javascript-如何在一个屏幕而不是整个应用程序中处理退出应用程序-React Native？

概述我在BackHandler上有问题,问题是当运行该应用程序并转到“注册”屏幕并在我的手机上触摸后方时,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后方时,我需要返回到每个BackBack.exitApp()上的上一个屏幕；运行,尽管我写的是routname是SignUp,但只是退出

我在BackHandler上有问题,问题是

当运行该应用程序并转到“注册”屏幕并在我的手机上触摸后方时,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后方时,我需要返回到每个BackBack.exitApp()上的上一个屏幕；运行,尽管我写的是routname是SignUp,但只是退出应用程序而不是其他屏幕

这是我的代码

注册

    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 want to exit?",        [          {            text: "No",            onPress: () => console.log("Cancel pressed"),            style: "cancel"          },          { text: "Yes", onPress: () => BackHandler.exitApp() }        ],        { cancelable: false }      );      return true;    } else {      return false;    }  };      render() {....}    }

路线

import { createStackNavigator, createAppContainer } from "react-navigation";import React from "react";import { VIEw } from "react-native";import Splash from "../screens/Splash";import Home from "../screens/Home";import SignUp from "../screens/SignUp";import SignIn from "../screens/SignIn";import Forgetpassword from "../screens/Forgetpassword";const Routes = createStackNavigator(  {    Splash: {      screen: Splash,      navigationoptions: {        header: null      }    },    SignUp: {      screen: SignUp,      navigationoptions: () => ({        // header: null        Title: "Sign Up",        headerleft: null,        headerTintcolor: "#fc0301",        headerStyle: {          borderBottomcolor: "white"        },        headerTitleStyle: {          color: "#fc0301",          textAlign: "center",          flex: 1,          elevation: 0,          FontSize: 25,          justifyContent: "center"        }      })    },    SignIn: {      screen: SignIn,      navigationoptions: {        Title: "Sign In",        headerRight: <VIEw />,        headerTintcolor: "#fc0301",        headerStyle: {          borderBottomcolor: "white"        },        headerTitleStyle: {          color: "#fc0301",          textAlign: "center",          flex: 1,          elevation: 0,          FontSize: 25,          justifyContent: "center"        }      }    },    Forgetpassword: {      screen: Forgetpassword,      navigationoptions: {        header: null      }    },    Home: {      screen: Home,      navigationoptions: {        header: null      }    }  },  {    initialRoutename: "Splash"  });export default createAppContainer(Routes);

解决方法:

您可以在调用警报之前检查屏幕是否聚焦,而不用从导航中检查routename.

更新的代码可能如下所示.

if (this.props.navigation.isFocused()) {    Alert.alert(    "Exit App",    "Do you want to exit?",    [      {        text: "No",        onPress: () => console.log("Cancel pressed"),        style: "cancel"      },      { text: "Yes", onPress: () => BackHandler.exitApp() }    ],    { cancelable: false }    );}

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