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121 lines
27 KiB
Markdown
---
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id: view
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title: View
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category: Components
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permalink: docs/view.html
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---
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<div><div><p>The most fundamental component for building a UI, <code>View</code> is a container that supports layout with
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<a href="docs/flexbox.html" target="_blank">flexbox</a>, <a href="docs/style.html" target="_blank">style</a>,
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<a href="docs/handling-touches.html" target="_blank">some touch handling</a>, and
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<a href="docs/accessibility.html" target="_blank">accessibility</a> controls. <code>View</code> maps directly to the
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native view equivalent on whatever platform React Native is running on, whether that is a
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<code>UIView</code>, <code><div></code>, <code>android.view</code>, etc.</p><p><code>View</code> is designed to be nested inside other views and can have 0 to many children of any type.</p><p>This example creates a <code>View</code> that wraps two colored boxes and a text component in a row with
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padding.</p><div class="prism language-javascript"><span class="token keyword">class</span> <span class="token class-name">ViewColoredBoxesWithText</span> <span class="token keyword">extends</span> <span class="token class-name">Component</span> <span class="token punctuation">{</span>
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<span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
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<span class="token keyword">return</span> <span class="token punctuation">(</span>
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<span class="token operator"><</span>View style<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">{</span>flexDirection<span class="token punctuation">:</span> <span class="token string">'row'</span><span class="token punctuation">,</span> height<span class="token punctuation">:</span> <span class="token number">100</span><span class="token punctuation">,</span> padding<span class="token punctuation">:</span> <span class="token number">20</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token operator">></span>
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<span class="token operator"><</span>View style<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">{</span>backgroundColor<span class="token punctuation">:</span> <span class="token string">'blue'</span><span class="token punctuation">,</span> flex<span class="token punctuation">:</span> <span class="token number">0.3</span><span class="token punctuation">}</span><span class="token punctuation">}</span> <span class="token operator">/</span><span class="token operator">></span>
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<span class="token operator"><</span>View style<span class="token operator">=</span><span class="token punctuation">{</span><span class="token punctuation">{</span>backgroundColor<span class="token punctuation">:</span> <span class="token string">'red'</span><span class="token punctuation">,</span> flex<span class="token punctuation">:</span> <span class="token number">0.5</span><span class="token punctuation">}</span><span class="token punctuation">}</span> <span class="token operator">/</span><span class="token operator">></span>
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<span class="token operator"><</span>Text<span class="token operator">></span>Hello World<span class="token operator">!</span><span class="token operator"><</span><span class="token operator">/</span>Text<span class="token operator">></span>
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<span class="token operator"><</span><span class="token operator">/</span>View<span class="token operator">></span>
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<span class="token punctuation">)</span><span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">}</span></div><blockquote><p><code>View</code>s are designed to be used with <a href="docs/style.html" target="_blank"><code>StyleSheet</code></a> for clarity
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and performance, although inline styles are also supported.</p></blockquote><h3><a class="anchor" name="synthetic-touch-events"></a>Synthetic Touch Events <a class="hash-link" href="docs/view.html#synthetic-touch-events">#</a></h3><p>For <code>View</code> responder props (e.g., <code>onResponderMove</code>), the synthetic touch event passed to them
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are of the following form:</p><ul><li><code>nativeEvent</code><ul><li><code>changedTouches</code> - Array of all touch events that have changed since the last event.</li><li><code>identifier</code> - The ID of the touch.</li><li><code>locationX</code> - The X position of the touch, relative to the element.</li><li><code>locationY</code> - The Y position of the touch, relative to the element.</li><li><code>pageX</code> - The X position of the touch, relative to the root element.</li><li><code>pageY</code> - The Y position of the touch, relative to the root element.</li><li><code>target</code> - The node id of the element receiving the touch event.</li><li><code>timestamp</code> - A time identifier for the touch, useful for velocity calculation.</li><li><code>touches</code> - Array of all current touches on the screen.</li></ul></li></ul></div><h3><a class="anchor" name="props"></a>Props <a class="hash-link" href="docs/view.html#props">#</a></h3><div class="props"><div class="prop"><h4 class="propTitle"><a class="anchor" name="viewproptypes"></a><a href="docs/viewproptypes.html#props">ViewPropTypes props...</a> <a class="hash-link" href="docs/view.html#viewproptypes">#</a></h4></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessibilitylabel"></a>accessibilityLabel?: <span class="propType">node</span> <a class="hash-link" href="docs/view.html#accessibilitylabel">#</a></h4><div><p>Overrides the text that's read by the screen reader when the user interacts
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with the element. By default, the label is constructed by traversing all the
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children and accumulating all the <code>Text</code> nodes separated by space.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessible"></a>accessible?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#accessible">#</a></h4><div><p>When <code>true</code>, indicates that the view is an accessibility element. By default,
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all the touchable elements are accessible.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="hitslop"></a>hitSlop?: <span class="propType">{top: number, left: number, bottom: number, right: number}</span> <a class="hash-link" href="docs/view.html#hitslop">#</a></h4><div><p>This defines how far a touch event can start away from the view.
