import 'package:fluttertoast/fluttertoast.dart';  //提示第三方插件

DateTime _lastPressedAt; //上次点击时间

main.dart-MyApp中：
home: WillPopScope( // 监听返回键WidgetonWillPop: () async { // 点击返回键即触发该事件if (_lastPressedAt == null) { //首次点击提示...信息Fluttertoast.showToast(msg: "双击退出程序...",gravity: ToastGravity.BOTTOM,timeInSecForIos: 1,backgroundColor: Colors.grey[400],textColor: Colors.white,fontSize: ScreenUtil().setWidth(12),);}if (_lastPressedAt == null || DateTime.now().difference(_lastPressedAt) >  Duration(seconds: 1)) {//两次点击间隔超过1秒则重新计时_lastPressedAt = DateTime.now();return false; // 不退出}return true;  //退出},child: Pages(),
),

import 'package:flutter_smart_park/untils/android_back_desktop.dart';home: WillPopScope(onWillPop: () async {AndroidBackTop.backDeskTop();return false;},child: configProvide.token == '0' ? UserLogIn() : Pages(),
),

import 'package:flutter/services.dart';
import 'package:flutter/material.dart';

class AndroidBackTop {//初始化通信管道-设置退出到手机桌面static const String CHANNEL = "android/back/desktop";//设置回退到手机桌面static Future<bool> backDeskTop() async {final platform = MethodChannel(CHANNEL);//通知安卓返回,到手机桌面try {final bool out = await platform.invokeMethod('backDesktop');if (out) debugPrint('返回到桌面');} on PlatformException catch (e) {debugPrint("通信失败(设置回退到安卓手机桌面:设置失败)");print(e.toString());}return Future.value(false);}
}

import android.os.Bundle;
import android.view.KeyEvent;import io.flutter.app.FlutterActivity; import io.flutter.plugins.GeneratedPluginRegistrant;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel; 

public class MainActivity extends FlutterActivity {　//通讯名称,回到手机桌面private  final String CHANNEL = "android/back/desktop";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);GeneratedPluginRegistrant.registerWith(this);

　　　　MethodChannel(getFlutterView(), CHANNEL).setMethodCallHandler(MethodChannel.MethodCallHandler() {@Overridepublic void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {if (methodCall.method.equals("backDesktop")) {result.success(true);moveTaskToBack(false);  //是否关闭} }});}
}

　添加相关依赖

import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;

　申明变量CHANNEL，值与定义触发事件包名相同，以上android_back_desktop为例：

private  final String CHANNEL = "android/back/desktop";

　在MethodChannel的中调用.setMethodCallHandler() 方法，需要一个MethodCallHandler 对象，是一个匿名内部类，有一个方法onMethodCall,在Flutter发送请求事，onMethodCall方法会执行。

public class MainActivity extends FlutterActivity {private static final String CHANNEL = "android_back_desktop";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);GeneratedPluginRegistrant.registerWith(this);MethodChannel(getFlutterView(), CHANNEL).setMethodCallHandler(MethodCallHandler() {@Overridepublic void onMethodCall(MethodCall methodCall, Result result) {}});}
}

onMethodCall方法中有两个参数 MethodCall 和 result，MethodCall 中有关当前请求的信息，例如调用方法的名字changeLife;Result用于发送信息给Flutter。

在onMethodCall中判断当前请求是否为changeLife,如果是通过result 的 success 返回信息：Life Changed .

public void onMethodCall(MethodCall methodCall, Result result) {if (methodCall.method.equals("backDesktop")){String message ="Life Changed";result.success(message);}...