diff --git a/releases/next/docs/debugging.html b/releases/next/docs/debugging.html index 8dc861cc5ff..dd14d4c265e 100644 --- a/releases/next/docs/debugging.html +++ b/releases/next/docs/debugging.html @@ -1,4 +1,4 @@ -Debugging
React Nativenext

The Basics

Guides

Guides (iOS)

Guides (Apple TV)

Guides (Android)

components

APIs

Debugging #

Enabling Keyboard Shortcuts #

React Native supports a few keyboard shortcuts in the iOS Simulator. They are described below. To enable them, open the Hardware menu, select Keyboard, and make sure that "Connect Hardware Keyboard" is checked.

Accessing the In-App Developer Menu #

You can access the developer menu by shaking your device or by selecting "Shake Gesture" inside the Hardware menu in the iOS Simulator. You can also use the Command⌘ + D keyboard shortcut when your app is running in the iPhone Simulator, or Command⌘ + M when running in an Android emulator.

The Developer Menu is disabled in release (production) builds.

Reloading JavaScript #

Instead of recompiling your app every time you make a change, you can reload your app's JavaScript code instantly. To do so, select "Reload" from the Developer Menu. You can also press Command⌘ + R in the iOS Simulator, or press R twice on Android emulators.

Automatic reloading #

You can speed up your development times by having your app reload automatically any time your code changes. Automatic reloading can be enabled by selecting "Enable Live Reload" from the Developer Menu.

You may even go a step further and keep your app running as new versions of your files are injected into the JavaScript bundle automatically by enabling Hot Reloading from the Developer Menu. This will allow you to persist the app's state through reloads.

There are some instances where hot reloading cannot be implemented perfectly. If you run into any issues, use a full reload to reset your app.

You will need to rebuild your app for changes to take effect in certain situations:

  • You have added new resources to your native app's bundle, such as an image in Images.xcassets on iOS or the res/drawable folder on Android.
  • You have modified native code (Objective-C/Swift on iOS or Java/C++ on Android).

In-app Errors and Warnings #

Errors and warnings are displayed inside your app in development builds.

Errors #

In-app errors are displayed in a full screen alert with a red background inside your app. This screen is known as a RedBox. You can use console.error() to manually trigger one.

Warnings #

Warnings will be displayed on screen with a yellow background. These alerts are known as YellowBoxes. Click on the alerts to show more information or to dismiss them.

As with a RedBox, you can use console.warn() to trigger a YellowBox.

YellowBoxes can be disabled during development by using console.disableYellowBox = true;. Specific warnings can be ignored programmatically by setting an array of prefixes that should be ignored: console.ignoredYellowBox = ['Warning: ...'];.

In CI/Xcode, YellowBoxes can also be disabled by setting the IS_TESTING environment variable.

RedBoxes and YellowBoxes are automatically disabled in release (production) builds.

Chrome Developer Tools #

To debug the JavaScript code in Chrome, select "Debug JS Remotely" from the Developer Menu. This will open a new tab at http://localhost:8081/debugger-ui.

Select Tools → Developer Tools from the Chrome Menu to open the Developer Tools. You may also access the DevTools using keyboard shortcuts (Command⌘ + Option⌥ + I on Mac, Ctrl + Shift + I on Windows). You may also want to enable Pause On Caught Exceptions for a better debugging experience.

Note: the React Developer Tools Chrome extension does not work with React Native, but you can use its standalone version instead. Read this section to learn how.

Debugging using a custom JavaScript debugger #

To use a custom JavaScript debugger in place of Chrome Developer Tools, set the REACT_DEBUGGER environment variable to a command that will start your custom debugger. You can then select "Debug JS Remotely" from the Developer Menu to start debugging.

The debugger will receive a list of all project roots, separated by a space. For example, if you set REACT_DEBUGGER="node /path/to/launchDebugger.js --port 2345 --type ReactNative", then the command node /path/to/launchDebugger.js --port 2345 --type ReactNative /path/to/reactNative/app will be used to start your debugger.

Custom debugger commands executed this way should be short-lived processes, and they shouldn't produce more than 200 kilobytes of output.

React Developer Tools #

With React Native 0.43 or higher, you can use the standalone version of React Developer Tools to debug the React component hierarchy. To use it, install the react-devtools package globally:

npm install -g react-devtools

Now run react-devtools from the terminal to launch the standalone DevTools app:

react-devtools

React DevTools

It should connect to your simulator within a few seconds.

