger a native action from JS, and handle the result of that action in JS.
In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.
Introduction
React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and its own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If an ancestor component relies on the state of its descendant, one should pass down a callback to be used by the descendant to update the ancestor.
-
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.
+
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some specific, cross-language mechanisms that would allow us to pass information between them.
Properties
Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.
Passing properties from native to React Native
@@ -66,7 +66,7 @@ mReactRootView.Passing properties from React Native to native
-
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then just use them in React Native as if the component was an ordinary React Native component.
+
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then use them in React Native as if the component was an ordinary React Native component.
Limits of properties
The main drawback of cross-language properties is that they do not support callbacks, which would allow us to handle bottom-up data bindings. Imagine you have a small RN view that you want to be removed from the native parent view as a result of a JS action. There is no way to do that with props, as the information would need to go bottom-up.
Although we have a flavor of cross-language callbacks (described here), these callbacks are not always the thing we need. The main problem is that they are not intended to be passed as properties. Rather, this mechanism allows us to trigger a native action from JS, and handle the result of that action in JS.
Provides an initial value that will change when the user starts selecting a date. It is useful for simple use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
+
Provides an initial value that will change when the user starts selecting a date. It is useful for use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
Provides an initial value that will change when the user starts selecting a date. It is useful for simple use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
+
Provides an initial value that will change when the user starts selecting a date. It is useful for use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is both efficient and easy to use if you have fixed size items, for example:
+
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is efficient if you have fixed size items, for example:
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is both efficient and easy to use if you have fixed size items, for example:
+
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is efficient if you have fixed size items, for example:
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, simply enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
+
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
First, ensure you're using at least version 0.60.4 of React Native.
If you have an existing app based on an earlier version of React Native, you will have to upgrade it first. See Upgrading to new React Native Versions for how to do this. Make especially sure that all changes to android/app/build.gradle have been applied, as detailed by the React Native upgrade helper. After upgrading the app, make sure everything works before trying to switch to Hermes.
@@ -95,7 +95,7 @@
$ react-native run-android
Confirming Hermes is in use
-
If you've just created a new app from scratch you should see if Hermes is enabled in the welcome view:
+
If you've recently created a new app from scratch you should see if Hermes is enabled in the welcome view:
A HermesInternal global variable will be available in JavaScript that can be used to verify that Hermes is in use:
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, simply enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
+
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
First, ensure you're using at least version 0.60.4 of React Native.
If you have an existing app based on an earlier version of React Native, you will have to upgrade it first. See Upgrading to new React Native Versions for how to do this. Make especially sure that all changes to android/app/build.gradle have been applied, as detailed by the React Native upgrade helper. After upgrading the app, make sure everything works before trying to switch to Hermes.
@@ -95,7 +95,7 @@
$ react-native run-android
Confirming Hermes is in use
-
If you've just created a new app from scratch you should see if Hermes is enabled in the welcome view:
+
If you've recently created a new app from scratch you should see if Hermes is enabled in the welcome view:
A HermesInternal global variable will be available in JavaScript that can be used to verify that Hermes is in use:
A common feature request from developers familiar with the web is background-image. To handle this use case, you can use the <ImageBackground> component, which has the same props as <Image>, and add whatever children to it you would like to layer on top of it.
-
You might not want to use <ImageBackground> in some cases, since the implementation is very simple. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
+
You might not want to use <ImageBackground> in some cases, since the implementation is basic. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
Note that you must specify some width and height style attributes.
A common feature request from developers familiar with the web is background-image. To handle this use case, you can use the <ImageBackground> component, which has the same props as <Image>, and add whatever children to it you would like to layer on top of it.
-
You might not want to use <ImageBackground> in some cases, since the implementation is very simple. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
+
You might not want to use <ImageBackground> in some cases, since the implementation is basic. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
Note that you must specify some width and height style attributes.
A component which enables customization of the keyboard input accessory view on iOS. The input accessory view is displayed above the keyboard whenever a TextInput has focus. This component can be used to create custom toolbars.
-
To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A simple example:
+
To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A basic example:
A component which enables customization of the keyboard input accessory view on iOS. The input accessory view is displayed above the keyboard whenever a TextInput has focus. This component can be used to create custom toolbars.
