實(shí)際開發(fā)中有這么一個(gè)需求，當(dāng)停留在首頁(yè)的時(shí)候 點(diǎn)擊 Android的返回鍵，提示再次點(diǎn)擊退出，直接上代碼

  import React from "react";
  import { BackHandler } from "react-native";
  class ScreenWithCustomBackBehavior extends React.Component {
    _didFocusSubscription;
    _willBlurSubscription;
    constructor(props) {
      super(props);
    this._didFocusSubscription = props.navigation.addListener('didFocus', payload =>
      BackHandler.addEventListener('hardwareBackPress', this.onBackButtonPressAndroid)
  ) ;
}

componentDidMount() {
    this._willBlurSubscription = this.props.navigation.addListener('willBlur', payload =>
     BackHandler.removeEventListener('hardwareBackPress', this.onBackButtonPressAndroid)
  );
}

onBackButtonPressAndroid = () => {
    if (判斷條件) {
    //需要操作的事件(如：再次點(diǎn)擊退出應(yīng)用)
  return true;
    } else {
  return false;
  }
} ;

componentWillUnmount() {
  this._didFocusSubscription && this._didFocusSubscription.remove();
  this._willBlurSubscription && this._willBlurSubscription.remove();
}

render() {
// ...
  }
}