Note: if you prefer to avoid global installations, you can add react-devtools as a project dependency. With Yarn, you can run yarn add --dev react-devtools, and then run yarn react-devtools from your project folder to open the DevTools. With npm, you can run npm install --save-dev react-devtools, add "react-devtools": "react-devtools" to the scripts section in your package.json, and then run npm run react-devtools from your project folder to open the DevTools.

Integration with React Native Inspector #

You can open the in-app developer menu and choose "Show Inspector". It will bring up an overlay that lets you tap on any UI element and see information about it:

React Native Inspector

However, when react-devtools is running, Inspector will enter a special collapsed mode, and instead use the DevTools as primary UI. In this mode, clicking on something in the simulator will bring up the relevant components in the DevTools:

React DevTools Inspector Integration

You can choose "Hide Inspector" in the same menu to exit this mode.

Inspecting Component Instances #

When debugging JavaScript in Chrome, you can inspect the props and state of the React components in the browser console.

First, follow the instructions for debugging in Chrome to open the Chrome console.

Make sure that the dropdown in the top left corner of the Chrome console says debuggerWorker.js. This step is essential.

Then select a React component in React DevTools. There is a search box at the top that helps you find one by name. As soon as you select it, it will be available as $r in the Chrome console, letting you inspect its props, state, and instance properties.

React DevTools Chrome Console Integration

Performance Monitor #

You can enable a performance overlay to help you debug performance problems by selecting "Perf Monitor" in the Developer Menu.

+Debugging
React Nativenext

The Basics

Guides

Guides (iOS)

Guides (Apple TV)

Guides (Android)

components

APIs

Debugging #

Enabling Keyboard Shortcuts #

React Native supports a few keyboard shortcuts in the iOS Simulator. They are described below. To enable them, open the Hardware menu, select Keyboard, and make sure that "Connect Hardware Keyboard" is checked.

Accessing the In-App Developer Menu #

You can access the developer menu by shaking your device or by selecting "Shake Gesture" inside the Hardware menu in the iOS Simulator. You can also use the ⌘D keyboard shortcut when your app is running in the iOS Simulator, or ⌘M when running in an Android emulator.

The Developer Menu is disabled in release (production) builds.

Reloading JavaScript #

Instead of recompiling your app every time you make a change, you can reload your app's JavaScript code instantly. To do so, select "Reload" from the Developer Menu. You can also press ⌘R in the iOS Simulator, or tap R twice on Android emulators.

Automatic reloading #

You can speed up your development times by having your app reload automatically any time your code changes. Automatic reloading can be enabled by selecting "Enable Live Reload" from the Developer Menu.

You may even go a step further and keep your app running as new versions of your files are injected into the JavaScript bundle automatically by enabling Hot Reloading from the Developer Menu. This will allow you to persist the app's state through reloads.

There are some instances where hot reloading cannot be implemented perfectly. If you run into any issues, use a full reload to reset your app.

You will need to rebuild your app for changes to take effect in certain situations:

  • You have added new resources to your native app's bundle, such as an image in Images.xcassets on iOS or the res/drawable folder on Android.
  • You have modified native code (Objective-C/Swift on iOS or Java/C++ on Android).

In-app Errors and Warnings #

Errors and warnings are displayed inside your app in development builds.

Errors #

In-app errors are displayed in a full screen alert with a red background inside your app. This screen is known as a RedBox. You can use console.error() to manually trigger one.

Warnings #

Warnings will be displayed on screen with a yellow background. These alerts are known as YellowBoxes. Click on the alerts to show more information or to dismiss them.

As with a RedBox, you can use console.warn() to trigger a YellowBox.

YellowBoxes can be disabled during development by using console.disableYellowBox = true;. Specific warnings can be ignored programmatically by setting an array of prefixes that should be ignored: console.ignoredYellowBox = ['Warning: ...'];.

In CI/Xcode, YellowBoxes can also be disabled by setting the IS_TESTING environment variable.

RedBoxes and YellowBoxes are automatically disabled in release (production) builds.

Chrome Developer Tools #

To debug the JavaScript code in Chrome, select "Debug JS Remotely" from the Developer Menu. This will open a new tab at http://localhost:8081/debugger-ui.

Select Tools → Developer Tools from the Chrome Menu to open the Developer Tools. You may also access the DevTools using keyboard shortcuts (⌘⌥I on macOS, Ctrl Shift I on Windows). You may also want to enable Pause On Caught Exceptions for a better debugging experience.