-
To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A simple example:
+
To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A basic example:
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
React Native is not only for Android and iOS - there are community-supported projects that bring it to other platforms, such as:
React Native Windows - React Native support for Microsoft's Universal Windows Platform (UWP) and the Windows Presentation Foundation (WPF)
React Native DOM - An experimental, comprehensive port of React Native to the web. (Not to be confused with React Native Web, which has different goals)
React Native is not only for Android and iOS - there are community-supported projects that bring it to other platforms, such as:
React Native Windows - React Native support for Microsoft's Universal Windows Platform (UWP) and the Windows Presentation Foundation (WPF)
React Native DOM - An experimental, comprehensive port of React Native to the web. (Not to be confused with React Native Web, which has different goals)
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize basic multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state, by replacing the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize basic multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
+
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state, by replacing the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
The purpose of SafeAreaView is to render content within the safe area boundaries of a device. It is currently only applicable to iOS devices with iOS version 11 or later.
-
SafeAreaView renders nested content and automatically applies paddings to reflect the portion of the view that is not covered by navigation bars, tab bars, toolbars, and other ancestor views. Moreover, and most importantly, Safe Area's paddings reflect the physical limitation of the screen, such as rounded corners or camera notches (i.e. the sensor housing area on iPhone X).
+
SafeAreaView renders nested content and automatically applies padding to reflect the portion of the view that is not covered by navigation bars, tab bars, toolbars, and other ancestor views. Moreover, and most importantly, Safe Area's paddings reflect the physical limitation of the screen, such as rounded corners or camera notches (i.e. the sensor housing area on iPhone X).
Usage Example
-
Simply wrap your top level view with a SafeAreaView with a flex: 1 style applied to it. You may also want to use a background color that matches your application's design.
+
To use, wrap your top level view with a SafeAreaView with a flex: 1 style applied to it. You may also want to use a background color that matches your application's design.
The purpose of SafeAreaView is to render content within the safe area boundaries of a device. It is currently only applicable to iOS devices with iOS version 11 or later.
-
SafeAreaView renders nested content and automatically applies paddings to reflect the portion of the view that is not covered by navigation bars, tab bars, toolbars, and other ancestor views. Moreover, and most importantly, Safe Area's paddings reflect the physical limitation of the screen, such as rounded corners or camera notches (i.e. the sensor housing area on iPhone X).
+
SafeAreaView renders nested content and automatically applies padding to reflect the portion of the view that is not covered by navigation bars, tab bars, toolbars, and other ancestor views. Moreover, and most importantly, Safe Area's paddings reflect the physical limitation of the screen, such as rounded corners or camera notches (i.e. the sensor housing area on iPhone X).
Usage Example
-
Simply wrap your top level view with a SafeAreaView with a flex: 1 style applied to it. You may also want to use a background color that matches your application's design.
+
To use, wrap your top level view with a SafeAreaView with a flex: 1 style applied to it. You may also want to use a background color that matches your application's design.
Component that wraps platform ScrollView while providing integration with touch locking "responder" system.
-
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes easy to debug.
+
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes quick to debug.
Doesn't yet support other contained responders from blocking this scroll view from becoming the responder.
ScrollView simply renders all its react child components at once. That makes it very easy to understand and use.
-
On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, maybe several screens worth of content. Creating JS components and native views for everything all at once, much of which may not even be shown, will contribute to slow rendering and increased memory usage.
-
This is where FlatList comes into play. FlatList renders items lazily, just when they are about to appear, and removes items that scroll way off screen to save memory and processing time.
+
ScrollView renders all its react child components at once, but this has a performance downside.
+
Imagine you have a very long list of items you want to display, maybe several screens worth of content. Creating JS components and native views for everything all at once, much of which may not even be shown, will contribute to slow rendering and increased memory usage.
+
This is where FlatList comes into play. FlatList renders items lazily, when they are about to appear, and removes items that scroll way off screen to save memory and processing time.
FlatList is also handy if you want to render separators between your items, multiple columns, infinite scroll loading, or any number of other features it supports out of the box.
When set, the scroll view will adjust the scroll position so that the first child that is currently visible and at or beyond minIndexForVisible will not change position. This is useful for lists that are loading content in both directions, e.g. a chat thread, where new messages coming in might otherwise cause the scroll position to jump. A value of 0 is common, but other values such as 1 can be used to skip loading spinners or other content that should not maintain position.
The optional autoscrollToTopThreshold can be used to make the content automatically scroll to the top after making the adjustment if the user was within the threshold of the top before the adjustment was made. This is also useful for chat-like applications where you want to see new messages scroll into place, but not if the user has scrolled up a ways and it would be disruptive to scroll a bunch.