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Typical interface guidelines recommend touch targets that are at least
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30 - 40 points/density-independent pixels.</p><p>For example, if a touchable view has a height of 20 the touchable height can be extended to
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40 with <code>hitSlop={{top: 10, bottom: 10, left: 0, right: 0}}</code></p><blockquote><p>The touch area never extends past the parent view bounds and the Z-index
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of sibling views always takes precedence if a touch hits two overlapping
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views.</p></blockquote></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="nativeid"></a>nativeID?: <span class="propType">string</span> <a class="hash-link" href="docs/view.html#nativeid">#</a></h4><div><p>Used to locate this view from native classes.</p><blockquote><p>This disables the 'layout-only view removal' optimization for this view!</p></blockquote></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onaccessibilitytap"></a>onAccessibilityTap?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onaccessibilitytap">#</a></h4><div><p>When <code>accessible</code> is true, the system will try to invoke this function
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when the user performs accessibility tap gesture.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onlayout"></a>onLayout?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onlayout">#</a></h4><div><p>Invoked on mount and layout changes with:</p><p><code>{nativeEvent: { layout: {x, y, width, height}}}</code></p><p>This event is fired immediately once the layout has been calculated, but
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the new layout may not yet be reflected on the screen at the time the
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event is received, especially if a layout animation is in progress.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onmagictap"></a>onMagicTap?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onmagictap">#</a></h4><div><p>When <code>accessible</code> is <code>true</code>, the system will invoke this function when the
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user performs the magic tap gesture.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onmoveshouldsetresponder"></a>onMoveShouldSetResponder?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onmoveshouldsetresponder">#</a></h4><div><p>Does this view want to "claim" touch responsiveness? This is called for every touch move on
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the <code>View</code> when it is not the responder.</p><p><code>View.props.onMoveShouldSetResponder: (event) => [true | false]</code>, where <code>event</code> is a
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synthetic touch event as described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onmoveshouldsetrespondercapture"></a>onMoveShouldSetResponderCapture?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onmoveshouldsetrespondercapture">#</a></h4><div><p>If a parent <code>View</code> wants to prevent a child <code>View</code> from becoming responder on a move,
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it should have this handler which returns <code>true</code>.</p><p><code>View.props.onMoveShouldSetResponderCapture: (event) => [true | false]</code>, where <code>event</code> is a
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synthetic touch event as described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onrespondergrant"></a>onResponderGrant?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onrespondergrant">#</a></h4><div><p>The View is now responding for touch events. This is the time to highlight and show the user
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what is happening.</p><p><code>View.props.onResponderGrant: (event) => {}</code>, where <code>event</code> is a synthetic touch event as
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described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onrespondermove"></a>onResponderMove?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onrespondermove">#</a></h4><div><p>The user is moving their finger.</p><p><code>View.props.onResponderMove: (event) => {}</code>, where <code>event</code> is a synthetic touch event as
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described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onresponderreject"></a>onResponderReject?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onresponderreject">#</a></h4><div><p>Another responder is already active and will not release it to that <code>View</code> asking to be
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the responder.</p><p><code>View.props.onResponderReject: (event) => {}</code>, where <code>event</code> is a synthetic touch event as
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described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onresponderrelease"></a>onResponderRelease?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onresponderrelease">#</a></h4><div><p>Fired at the end of the touch.</p><p><code>View.props.onResponderRelease: (event) => {}</code>, where <code>event</code> is a synthetic touch event as
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described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onresponderterminate"></a>onResponderTerminate?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onresponderterminate">#</a></h4><div><p>The responder has been taken from the <code>View</code>. Might be taken by other views after a call to
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<code>onResponderTerminationRequest</code>, or might be taken by the OS without asking (e.g., happens
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with control center/ notification center on iOS)</p><p><code>View.props.onResponderTerminate: (event) => {}</code>, where <code>event</code> is a synthetic touch event as