Note: the React Developer Tools Chrome extension does not work with React Native, but you can use its standalone version instead. Read this section to learn how.

Debugging using a custom JavaScript debugger #

To use a custom JavaScript debugger in place of Chrome Developer Tools, set the REACT_DEBUGGER environment variable to a command that will start your custom debugger. You can then select "Debug JS Remotely" from the Developer Menu to start debugging.

The debugger will receive a list of all project roots, separated by a space. For example, if you set REACT_DEBUGGER="node /path/to/launchDebugger.js --port 2345 --type ReactNative", then the command node /path/to/launchDebugger.js --port 2345 --type ReactNative /path/to/reactNative/app will be used to start your debugger.

Custom debugger commands executed this way should be short-lived processes, and they shouldn't produce more than 200 kilobytes of output.

React Developer Tools #

You can use the standalone version of React Developer Tools to debug the React component hierarchy. To use it, install the react-devtools package globally:

npm install -g react-devtools

Now run react-devtools from the terminal to launch the standalone DevTools app:

react-devtools

React DevTools

It should connect to your simulator within a few seconds.

Note: if you prefer to avoid global installations, you can add react-devtools as a project dependency. Add the react-devtools package to your project using npm install --save-dev react-devtools, then add "react-devtools": "react-devtools" to the scripts section in your package.json, and then run npm run react-devtools from your project folder to open the DevTools.

Integration with React Native Inspector #

Open the in-app developer menu and choose "Show Inspector". It will bring up an overlay that lets you tap on any UI element and see information about it:

React Native Inspector

However, when react-devtools is running, Inspector will enter a special collapsed mode, and instead use the DevTools as primary UI. In this mode, clicking on something in the simulator will bring up the relevant components in the DevTools:

React DevTools Inspector Integration

You can choose "Hide Inspector" in the same menu to exit this mode.

Inspecting Component Instances #

When debugging JavaScript in Chrome, you can inspect the props and state of the React components in the browser console.

First, follow the instructions for debugging in Chrome to open the Chrome console.

Make sure that the dropdown in the top left corner of the Chrome console says debuggerWorker.js. This step is essential.

Then select a React component in React DevTools. There is a search box at the top that helps you find one by name. As soon as you select it, it will be available as $r in the Chrome console, letting you inspect its props, state, and instance properties.

React DevTools Chrome Console Integration

Performance Monitor #

You can enable a performance overlay to help you debug performance problems by selecting "Perf Monitor" in the Developer Menu.

Debugging in Ejected Apps #

-

Accessing console logs #

Note: if you're using Create React Native App, these already appear in the same terminal output as the packager.

You can display the console logs for an iOS or Android app by using the following commands in a terminal while the app is running:

$ react-native log-ios -$ react-native log-android

You may also access these through Debug → Open System Log... in the iOS Simulator or by running adb logcat *:S ReactNative:V ReactNativeJS:V in a terminal while an Android app is running on a device or emulator.

Debugging on a device with Chrome Developer Tools #

Note: if you're using Create React Native App, this is configured for you already.

On iOS devices, open the file RCTWebSocketExecutor.m and change "localhost" to the IP address of your computer, then select "Debug JS Remotely" from the Developer Menu.

On Android 5.0+ devices connected via USB, you can use the adb command line tool to setup port forwarding from the device to your computer:

adb reverse tcp:8081 tcp:8081

Alternatively, select "Dev Settings" from the Developer Menu, then update the "Debug server host for device" setting to match the IP address of your computer.

If you run into any issues, it may be possible that one of your Chrome extensions is interacting in unexpected ways with the debugger. Try disabling all of your extensions and re-enabling them one-by-one until you find the problematic extension.

Debugging with Stetho on Android #

  1. In android/app/build.gradle, add these lines in the dependencies section:

    compile 'com.facebook.stetho:stetho:1.3.1' +

    Accessing console logs #

    You can display the console logs for an iOS or Android app by using the following commands in a terminal while the app is running:

    $ react-native log-ios +$ react-native log-android

    You may also access these through Debug → Open System Log... in the iOS Simulator or by running adb logcat *:S ReactNative:V ReactNativeJS:V in a terminal while an Android app is running on a device or emulator.

    If you're using Create React Native App, console logs already appear in the same terminal output as the packager.

