最终运行效果：

image.png

点击flutter和android界面的Text（TextView）之后的效果显示：

image.png

android代码：

• Java代码

public class MainActivity extends AppCompatActivity {

    FlutterEngine mFlutter2Engine;
    FlutterView   mFlutter2View;
    MethodChannel mFlutter2MethodChannel;
    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        tv = findViewById(R.id.tv);
        tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mFlutter2MethodChannel != null) {
                    //点击button2，安卓通过消息通道调用flutter方法
                    mFlutter2MethodChannel.invokeMethod("getFlutterMethod", null, new MethodChannel.Result() {
                        @Override
                        public void success(Object result) {
                            if (result != null) {
                                String str = result.toString();
                                tv.setText(str);

                                System.out.println("android调用Flutter - getFlutterMethod");
                            }
                        }

                        @Override
                        public void error(String errorCode, String errorMessage, Object errorDetails) {

                        }

                        @Override
                        public void notImplemented() {

                        }
                    });
                }
            }
        });
        initFlutterEngine();
        mFlutter2View = createFlutterView();
        mFlutter2View.attachToFlutterEngine(mFlutter2Engine);
    }

    private FlutterView createFlutterView() {
        FlutterView flutterView = new FlutterView(this);
        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        RelativeLayout rl = findViewById(R.id.rl);
        rl.addView(flutterView, lp);
        rl.setVisibility(View.INVISIBLE);
        FlutterUiDisplayListener listener = new FlutterUiDisplayListener() {
            @Override
            public void onFlutterUiDisplayed() {
                rl.setVisibility(View.VISIBLE);
            }

            @Override
            public void onFlutterUiNoLongerDisplayed() {

            }
        };
        flutterView.addOnFirstFrameRenderedListener(listener);
        return flutterView;
    }

    private void initFlutterEngine() {
        mFlutter2Engine = FlutterEngineCache.getInstance().get("flutter2");
        if (mFlutter2Engine == null) {
            mFlutter2Engine = new FlutterEngine(this);
            initChannel(mFlutter2Engine);
            mFlutter2Engine.getDartExecutor().executeDartEntrypoint(
                    DartExecutor.DartEntrypoint.createDefault()
            );
            FlutterEngineCache.getInstance().put("flutter2", mFlutter2Engine);
        }
    }

    /**
     * 创建flutter消息通道
     * @param flutter2Engine
     */
    private void initChannel(FlutterEngine flutter2Engine) {
        mFlutter2MethodChannel = new MethodChannel(flutter2Engine.getDartExecutor(), "flutter2/flutter2Java");
        mFlutter2MethodChannel.setMethodCallHandler(new MethodChannel.MethodCallHandler() {
            @Override
            public void onMethodCall(MethodCall call, MethodChannel.Result result) {
                if (call == null || result == null) {
                    if (result != null) {
                        result.error("-1", "MethodCall is null", new Exception("MethodCall is null"));
                    }
                    return;
                }
                //flutter调用android的getJavaMethod方法
                if ("getJavaMethod".equals(call.method)) {
                    result.success("flutter调用android - getJavaMethod方法成功");
                } else {
                    result.success(" unKnow method");
                }
            }
        });
    }


    @Override
    protected void onResume() {
        super.onResume();
        mFlutter2Engine.getLifecycleChannel().appIsResumed();
    }

    @Override
    protected void onStart() {
        super.onStart();
    }

    @Override
    protected void onRestart() {
        super.onRestart();
    }

    @Override
    protected void onPause() {
        super.onPause();
        mFlutter2Engine.getLifecycleChannel().appIsInactive();
    }

    @Override
    protected void onStop() {
        super.onStop();
        mFlutter2Engine.getLifecycleChannel().appIsPaused();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        FlutterEngineCache.getInstance().remove("flutter2");
        mFlutter2View = null;
    }
}

• android xml代码

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        >

        <RelativeLayout
            android:id="@+id/rl"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            >


        </RelativeLayout>
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            >
            <TextView
                android:id="@+id/tv"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"

                android:text="我是android界面的TextView">

            </TextView>



        </RelativeLayout>
    </LinearLayout>

flutter代码

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

void main() => runApp(MyHomePage());


class MyHomePage extends StatefulWidget {

  @override
  _MyHomePageState createState() => _MyHomePageState();

}

class _MyHomePageState extends State<MyHomePage> {

  String str ='我是flutter界面Text';

  static const platform = const MethodChannel("flutter2/flutter2Java");
  Future<Null> _getJavaMethod() async {
    try {
      print("flutter调用android - getJavaMethod");
      // 在通道上调用此方法
      final String intValue = await platform.invokeMethod("getJavaMethod");
      str = '$intValue';
    } on Exception catch (e) {
      str = "Failed to getJavaMethod: '${e.toString()}'.";
    }
    setState(() {
      print("dart -setState");
    });
  }

  //flutter设置回调
  Future<dynamic> _platformCallHandler(MethodCall call) async {
    switch (call.method) {
      case "getFlutterMethod":
        return "android调用Flutter - getFlutterMethod'方法成功";
      default:
        return "call.method not getFlutterName";
    }
  }


  @override
  Widget build(BuildContext context) {
    platform.setMethodCallHandler(_platformCallHandler);

    return new MaterialApp(
      home: Scaffold(
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              InkWell(
                child: Text(str,
                ),
                onTap: ()async {
                  _getJavaMethod();
                },
              ),
            ],
          ),
        ),
      )
    );

  }
}

如果想要跳转到不同的flutter界面，只需要在创建FlutterEngine的时候，设置不同的路由标志就行了，然后在flutter界面根据设置的路由标志，加载不同的widget。

代码如下：

• android

 private void initFlutterEngine() {
        mFlutter2Engine = FlutterEngineCache.getInstance().get("flutter2");
        if (mFlutter2Engine == null) {
            mFlutter2Engine = new FlutterEngine(this);
            //设置跳转不同的flutter界面的路由标志
            mFlutter2Engine.getNavigationChannel().setInitialRoute("route2");
            initChannel(mFlutter2Engine);
            mFlutter2Engine.getDartExecutor().executeDartEntrypoint(
                    DartExecutor.DartEntrypoint.createDefault()
            );
            FlutterEngineCache.getInstance().put("flutter2", mFlutter2Engine);
        }
    }

• flutter

void main(){

//flutter入口代码，通过路由标识，加载不同的布局<br>
  var defaultRouteName = window.defaultRouteName;
  if("route1" == defaultRouteName){
    runApp(MyHomePage());

  } else if("route2" == defaultRouteName){
    runApp(Page1());
  }else if("route3" == defaultRouteName){
    runApp(Page2());

  }



}