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described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onresponderterminationrequest"></a>onResponderTerminationRequest?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onresponderterminationrequest">#</a></h4><div><p>Some other <code>View</code> wants to become responder and is asking this <code>View</code> to release its
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responder. Returning <code>true</code> allows its release.</p><p><code>View.props.onResponderTerminationRequest: (event) => {}</code>, where <code>event</code> is a synthetic touch
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event as described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onstartshouldsetresponder"></a>onStartShouldSetResponder?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onstartshouldsetresponder">#</a></h4><div><p>Does this view want to become responder on the start of a touch?</p><p><code>View.props.onStartShouldSetResponder: (event) => [true | false]</code>, where <code>event</code> is a
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synthetic touch event as described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="onstartshouldsetrespondercapture"></a>onStartShouldSetResponderCapture?: <span class="propType">function</span> <a class="hash-link" href="docs/view.html#onstartshouldsetrespondercapture">#</a></h4><div><p>If a parent <code>View</code> wants to prevent a child <code>View</code> from becoming responder on a touch start,
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it should have this handler which returns <code>true</code>.</p><p><code>View.props.onStartShouldSetResponderCapture: (event) => [true | false]</code>, where <code>event</code> is a
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synthetic touch event as described above.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="pointerevents"></a>pointerEvents?: <span class="propType">enum('box-none', 'none', 'box-only', 'auto')</span> <a class="hash-link" href="docs/view.html#pointerevents">#</a></h4><div><p>Controls whether the <code>View</code> can be the target of touch events.</p><ul><li><code>'auto'</code>: The View can be the target of touch events.</li><li><code>'none'</code>: The View is never the target of touch events.</li><li><code>'box-none'</code>: The View is never the target of touch events but it's
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subviews can be. It behaves like if the view had the following classes
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in CSS:<div class="prism language-javascript"><span class="token punctuation">.</span>box<span class="token operator">-</span>none <span class="token punctuation">{</span>
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pointer<span class="token operator">-</span>events<span class="token punctuation">:</span> none<span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">.</span>box<span class="token operator">-</span>none <span class="token operator">*</span> <span class="token punctuation">{</span>
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pointer<span class="token operator">-</span>events<span class="token punctuation">:</span> all<span class="token punctuation">;</span>
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<span class="token punctuation">}</span></div></li><li><code>'box-only'</code>: The view can be the target of touch events but it's
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subviews cannot be. It behaves like if the view had the following classes
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in CSS:<div class="prism language-javascript"><span class="token punctuation">.</span>box<span class="token operator">-</span>only <span class="token punctuation">{</span>
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pointer<span class="token operator">-</span>events<span class="token punctuation">:</span> all<span class="token punctuation">;</span>
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<span class="token punctuation">}</span>
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<span class="token punctuation">.</span>box<span class="token operator">-</span>only <span class="token operator">*</span> <span class="token punctuation">{</span>
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pointer<span class="token operator">-</span>events<span class="token punctuation">:</span> none<span class="token punctuation">;</span>
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<span class="token punctuation">}</span></div><blockquote><p>Since <code>pointerEvents</code> does not affect layout/appearance, and we are
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already deviating from the spec by adding additional modes, we opt to not
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include <code>pointerEvents</code> on <code>style</code>. On some platforms, we would need to
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implement it as a <code>className</code> anyways. Using <code>style</code> or not is an
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implementation detail of the platform.</p></blockquote></li></ul></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="removeclippedsubviews"></a>removeClippedSubviews?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#removeclippedsubviews">#</a></h4><div><p>This is a special performance property exposed by <code>RCTView</code> and is useful
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for scrolling content when there are many subviews, most of which are
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offscreen. For this property to be effective, it must be applied to a
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view that contains many subviews that extend outside its bound. The
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subviews must also have <code>overflow: hidden</code>, as should the containing view