    Debugging on a device with Chrome Developer Tools #

    If you're using Create React Native App, this is configured for you already.

    On iOS devices, open the file RCTWebSocketExecutor.m and change "localhost" to the IP address of your computer, then select "Debug JS Remotely" from the Developer Menu.

    On Android 5.0+ devices connected via USB, you can use the adb command line tool to setup port forwarding from the device to your computer:

    adb reverse tcp:8081 tcp:8081

    Alternatively, select "Dev Settings" from the Developer Menu, then update the "Debug server host for device" setting to match the IP address of your computer.

    If you run into any issues, it may be possible that one of your Chrome extensions is interacting in unexpected ways with the debugger. Try disabling all of your extensions and re-enabling them one-by-one until you find the problematic extension.

    Debugging with Stetho on Android #

    1. In android/app/build.gradle, add these lines in the dependencies section:

      compile 'com.facebook.stetho:stetho:1.3.1' compile 'com.facebook.stetho:stetho-okhttp3:1.3.1'

    2. In android/app/src/main/java/com/{yourAppName}/MainApplication.java, add the following imports:

      import com.facebook.react.modules.network.ReactCookieJarContainer; import com.facebook.stetho.Stetho; import okhttp3.OkHttpClient; @@ -29,7 +29,7 @@ import java.util.addNetworkInterceptor(new StethoInterceptor()) .build(); OkHttpClientProvider.replaceOkHttpClient(client); -}

    3. Run react-native run-android

    4. In a new chrome tab, open : chrome://inspect, click on 'Inspect device' (the one followed by "Powered by Stetho")

    Debugging native code #

    When working with native code (e.g. when writing native modules) you can launch the app from Android Studio or Xcode and take advantage of the debugging features (setup breakpoints, etc.) as you would in case of building a standard native app.

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React Nativenext

The Basics

Guides

Guides (iOS)

Guides (Apple TV)

Guides (Android)

components

APIs

Running On Device #

It's always a good idea to test your app on an actual device before releasing it to your users. This document will guide you through the necessary steps to run your React Native app on a device.

+Running On Device
React Nativenext

The Basics

Guides

Guides (iOS)

Guides (Apple TV)

Guides (Android)

components

APIs

Running On Device #

It's always a good idea to test your app on an actual device before releasing it to your users. This document will guide you through the necessary steps to run your React Native app on a device and to get it ready for production.

- Mobile OS: - iOS - Android Development OS: macOS Linux Windows + Target OS: + iOS + Android +
-

A Mac is required in order to build your app for iOS devices.

+

Running your app on iOS devices #

A Mac is required in order to build your app for iOS devices. Alternatively, you can refer to the Quick Start instructions to learn how to build your app using Create React Native App, which will allow you to run your app using the Expo client app.

-

Running your app on iOS devices #

Register for a Apple developer account if you don't have one yet.

Connect your device to your Mac using a USB to Lightning cable. Navigate to the ios folder in your project, then open the .xcodeproj file within it using Xcode.

Select your app in the Project Navigator and look for the "General" tab. Go to "Signing" and make sure your Apple developer account is selected.

Open the "Product" menu from Xcode's menubar, then go to "Destination". Look for and select your device from the list. Xcode will then register your device for development.

If everything is set up correctly, your device will be listed as the build target in the Xcode toolbar. You can now press the Build and run button or select "Run" from the "Product" menu. Your app will launch on your device shortly.

If you run into any issues, please take a look at Apple's Launching Your App on a Device docs.

+

Running your app on iOS devices #

Register for a Apple developer account if you don't have one yet.

1. Plug in your device via USB #

Connect your iOS device to your Mac using a USB to Lightning cable. Navigate to the ios folder in your project, then open the .xcodeproj file within it using Xcode.

If this is your first time running an app on your iOS device, you may need to register your device for development. Open the Product menu from Xcode's menubar, then go to Destination. Look for and select your device from the list. Xcode will then register your device for development.

2. Configure code signing #

Select your project in the Xcode Project Navigator, then select your main target (it should share the same name as your project). Look for the "General" tab. Go to "Signing" and make sure your Apple developer account or team is selected under the Team dropdown.

Repeat this step for the Tests target in your project.

3. Build and Run your app #

If everything is set up correctly, your device will be listed as the build target in the Xcode toolbar, and it will also appear in the Devices pane (⇧⌘2). You can now press the Build and run button (⌘R) or select Run from the Product menu. Your app will launch on your device shortly.