Caveat 1: Reordering elements in the scrollview with this enabled will probably cause jumpiness and jank. It can be fixed, but there are currently no plans to do so. For now, don't re-order the content of any ScrollViews or Lists that use this feature.
-
Caveat 2: This simply uses contentOffset and frame.origin in native code to compute visibility. Occlusion, transforms, and other complexity won't be taken into account as to whether content is "visible" or not.
+
Caveat 2: This uses contentOffset and frame.origin in native code to compute visibility. Occlusion, transforms, and other complexity won't be taken into account as to whether content is "visible" or not.
Component that wraps platform ScrollView while providing integration with touch locking "responder" system.
-
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes easy to debug.
+
Keep in mind that ScrollViews must have a bounded height in order to work, since they contain unbounded-height children into a bounded container (via a scroll interaction). In order to bound the height of a ScrollView, either set the height of the view directly (discouraged) or make sure all parent views have bounded height. Forgetting to transfer {flex: 1} down the view stack can lead to errors here, which the element inspector makes quick to debug.
Doesn't yet support other contained responders from blocking this scroll view from becoming the responder.
ScrollView simply renders all its react child components at once. That makes it very easy to understand and use.
-
On the other hand, this has a performance downside. Imagine you have a very long list of items you want to display, maybe several screens worth of content. Creating JS components and native views for everything all at once, much of which may not even be shown, will contribute to slow rendering and increased memory usage.
-
This is where FlatList comes into play. FlatList renders items lazily, just when they are about to appear, and removes items that scroll way off screen to save memory and processing time.
+
ScrollView renders all its react child components at once, but this has a performance downside.
+
Imagine you have a very long list of items you want to display, maybe several screens worth of content. Creating JS components and native views for everything all at once, much of which may not even be shown, will contribute to slow rendering and increased memory usage.
+
This is where FlatList comes into play. FlatList renders items lazily, when they are about to appear, and removes items that scroll way off screen to save memory and processing time.
FlatList is also handy if you want to render separators between your items, multiple columns, infinite scroll loading, or any number of other features it supports out of the box.
When set, the scroll view will adjust the scroll position so that the first child that is currently visible and at or beyond minIndexForVisible will not change position. This is useful for lists that are loading content in both directions, e.g. a chat thread, where new messages coming in might otherwise cause the scroll position to jump. A value of 0 is common, but other values such as 1 can be used to skip loading spinners or other content that should not maintain position.
The optional autoscrollToTopThreshold can be used to make the content automatically scroll to the top after making the adjustment if the user was within the threshold of the top before the adjustment was made. This is also useful for chat-like applications where you want to see new messages scroll into place, but not if the user has scrolled up a ways and it would be disruptive to scroll a bunch.
Caveat 1: Reordering elements in the scrollview with this enabled will probably cause jumpiness and jank. It can be fixed, but there are currently no plans to do so. For now, don't re-order the content of any ScrollViews or Lists that use this feature.
-
Caveat 2: This simply uses contentOffset and frame.origin in native code to compute visibility. Occlusion, transforms, and other complexity won't be taken into account as to whether content is "visible" or not.
+
Caveat 2: This uses contentOffset and frame.origin in native code to compute visibility. Occlusion, transforms, and other complexity won't be taken into account as to whether content is "visible" or not.
Get and remove the last a StatusBar entry from the stack.
Parameters:
diff --git a/docs/0.60/text.html b/docs/0.60/text.html
index cbcd336e7e1..c2ec19841cd 100644
--- a/docs/0.60/text.html
+++ b/docs/0.60/text.html
@@ -157,7 +157,7 @@
9-17: bold, red
Containers
-
The <Text> element is special relative to layout: everything inside is no longer using the flexbox layout but using text layout. This means that elements inside of a <Text> are no longer rectangles, but wrap when they see the end of the line.
+
The <Text> element is unique relative to layout: everything inside is no longer using the flexbox layout but using text layout. This means that elements inside of a <Text> are no longer rectangles, but wrap when they see the end of the line.
<Text><Text>First part and </Text><Text>second part</Text>
@@ -213,7 +213,7 @@
<MyAppHeaderText>Text styled as a header</MyAppHeaderText></View>
-
Assuming that MyAppText is a component that simply renders out its children into a Text component with styling, then MyAppHeaderText can be defined as follows:
+
Assuming that MyAppText is a component that only renders out its children into a Text component with styling, then MyAppHeaderText can be defined as follows:
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
Type
Required
diff --git a/docs/0.60/text/index.html b/docs/0.60/text/index.html
index cbcd336e7e1..c2ec19841cd 100644
--- a/docs/0.60/text/index.html
+++ b/docs/0.60/text/index.html
@@ -157,7 +157,7 @@
9-17: bold, red
Containers
-
The <Text> element is special relative to layout: everything inside is no longer using the flexbox layout but using text layout. This means that elements inside of a <Text> are no longer rectangles, but wrap when they see the end of the line.