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(or one of its superviews).</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="style"></a>style?: <span class="propType">stylePropType</span> <a class="hash-link" href="docs/view.html#style">#</a></h4></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="testid"></a>testID?: <span class="propType">string</span> <a class="hash-link" href="docs/view.html#testid">#</a></h4><div><p>Used to locate this view in end-to-end tests.</p><blockquote><p>This disables the 'layout-only view removal' optimization for this view!</p></blockquote></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessibilitycomponenttype"></a><span class="platform">android</span>accessibilityComponentType?: <span class="propType">AccessibilityComponentTypes</span> <a class="hash-link" href="docs/view.html#accessibilitycomponenttype">#</a></h4><div><p>Indicates to accessibility services to treat UI component like a
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native one. Works for Android only.</p><p>Possible values are one of:</p><ul><li><code>'none'</code></li><li><code>'button'</code></li><li><code>'radiobutton_checked'</code></li><li><code>'radiobutton_unchecked'</code></li></ul></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessibilityliveregion"></a><span class="platform">android</span>accessibilityLiveRegion?: <span class="propType">enum('none', 'polite', 'assertive')</span> <a class="hash-link" href="docs/view.html#accessibilityliveregion">#</a></h4><div><p>Indicates to accessibility services whether the user should be notified
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when this view changes. Works for Android API >= 19 only.
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Possible values:</p><ul><li><code>'none'</code> - Accessibility services should not announce changes to this view.</li><li><code>'polite'</code>- Accessibility services should announce changes to this view.</li><li><code>'assertive'</code> - Accessibility services should interrupt ongoing speech to immediately announce changes to this view.</li></ul><p>See the <a href="http://developer.android.com/reference/android/view/View.html#attr_android:accessibilityLiveRegion" target="_blank">Android <code>View</code> docs</a>
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for reference.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="collapsable"></a><span class="platform">android</span>collapsable?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#collapsable">#</a></h4><div><p>Views that are only used to layout their children or otherwise don't draw
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anything may be automatically removed from the native hierarchy as an
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optimization. Set this property to <code>false</code> to disable this optimization and
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ensure that this <code>View</code> exists in the native view hierarchy.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="importantforaccessibility"></a><span class="platform">android</span>importantForAccessibility?: <span class="propType">enum('auto', 'yes', 'no', 'no-hide-descendants')</span> <a class="hash-link" href="docs/view.html#importantforaccessibility">#</a></h4><div><p>Controls how view is important for accessibility which is if it
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fires accessibility events and if it is reported to accessibility services
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that query the screen. Works for Android only.</p><p>Possible values:</p><ul><li><code>'auto'</code> - The system determines whether the view is important for accessibility -
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default (recommended).</li><li><code>'yes'</code> - The view is important for accessibility.</li><li><code>'no'</code> - The view is not important for accessibility.</li><li><code>'no-hide-descendants'</code> - The view is not important for accessibility,
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nor are any of its descendant views.</li></ul><p>See the <a href="http://developer.android.com/reference/android/R.attr.html#importantForAccessibility" target="_blank">Android <code>importantForAccessibility</code> docs</a>
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for reference.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="needsoffscreenalphacompositing"></a><span class="platform">android</span>needsOffscreenAlphaCompositing?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#needsoffscreenalphacompositing">#</a></h4><div><p>Whether this <code>View</code> needs to rendered offscreen and composited with an alpha
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in order to preserve 100% correct colors and blending behavior. The default
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(<code>false</code>) falls back to drawing the component and its children with an alpha
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applied to the paint used to draw each element instead of rendering the full
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component offscreen and compositing it back with an alpha value. This default
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may be noticeable and undesired in the case where the <code>View</code> you are setting
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an opacity on has multiple overlapping elements (e.g. multiple overlapping
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<code>View</code>s, or text and a background).</p><p>Rendering offscreen to preserve correct alpha behavior is extremely
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expensive and hard to debug for non-native developers, which is why it is
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not turned on by default. If you do need to enable this property for an
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animation, consider combining it with renderToHardwareTextureAndroid if the
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view <strong>contents</strong> are static (i.e. it doesn't need to be redrawn each frame).
