84 lines
1.6 KiB
Markdown
84 lines
1.6 KiB
Markdown
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---
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id: backhandler
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title: BackHandler
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layout: docs
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category: APIs
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permalink: docs/backhandler.html
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next: cameraroll
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previous: backhandler
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---
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Detect hardware button presses for back navigation.
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Android: Detect hardware back button presses, and programmatically invoke the default back button
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functionality to exit the app if there are no listeners or if none of the listeners return true.
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tvOS: Detect presses of the menu button on the TV remote. (Still to be implemented:
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programmatically disable menu button handling
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functionality to exit the app if there are no listeners or if none of the listeners return true.)
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iOS: Not applicable.
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The event subscriptions are called in reverse order (i.e. last registered subscription first),
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and if one subscription returns true then subscriptions registered earlier will not be called.
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Example:
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```javascript
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BackHandler.addEventListener('hardwareBackPress', function() {
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// this.onMainScreen and this.goBack are just examples, you need to use your own implementation here
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// Typically you would use the navigator here to go to the last state.
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if (!this.onMainScreen()) {
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this.goBack();
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return true;
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}
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return false;
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});
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```
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### Methods
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- [`exitApp`](docs/backhandler.html#exitapp)
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- [`addEventListener`](docs/backhandler.html#addeventlistener)
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- [`removeEventListener`](docs/backhandler.html#removeeventlistener)
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---
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# Reference
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## Methods
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### `exitApp()`
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```javascript
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static exitApp()
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```
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---
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### `addEventListener()`
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```javascript
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static addEventListener(eventName, handler)
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```
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---
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### `removeEventListener()`
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```javascript
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static removeEventListener(eventName, handler)
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```
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