+
The <Text> element is unique relative to layout: everything inside is no longer using the flexbox layout but using text layout. This means that elements inside of a <Text> are no longer rectangles, but wrap when they see the end of the line.
<Text><Text>First part and </Text><Text>second part</Text>
@@ -213,7 +213,7 @@
<MyAppHeaderText>Text styled as a header</MyAppHeaderText></View>
-
Assuming that MyAppText is a component that simply renders out its children into a Text component with styling, then MyAppHeaderText can be defined as follows:
+
Assuming that MyAppText is a component that only renders out its children into a Text component with styling, then MyAppHeaderText can be defined as follows:
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
A foundational component for inputting text into the app via a keyboard. Props provide configurability for several features, such as auto-correction, auto-capitalization, placeholder text, and different keyboard types, such as a numeric keypad.
-
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A simple example:
+
The most basic use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A minimal example:
Provides an initial value that will change when the user starts typing. Useful for simple use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
+
Provides an initial value that will change when the user starts typing. Useful for use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
Type
Required
@@ -892,7 +892,7 @@ export default function UselessTextInputMultiline() {
value
-
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to simply setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
+
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
A foundational component for inputting text into the app via a keyboard. Props provide configurability for several features, such as auto-correction, auto-capitalization, placeholder text, and different keyboard types, such as a numeric keypad.
-
The simplest use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A simple example:
+
The most basic use case is to plop down a TextInput and subscribe to the onChangeText events to read the user input. There are also other events, such as onSubmitEditing and onFocus that can be subscribed to. A minimal example:
Provides an initial value that will change when the user starts typing. Useful for simple use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
+
Provides an initial value that will change when the user starts typing. Useful for use-cases where you do not want to deal with listening to events and updating the value prop to keep the controlled state in sync.
Type
Required
@@ -892,7 +892,7 @@ export default function UselessTextInputMultiline() {
value
-
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to simply setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
+
The value to show for the text input. TextInput is a controlled component, which means the native value will be forced to match this value prop if provided. For most uses, this works great, but in some cases this may cause flickering - one common cause is preventing edits by keeping value the same. In addition to setting the same value, either set editable={false}, or set/update maxLength to prevent unwanted edits without flicker.
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
There will be no effect on devices that do not support Vibration, eg. the simulator.
Note for Android: add <uses-permission android:name="android.permission.VIBRATE"/> to AndroidManifest.xml
The vibration duration in iOS is not configurable, so there are some differences with Android. In Android, if pattern is a number, it specifies the vibration duration in ms. If pattern is an array, those odd indices are the vibration duration, while the even ones are the separation time.
-
In iOS, invoking vibrate(duration) will just ignore the duration and vibrate for a fixed time. While the pattern array is used to define the duration between each vibration. See below example for more.
+
In iOS, invoking vibrate(duration) will ignore the duration and vibrate for a fixed time. While the pattern array is used to define the duration between each vibration. See below example for more.
Repeatable vibration is also supported, the vibration will repeat with defined pattern until cancel() is called.
There will be no effect on devices that do not support Vibration, eg. the simulator.
Note for Android: add <uses-permission android:name="android.permission.VIBRATE"/> to AndroidManifest.xml
The vibration duration in iOS is not configurable, so there are some differences with Android. In Android, if pattern is a number, it specifies the vibration duration in ms. If pattern is an array, those odd indices are the vibration duration, while the even ones are the separation time.
-
In iOS, invoking vibrate(duration) will just ignore the duration and vibrate for a fixed time. While the pattern array is used to define the duration between each vibration. See below example for more.
+
In iOS, invoking vibrate(duration) will ignore the duration and vibrate for a fixed time. While the pattern array is used to define the duration between each vibration. See below example for more.
Repeatable vibration is also supported, the vibration will repeat with defined pattern until cancel() is called.
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
Type
Required
@@ -375,7 +375,7 @@
removeClippedSubviews
-
This is a special performance property exposed by RCTView and is useful for scrolling content when there are many subviews, most of which are offscreen. For this property to be effective, it must be applied to a view that contains many subviews that extend outside its bound. The subviews must also have overflow: hidden, as should the containing view (or one of its superviews).
