How to know if a react native app goes to background?

Question

Is it possible to know if a RN app has gone to background? Any callback or trigger?

If I listen to componentDidUnmount or componentWillUnmount of the screen I'm on, it will only be fired if I go back/forth to another screen

Answer 1

You can listen to the appState event. From https://facebook.github.io/react-native/docs/appstate.html:

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>     );   }  } 

By the way, this will always say 'Current state is: active', because that is the only state in which the app will be visible for the user.