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If that property is enabled, this View will be rendered off-screen once,
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saved in a hardware texture, and then composited onto the screen with an alpha
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each frame without having to switch rendering targets on the GPU.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="rendertohardwaretextureandroid"></a><span class="platform">android</span>renderToHardwareTextureAndroid?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#rendertohardwaretextureandroid">#</a></h4><div><p>Whether this <code>View</code> should render itself (and all of its children) into a
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single hardware texture on the GPU.</p><p>On Android, this is useful for animations and interactions that only
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modify opacity, rotation, translation, and/or scale: in those cases, the
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view doesn't have to be redrawn and display lists don't need to be
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re-executed. The texture can just be re-used and re-composited with
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different parameters. The downside is that this can use up limited video
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memory, so this prop should be set back to false at the end of the
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interaction/animation.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessibilitytraits"></a><span class="platform">ios</span>accessibilityTraits?: <span class="propType"><span><span>AccessibilityTraits, </span><span>[AccessibilityTraits]</span></span></span> <a class="hash-link" href="docs/view.html#accessibilitytraits">#</a></h4><div><p>Provides additional traits to screen reader. By default no traits are
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provided unless specified otherwise in element.</p><p>You can provide one trait or an array of many traits.</p><p>Possible values for <code>AccessibilityTraits</code> are:</p><ul><li><code>'none'</code> - The element has no traits.</li><li><code>'button'</code> - The element should be treated as a button.</li><li><code>'link'</code> - The element should be treated as a link.</li><li><code>'header'</code> - The element is a header that divides content into sections.</li><li><code>'search'</code> - The element should be treated as a search field.</li><li><code>'image'</code> - The element should be treated as an image.</li><li><code>'selected'</code> - The element is selected.</li><li><code>'plays'</code> - The element plays sound.</li><li><code>'key'</code> - The element should be treated like a keyboard key.</li><li><code>'text'</code> - The element should be treated as text.</li><li><code>'summary'</code> - The element provides app summary information.</li><li><code>'disabled'</code> - The element is disabled.</li><li><code>'frequentUpdates'</code> - The element frequently changes its value.</li><li><code>'startsMedia'</code> - The element starts a media session.</li><li><code>'adjustable'</code> - The element allows adjustment over a range of values.</li><li><code>'allowsDirectInteraction'</code> - The element allows direct touch interaction for VoiceOver users.</li><li><code>'pageTurn'</code> - Informs VoiceOver that it should scroll to the next page when it finishes reading the contents of the element.</li></ul><p>See the <a href="docs/accessibility.html#accessibilitytraits-ios" target="_blank">Accessibility guide</a>
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for more information.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="accessibilityviewismodal"></a><span class="platform">ios</span>accessibilityViewIsModal?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#accessibilityviewismodal">#</a></h4><div><p>A value indicating whether VoiceOver should ignore the elements
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within views that are siblings of the receiver.
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Default is <code>false</code>.</p><p>See the <a href="docs/accessibility.html#accessibilitytraits-ios" target="_blank">Accessibility guide</a>
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for more information.</p></div></div><div class="prop"><h4 class="propTitle"><a class="anchor" name="shouldrasterizeios"></a><span class="platform">ios</span>shouldRasterizeIOS?: <span class="propType">bool</span> <a class="hash-link" href="docs/view.html#shouldrasterizeios">#</a></h4><div><p>Whether this <code>View</code> should be rendered as a bitmap before compositing.</p><p>On iOS, this is useful for animations and interactions that do not
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modify this component's dimensions nor its children; for example, when
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translating the position of a static view, rasterization allows the
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renderer to reuse a cached bitmap of a static view and quickly composite
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it during each frame.</p><p>Rasterization incurs an off-screen drawing pass and the bitmap consumes
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memory. Test and measure when using this property.</p></div></div></div><span><h3><a class="anchor" name="type-definitions"></a>Type Definitions <a class="hash-link" href="docs/view.html#type-definitions">#</a></h3><div class="props"><div class="prop"><h4 class="propTitle"><a class="anchor" name="props"></a>Props <a class="hash-link" href="docs/view.html#props">#</a></h4><strong>Type:</strong><br>ViewProps</div></div></span></div> |