+
This is a reserved performance property exposed by RCTView and is useful for scrolling content when there are many subviews, most of which are offscreen. For this property to be effective, it must be applied to a view that contains many subviews that extend outside its bound. The subviews must also have overflow: hidden, as should the containing view (or one of its superviews).
Type
Required
@@ -470,7 +470,7 @@
renderToHardwareTextureAndroid
Whether this View should render itself (and all of its children) into a single hardware texture on the GPU.
-
On Android, this is useful for animations and interactions that only modify opacity, rotation, translation, and/or scale: in those cases, the view doesn't have to be redrawn and display lists don't need to be re-executed. The texture can just be re-used and re-composited with different parameters. The downside is that this can use up limited video memory, so this prop should be set back to false at the end of the interaction/animation.
+
On Android, this is useful for animations and interactions that only modify opacity, rotation, translation, and/or scale: in those cases, the view doesn't have to be redrawn and display lists don't need to be re-executed. The texture can be re-used and re-composited with different parameters. The downside is that this can use up limited video memory, so this prop should be set back to false at the end of the interaction/animation.
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not obvious from the accessibility label.
+
An accessibility hint helps users understand what will happen when they perform an action on the accessibility element when that result is not clear from the accessibility label.
Type
Required
@@ -375,7 +375,7 @@
removeClippedSubviews
-
This is a special performance property exposed by RCTView and is useful for scrolling content when there are many subviews, most of which are offscreen. For this property to be effective, it must be applied to a view that contains many subviews that extend outside its bound. The subviews must also have overflow: hidden, as should the containing view (or one of its superviews).
+
This is a reserved performance property exposed by RCTView and is useful for scrolling content when there are many subviews, most of which are offscreen. For this property to be effective, it must be applied to a view that contains many subviews that extend outside its bound. The subviews must also have overflow: hidden, as should the containing view (or one of its superviews).
Type
Required
@@ -470,7 +470,7 @@
renderToHardwareTextureAndroid
Whether this View should render itself (and all of its children) into a single hardware texture on the GPU.
-
On Android, this is useful for animations and interactions that only modify opacity, rotation, translation, and/or scale: in those cases, the view doesn't have to be redrawn and display lists don't need to be re-executed. The texture can just be re-used and re-composited with different parameters. The downside is that this can use up limited video memory, so this prop should be set back to false at the end of the interaction/animation.
+
On Android, this is useful for animations and interactions that only modify opacity, rotation, translation, and/or scale: in those cases, the view doesn't have to be redrawn and display lists don't need to be re-executed. The texture can be re-used and re-composited with different parameters. The downside is that this can use up limited video memory, so this prop should be set back to false at the end of the interaction/animation.
The Animated library is designed to make animations fluid, powerful, and easy to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and simple start/stop methods to control time-based animation execution.
-
The simplest workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
The Animated library is designed to make animations fluid, powerful, and painless to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and start/stop methods to control time-based animation execution.
+
The most basic workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
Animated.timing(// Animate value over timethis.state.fadeAnim,// The value to drive
@@ -90,7 +90,7 @@
Animated provides three types of animation types. Each animation type provides a particular animation curve that controls how your values animate from their initial value to the final value:
Animated.decay() starts with an initial velocity and gradually slows to a stop.
In most cases, you will be using timing(). By default, it uses a symmetric easeInOut curve that conveys the gradual acceleration of an object to full speed and concludes by gradually decelerating to a stop.
@@ -100,7 +100,7 @@
By using the native driver, we send everything about the animation to native before starting the animation, allowing native code to perform the animation on the UI thread without having to go through the bridge on every frame. Once the animation has started, the JS thread can be blocked without affecting the animation.
You can use the native driver by specifying useNativeDriver: true in your animation configuration. See the Animations guide to learn more.
Animatable components
-
Only animatable components can be animated. These special components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
+
Only animatable components can be animated. These unique components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
Animated.sequence() starts the animations in order, waiting for each to complete before starting the next.
Animated.stagger() starts animations in order and in parallel, but with successive delays.
-
Animations can also be chained together simply by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
+
Animations can also be chained together by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
By default, if one animation is stopped or interrupted, then all other animations in the group are also stopped.
Combining animated values
You can combine two animated values via addition, subtraction, multiplication, division, or modulo to make a new animated value:
@@ -189,14 +189,14 @@
Animates a value according to an analytical spring model based on damped harmonic oscillation. Tracks velocity state to create fluid motions as the toValue updates, and can be chained together.