If you run into any issues, please take a look at Apple's Launching Your App on a Device docs.

Running your app on Android devices #

1. Enable Debugging over USB #

Most Android devices can only install and run apps downloaded from Google Play, by default. You will need to enable USB Debugging on your device in order to install your app during development.

To enable USB debugging on your device, you will first need to enable the "Developer options" menu by going to Settings → About phone and then tapping the Build number row at the bottom seven times. You can then go back to Settings → Developer options to enable "USB debugging".

2. Plug in your device via USB #

Let's now set up an Android device to run our React Native projects. Go ahead and plug in your device via USB to your development machine.

@@ -65,11 +66,11 @@ emulator-5554 offline # Google emulator -

Connecting to the development server #

You can also iterate quickly on a device using the development server. You only have to be on the same Wi-Fi network as your computer. Enable Live reloading from the Developer menu and your app will reload whenever your JavaScript code has changed.

If you have any issues, ensure that your Mac and device are on the same network and can reach each other. Many open wireless networks with captive portals are configured to prevent devices from reaching other devices on the network. You may use your device's Personal Hotspot feature in this case.

+

Connecting to the development server #

You can also iterate quickly on a device using the development server. You only have to be on the same Wi-Fi network as your computer. Shake your device to open the Developer menu, then enable Live Reload. Your app will reload whenever your JavaScript code has changed.

If you have any issues, ensure that your Mac and device are on the same network and can reach each other. Many open wireless networks with captive portals are configured to prevent devices from reaching other devices on the network. You may use your device's Personal Hotspot feature in this case.

Connecting to the development server #

You can also iterate quickly on a device by connecting to the development server running on your development machine. There are several ways of accomplishing this, depending on whether you have access to a USB cable or a Wi-Fi network.

Method 1: Using adb reverse (recommended) #

-

You can use this method if your device is running Android 5.0 (Lollipop), it has USB debugging enabled, and it is connected via USB to your development machine.

+

You can use this method if your device is running Android 5.0 (Lollipop) or newer, it has USB debugging enabled, and it is connected via USB to your development machine.

Run the following in a command prompt:

$ adb reverse tcp:8081 tcp:8081

You can now enable Live reloading from the Developer menu. Your app will reload whenever your JavaScript code has changed.

Method 2: Connect via Wi-Fi #

You can also connect to the development server over Wi-Fi. You'll first need to install the app on your device using a USB cable, but once that has been done you can debug wirelessly by following these instructions. You'll need your development machine's current IP address before proceeding.

@@ -81,7 +82,9 @@ emulator-5554 offline # Google emulator
  1. Make sure your laptop and your phone are on the same Wi-Fi network.
  2. Open your React Native app on your device.
  3. You'll see a red screen with an error. This is OK. The following steps will fix that.
  4. Open the in-app Developer menu.
  5. Go to Dev Settings → Debug server host for device.
  6. Type in your machine's IP address and the port of the local dev server (e.g. 10.0.1.1:8081).
  7. Go back to the Developer menu and select Reload JS.

You can now enable Live reloading from the Developer menu. Your app will reload whenever your JavaScript code has changed.

-

Building your app for production #

You have built a great app using React Native, and you are now itching to release it in the App Store. The process is the same as any other native iOS app, with some additional considerations to take into account.

Building an app for distribution in the App Store requires using the Release scheme in Xcode. To do this, go to Product → Scheme → Edit Scheme (cmd + <), make sure you're in the Run tab from the side, and set the Build Configuration dropdown to Release.

Apps built for Release will automatically disable the in-app Developer menu, which will prevent your users from inadvertently accessing the menu in production. It will also load the JavaScript locally, so you can put the app on a device and test whilst not connected to the computer.

Hint

You can also use the React Native CLI to perform this operation using the option --configuration with the value Release (e.g. react-native run-ios --configuration Release).

Once built for release, you'll be able to distribute the app to beta testers and submit the app to the App Store.

App Transport Security #

App Transport Security is a security feature, added in iOS 9, that rejects all HTTP requests that are not sent over HTTPS. This can result in HTTP traffic being blocked, including the developer React Native server.

ATS is disabled by default in projects generated using the React Native CLI in order to make development easier. You should re-enable ATS prior to building your app for production by removing the NSAllowsArbitraryLoads entry from your Info.plist file in the ios/ folder.

To learn more about how to configure ATS on your own Xcode projects, see this post on ATS.