AppState
AppState
can tell you if the app is in the foreground or background, and notify you when the state changes.
AppState is frequently used to determine the intent and proper behavior when handling push notifications.
App States
active
- The app is running in the foregroundbackground
- The app is running in the background. The user is either in another app or on the home screeninactive
- This is a state that occurs when transitioning between foreground & background, and during periods of inactivity such as entering the Multitasking view or in the event of an incoming call
For more information, see Apple's documentation
Basic Usage
To see the current state, you can check AppState.currentState
, which will be kept up-to-date. However, currentState
will be null at launch while AppState
retrieves it over the bridge.
import React, {Component} from 'react'
import {AppState, Text} from 'react-native'
class AppStateExample extends Component {
state = {
appState: AppState.currentState
}
componentDidMount() {
AppState.addEventListener('change', this._handleAppStateChange);
}
componentWillUnmount() {
AppState.removeEventListener('change', this._handleAppStateChange);
}
_handleAppStateChange = (nextAppState) => {
if (this.state.appState.match(/inactive|background/) && nextAppState === 'active') {
console.log('App has come to the foreground!')
}
this.setState({appState: nextAppState});
}
render() {
return (
<Text>Current state is: {this.state.appState}</Text>
);
}
}
This example will only ever appear to say "Current state is: active" because the app is only visible to the user when in the active
state, and the null state will happen only momentarily.
Methods
Properties
Reference
Methods
addEventListener()
addEventListener(type, handler);
Add a handler to AppState changes by listening to the change
event type and providing the handler
Parameters:
Name | Type | Required | Description |
---|---|---|---|
type | string | Yes | |
handler | function | Yes |
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).
removeEventListener()
removeEventListener(type, handler);
Remove a handler by passing the change
event type and the handler
Parameters:
Name | Type | Required | Description |
---|---|---|---|
type | string | Yes | |
handler | function | Yes |
Properties
currentState
AppState.currentState;