原生Android调用Flutter的dart方法

约定不等于承诺〃 2022-11-26 07:40 258阅读 0赞

# 先提供完整的代码 #

main.dart

import 'package:flutter/material.dart';
    
    import 'MainPage.dart';
    
    void main(){
      runApp(
         MyApp()
      );
    }
    
    class MyApp extends StatelessWidget {
    
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          debugShowCheckedModeBanner: false,
          title: 'default',
          theme: defaultTheme,
          home: MainPage(),
        );
      }
    }
    
    
    final ThemeData defaultTheme = ThemeData(
        primaryColor: Colors.lightBlue
    );

MainPage.dart

import 'package:flutter/cupertino.dart';
    import 'package:flutter/material.dart';
    import 'package:flutter/services.dart';
    
    class MainPage extends StatefulWidget{
      @override
      MainPageState createState()  => MainPageState();
    }
    
    class MainPageState extends State<MainPage>{
    
      static const _platform = const MethodChannel('toFlutterChannelName');
    
      @override
      void initState() {
        _platform.setMethodCallHandler(flutterMethod);
        super.initState();
      }
    
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          title: 'Flutter调用原生Android的方法',
          debugShowCheckedModeBanner: false,
          home: Scaffold(
            appBar: AppBar(
              title: Text('Flutter调用原生Android的Java方法'),
            ),
            body: Center(
              child:
              RaisedButton(
                child:
                Padding(
                  padding: EdgeInsets.only(left: 20,right: 20,top: 20,bottom: 20),
                  child: Text('点击按钮调用原生Android的Java方法\n，返回值在控制台输出'),
                ),
    
                onPressed: ()async{
                  const platform = const MethodChannel("toJava");
                  String returnValue = await platform.invokeMethod("张三");
                  print("从原生Android的java方法返回的值是："+returnValue);
                },
              )
            )
          ),
        );
      }
    
    
    
      Future<dynamic> flutterMethod(MethodCall methodCall) async{
        switch (methodCall.method) {
          case 'fluMethod':
            print('原生Android调用了flutterMethod方法！！！');
            print('原生Android传递给flutter的参数是：：'+methodCall.arguments);
            break;
        }
      }
    
    }

MainActivity.java

package com.example.flutterTojava;
    
    import android.os.Bundle;
    import android.os.StrictMode;
    
    import io.flutter.embedding.android.FlutterActivity;
    import io.flutter.plugin.common.BinaryMessenger;
    //import io.flutter.app.FlutterActivity;
    import io.flutter.plugin.common.MethodCall;
    import io.flutter.plugin.common.MethodChannel;
    
    public class MainActivity extends FlutterActivity {
    
        private static final String channel = "toJava";
    
        MethodChannel methodChannel_toFlutter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);
            if (android.os.Build.VERSION.SDK_INT > 9) {
                StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
                StrictMode.setThreadPolicy(policy);
            }
    
            //新版的Flutter SDK默认使用的是 import io.flutter.embedding.android.FlutterActivity; 包，
            // 则在MethodChannel方法中的第一个参数填写 getFlutterEngine().getDartExecutor().getBinaryMessenger()
            //如果你使用的Flutter的SDK是旧版本，那么默认的是 import io.flutter.app.FlutterActivity; 包
            // 则MethodChannel方法中的第一个参数填写 getFlutterView()
    
            new MethodChannel(getFlutterEngine().getDartExecutor().getBinaryMessenger(),channel).setMethodCallHandler(
                    new MethodChannel.MethodCallHandler() {
                        @Override
                        public void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {
                            if (methodCall.method!=null) {
                                result.success(toJava(methodCall.method));
                            } else {
                                result.notImplemented();
                            }
                        }
                    }
            );
    
    
            methodChannel_toFlutter = new MethodChannel(
                    getFlutterEngine().getDartExecutor().getBinaryMessenger(), "toFlutterChannelName"
            );
    
        }
    
    
        public String toJava(String name){
            System.out.println("传递的参数是"+name);
            invokeFlutterMethod_toAllFlutter();
            return "您好"+name;
        }
    
        public void invokeFlutterMethod_toAllFlutter(){
            if (this.methodChannel_toFlutter != null) {
                this.methodChannel_toFlutter.invokeMethod("fluMethod", "我是原生Android，我将参数传递给Flutter里面的一个方法", new MethodChannel.Result() {
                    @Override
                    public void success(Object o) {
    
                    }
                    @Override
                    public void error(String s, String s1, Object o) {
                    }
                    @Override
                    public void notImplemented() {
                    }
                });
            }
        }
    
    }

# 下面来解释步骤 #

一、在MainPage类中定义一个MethodChannel常量\_platform, 并在initState()方法中处理Flutter申请要调用的method的值，此时会调用自定义方法flutterMethod

在Flutter代码中：

static const _platform = const MethodChannel('toFlutterChannelName');
    
      @override
      void initState() {
        _platform.setMethodCallHandler(flutterMethod);
        super.initState();
      }

二、定义一个flutterMethod方法

在Flutter代码中：

Future<dynamic> flutterMethod(MethodCall methodCall) async{
        switch (methodCall.method) {
          case 'fluMethod':
            print('原生Android调用了flutterMethod方法！！！');
            print('原生Android传递给flutter的参数是：：'+methodCall.arguments);
            break;
        }
      }

三、在原生Android的MainActivity类中，声明一个MethodChannel的变量，然后在onCreate()方法中，通过这个变量获取通道

public class MainActivity extends FlutterActivity {
    
        MethodChannel methodChannel_toFlutter;
    
        @Override
        protected void onCreate(Bundle savedInstanceState){
             
            super.onCreate(savedInstanceState);
    
             methodChannel_toFlutter = new MethodChannel(
                    getFlutterEngine().getDartExecutor().getBinaryMessenger(),"toFlutterChannelName"
             );
    
        }
    
    }

四、让原生Android调用 invokeFlutterMethod\_toAllFlutter() 方法，这个方法里面实现了 "调用flutter方法的动作"。

您也可以在onCreate() 里面，直接invokeFlutterMethod\_toAllFlutter()调用这个方法，以调用flutter的方法。

public void invokeFlutterMethod_toAllFlutter(){
            if (this.methodChannel_toFlutter != null) {
                this.methodChannel_toFlutter.invokeMethod("fluMethod", "我是原生Android，我将参数传递给Flutter里面的一个方法", new MethodChannel.Result() {
                    @Override
                    public void success(Object o) {
    
                    }
                    @Override
                    public void error(String s, String s1, Object o) {
                    }
                    @Override
                    public void notImplemented() {
                    }
                });
            }
        }

五、测试

![20200810223548705.png][]

[20200810223548705.png]: /images/20221124/cb12c0e9f072411a809de5be72cc9352.png