Config is an object that may have the following options.
Note that you can only define one of bounciness/speed, tension/friction, or stiffness/damping/mass, but not more than one:
-
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
+
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
speed: Controls speed of the animation. Default 12.
bounciness: Controls bounciness. Default 8.
-
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation primitive.
+
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation.
stiffness: The spring stiffness coefficient. Default 100.
damping: Defines how the spring’s motion should be damped due to the forces of friction. Default 10.
@@ -297,7 +297,7 @@
forkEvent()
staticforkEvent(event, listener)
-
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a simple javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
+
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
The Animated library is designed to make animations fluid, powerful, and easy to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and simple start/stop methods to control time-based animation execution.
-
The simplest workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
The Animated library is designed to make animations fluid, powerful, and painless to build and maintain. Animated focuses on declarative relationships between inputs and outputs, with configurable transforms in between, and start/stop methods to control time-based animation execution.
+
The most basic workflow for creating an animation is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates via animations using Animated.timing():
Animated.timing(// Animate value over timethis.state.fadeAnim,// The value to drive
@@ -90,7 +90,7 @@
Animated provides three types of animation types. Each animation type provides a particular animation curve that controls how your values animate from their initial value to the final value:
Animated.decay() starts with an initial velocity and gradually slows to a stop.
In most cases, you will be using timing(). By default, it uses a symmetric easeInOut curve that conveys the gradual acceleration of an object to full speed and concludes by gradually decelerating to a stop.
@@ -100,7 +100,7 @@
By using the native driver, we send everything about the animation to native before starting the animation, allowing native code to perform the animation on the UI thread without having to go through the bridge on every frame. Once the animation has started, the JS thread can be blocked without affecting the animation.
You can use the native driver by specifying useNativeDriver: true in your animation configuration. See the Animations guide to learn more.
Animatable components
-
Only animatable components can be animated. These special components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
+
Only animatable components can be animated. These unique components do the magic of binding the animated values to the properties, and do targeted native updates to avoid the cost of the react render and reconciliation process on every frame. They also handle cleanup on unmount so they are safe by default.
Animated.sequence() starts the animations in order, waiting for each to complete before starting the next.
Animated.stagger() starts animations in order and in parallel, but with successive delays.
-
Animations can also be chained together simply by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
+
Animations can also be chained together by setting the toValue of one animation to be another Animated.Value. See Tracking dynamic values in the Animations guide.
By default, if one animation is stopped or interrupted, then all other animations in the group are also stopped.
Combining animated values
You can combine two animated values via addition, subtraction, multiplication, division, or modulo to make a new animated value:
@@ -189,14 +189,14 @@
Animates a value according to an analytical spring model based on damped harmonic oscillation. Tracks velocity state to create fluid motions as the toValue updates, and can be chained together.
Config is an object that may have the following options.
Note that you can only define one of bounciness/speed, tension/friction, or stiffness/damping/mass, but not more than one:
-
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
+
The friction/tension or bounciness/speed options match the spring model in Facebook Pop, Rebound, and Origami.
speed: Controls speed of the animation. Default 12.
bounciness: Controls bounciness. Default 8.
-
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation primitive.
+
Specifying stiffness/damping/mass as parameters makes Animated.spring use an analytical spring model based on the motion equations of a damped harmonic oscillator. This behavior is slightly more precise and faithful to the physics behind spring dynamics, and closely mimics the implementation in iOS's CASpringAnimation.
stiffness: The spring stiffness coefficient. Default 100.
damping: Defines how the spring’s motion should be damped due to the forces of friction. Default 10.
@@ -297,7 +297,7 @@
forkEvent()
staticforkEvent(event, listener)
-
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a simple javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
+
Advanced imperative API for snooping on animated events that are passed in through props. It permits to add a new javascript listener to an existing AnimatedEvent. If animatedEvent is a javascript listener, it will merge the 2 listeners into a single one, and if animatedEvent is null/undefined, it will assign the javascript listener directly. Use values directly where possible.
Add a handler to AppState changes by listening to the change event type and providing the handler
-
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and just use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
+
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
Add a handler to AppState changes by listening to the change event type and providing the handler
-
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and just use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
+
TODO: now that AppState is a subclass of NativeEventEmitter, we could deprecate addEventListener and removeEventListener and use addListener and listener.remove() directly. That will be a breaking change though, as both the method and event names are different (addListener events are currently required to be globally unique).
AsyncStorage is a simple, unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
+
AsyncStorage is an unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.
