相关疑难解决方法(0)

我已经把android后退按钮退出我的主屏幕中的反应本机应用程序中的应用程序功能.但是当我在其他屏幕上按下android后退按钮时,它也会被调用.

componentDidMount() {

    if (Platform.OS == "android") {
        BackHandler.addEventListener('hardwareBackPress', this.handleBackButton);                           
  }
    this._setupGoogleSignin();           
    this._getUserDetails();
    const { navigate } = this.props.navigation;
    console.log("object url is", this.state.postsArray[0].url);

}

handleBackButton = () => {               
    Alert.alert(
        'Exit App',
        'Exiting the application?', [{
            text: 'Cancel',
            onPress: () => console.log('Cancel Pressed'),
            style: 'cancel'
        }, {
            text: 'OK',
            onPress: () => BackHandler.exitApp()
        }, ], {
            cancelable: false
        }
     )
     return true;
   }
componentWillUnmount() {
    BackHandler.removeEventListener('hardwareBackPress', this.handleBackButton);
  }

我对BackHandler有一些问题，问题是

当运行应用程序并转到比方说注册屏幕并触摸我手机的背面时，他们将运行该功能并显示警报以进行确认，但是现在当我转到任何其他屏幕并触摸背面时，我需要每次返回 BackHandler.exitApp() 就回到上一个屏幕；运行，虽然我写如果路由名称是注册只是退出应用程序而不是其他屏幕

这是我的代码

报名

    import React from "react";
    import {
      Text,
      TextInput,
      ActivityIndicator,
      View,
      KeyboardAvoidingView,
      ScrollView,
      Image,
      TouchableOpacity,
      BackHandler,
      Alert
    } from "react-native";
    export default class signUp extends React.Component {
      constructor(props) {
        super(props);

      }

      componentDidMount() {
        BackHandler.addEventListener("hardwareBackPress", this.backPressed);
      }

      componentWillUnmount() {
        BackHandler.removeEventListener("hardwareBackPress", this.backPressed);
      }
      backPressed = () => {
    let { routeName } = this.props.navigation.state;
    console.log("route is :  " + routeName);

    if (routeName == "SignUp") {
      console.log("ROUTE :  " + routeName);
      Alert.alert(
        "Exit App",
        "Do you …