On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. On Android, AsyncStorage will use either RocksDB or SQLite based on what is available.
-
The AsyncStorage JavaScript code is a simple facade that provides a clear JavaScript API, real Error objects, and simple non-multi functions. Each method in the API returns a Promise object.
+
The AsyncStorage JavaScript code is a facade that provides a clear JavaScript API, real Error objects, and non-multi functions. Each method in the API returns a Promise object.
AsyncStorage is a simple, unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
+
AsyncStorage is an unencrypted, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.
It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.
On iOS, AsyncStorage is backed by native code that stores small values in a serialized dictionary and larger values in separate files. On Android, AsyncStorage will use either RocksDB or SQLite based on what is available.
-
The AsyncStorage JavaScript code is a simple facade that provides a clear JavaScript API, real Error objects, and simple non-multi functions. Each method in the API returns a Promise object.
+
The AsyncStorage JavaScript code is a facade that provides a clear JavaScript API, real Error objects, and non-multi functions. Each method in the API returns a Promise object.
In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.
Introduction
React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and its own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If an ancestor component relies on the state of its descendant, one should pass down a callback to be used by the descendant to update the ancestor.
-
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.
+
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some specific, cross-language mechanisms that would allow us to pass information between them.
Properties
Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.
Passing properties from native to React Native
@@ -66,7 +66,7 @@ mReactRootView.Passing properties from React Native to native
-
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then just use them in React Native as if the component was an ordinary React Native component.
+
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then use them in React Native as if the component was an ordinary React Native component.
Limits of properties
The main drawback of cross-language properties is that they do not support callbacks, which would allow us to handle bottom-up data bindings. Imagine you have a small RN view that you want to be removed from the native parent view as a result of a JS action. There is no way to do that with props, as the information would need to go bottom-up.
Although we have a flavor of cross-language callbacks (described here), these callbacks are not always the thing we need. The main problem is that they are not intended to be passed as properties. Rather, this mechanism allows us to trigger a native action from JS, and handle the result of that action in JS.
In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.
Introduction
React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and its own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If an ancestor component relies on the state of its descendant, one should pass down a callback to be used by the descendant to update the ancestor.
-
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.
+
The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some specific, cross-language mechanisms that would allow us to pass information between them.
Properties
Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.
Passing properties from native to React Native
@@ -66,7 +66,7 @@ mReactRootView.Passing properties from React Native to native
-
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then just use them in React Native as if the component was an ordinary React Native component.
+
The problem exposing properties of native components is covered in detail in this article. In short, properties that are to be reflected in JavaScript needs to be exposed as setter method annotated with @ReactProp, then use them in React Native as if the component was an ordinary React Native component.
Limits of properties
The main drawback of cross-language properties is that they do not support callbacks, which would allow us to handle bottom-up data bindings. Imagine you have a small RN view that you want to be removed from the native parent view as a result of a JS action. There is no way to do that with props, as the information would need to go bottom-up.
Although we have a flavor of cross-language callbacks (described here), these callbacks are not always the thing we need. The main problem is that they are not intended to be passed as properties. Rather, this mechanism allows us to trigger a native action from JS, and handle the result of that action in JS.
Provides an initial value that will change when the user starts selecting a date. It is useful for simple use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
+
Provides an initial value that will change when the user starts selecting a date. It is useful for use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
Provides an initial value that will change when the user starts selecting a date. It is useful for simple use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
+
Provides an initial value that will change when the user starts selecting a date. It is useful for use-cases where you do not want to deal with listening to events and updating the date prop to keep the controlled state in sync. The controlled state has known bugs which causes it to go out of sync with native. The initialDate prop is intended to allow you to have native be source of truth.
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is both efficient and easy to use if you have fixed size items, for example:
+
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is efficient if you have fixed size items, for example:
getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is both efficient and easy to use if you have fixed size items, for example:
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getItemLayout is an optional optimization that allows skipping the measurement of dynamic content if you know the size (height or width) of items ahead of time. getItemLayout is efficient if you have fixed size items, for example:
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, simply enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
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Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
First, ensure you're using at least version 0.60.4 of React Native.
If you have an existing app based on an earlier version of React Native, you will have to upgrade it first. See Upgrading to new React Native Versions for how to do this. Make especially sure that all changes to android/app/build.gradle have been applied, as detailed by the React Native upgrade helper. After upgrading the app, make sure everything works before trying to switch to Hermes.
@@ -95,7 +95,7 @@
$ react-native run-android
Confirming Hermes is in use
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If you've just created a new app from scratch you should see if Hermes is enabled in the welcome view:
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If you've recently created a new app from scratch you should see if Hermes is enabled in the welcome view:
A HermesInternal global variable will be available in JavaScript that can be used to verify that Hermes is in use:
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, simply enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
+
Hermes is an open-source JavaScript engine optimized for running React Native apps on Android. For many apps, enabling Hermes will result in improved start-up time, decreased memory usage, and smaller app size. At this time Hermes is an opt-in React Native feature, and this guide explains how to enable it.
First, ensure you're using at least version 0.60.4 of React Native.
If you have an existing app based on an earlier version of React Native, you will have to upgrade it first. See Upgrading to new React Native Versions for how to do this. Make especially sure that all changes to android/app/build.gradle have been applied, as detailed by the React Native upgrade helper. After upgrading the app, make sure everything works before trying to switch to Hermes.
@@ -95,7 +95,7 @@
$ react-native run-android
Confirming Hermes is in use
-
If you've just created a new app from scratch you should see if Hermes is enabled in the welcome view:
+
If you've recently created a new app from scratch you should see if Hermes is enabled in the welcome view:
A HermesInternal global variable will be available in JavaScript that can be used to verify that Hermes is in use:
A common feature request from developers familiar with the web is background-image. To handle this use case, you can use the <ImageBackground> component, which has the same props as <Image>, and add whatever children to it you would like to layer on top of it.
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You might not want to use <ImageBackground> in some cases, since the implementation is very simple. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
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You might not want to use <ImageBackground> in some cases, since the implementation is basic. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
Note that you must specify some width and height style attributes.
A common feature request from developers familiar with the web is background-image. To handle this use case, you can use the <ImageBackground> component, which has the same props as <Image>, and add whatever children to it you would like to layer on top of it.
-
You might not want to use <ImageBackground> in some cases, since the implementation is very simple. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
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You might not want to use <ImageBackground> in some cases, since the implementation is basic. Refer to <ImageBackground>'s source code for more insight, and create your own custom component when needed.
Note that you must specify some width and height style attributes.
A component which enables customization of the keyboard input accessory view on iOS. The input accessory view is displayed above the keyboard whenever a TextInput has focus. This component can be used to create custom toolbars.
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To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A simple example:
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To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A basic example:
A component which enables customization of the keyboard input accessory view on iOS. The input accessory view is displayed above the keyboard whenever a TextInput has focus. This component can be used to create custom toolbars.
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To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A simple example:
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To use this component wrap your custom toolbar with the InputAccessoryView component, and set a nativeID. Then, pass that nativeID as the inputAccessoryViewID of whatever TextInput you desire. A basic example:
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
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position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
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If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
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If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always just relative to the parent.
+
position in React Native is similar to regular CSS, but everything is set to relative by default, so absolute positioning is always relative to the parent.
If you want to position a child using specific numbers of logical pixels relative to its parent, set the child to have absolute position.
-
If you want to position a child relative to something that is not its parent, just don't use styles for that. Use the component tree.
+
If you want to position a child relative to something that is not its parent, don't use styles for that. Use the component tree.
React Native is not only for Android and iOS - there are community-supported projects that bring it to other platforms, such as:
React Native Windows - React Native support for Microsoft's Universal Windows Platform (UWP) and the Windows Presentation Foundation (WPF)
React Native DOM - An experimental, comprehensive port of React Native to the web. (Not to be confused with React Native Web, which has different goals)
React Native is not only for Android and iOS - there are community-supported projects that bring it to other platforms, such as:
React Native Windows - React Native support for Microsoft's Universal Windows Platform (UWP) and the Windows Presentation Foundation (WPF)
React Native DOM - An experimental, comprehensive port of React Native to the web. (Not to be confused with React Native Web, which has different goals)
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize basic multi-touch gestures.
By default, PanResponder holds an InteractionManager handle to block long-running JS events from interrupting active gestures.
It provides a predictable wrapper of the responder handlers provided by the gesture responder system. For each handler, it provides a new gestureState object alongside the native event object:
@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state. Simply replace the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
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@param {object} config Enhanced versions of all of the responder callbacks that provide not only the typical ResponderSyntheticEvent, but also the PanResponder gesture state, by replacing the word Responder with PanResponder in each of the typical onResponder* callbacks. For example, the config object would look like:
PanResponder reconciles several touches into a single gesture. It makes single-touch gestures resilient to extra touches, and can be used to recognize simple multi-touch gestures.
