本文主要尝试解决如下几个问题：

1. 如何在在已经项目加入Flutter
2. 混合跳转
3. 混合栈问题
4. 混合栈数据问题

跳转黑屏是因为debug的缘故，打release包则没有。

1. 如何在在已经项目加入Flutter

直接参考这篇文章Add Flutter to existing apps

2. 混合跳转

首先：Android跳转到Flutter

创建一个FlutterActivity

直接继承FlutterActivity或者自定义一个CustomFlutterActivity，我用的自定义，是做了一些封装和flutter插件注册

public abstract class CustomFlutterActivity extends AppCompatActivity implements FlutterView.Provider, PluginRegistry, FlutterActivityDelegate.ViewFactory {

    private final FlutterActivityDelegate delegate = new FlutterActivityDelegate(this, this);
    private final FlutterActivityEvents eventDelegate;
    private final FlutterView.Provider viewProvider;
    private final PluginRegistry pluginRegistry;

    public CustomFlutterActivity() {
        this.eventDelegate = this.delegate;
        this.viewProvider = this.delegate;
        this.pluginRegistry = this.delegate;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        if (injectRouter())
            ARouter.getInstance().inject(this);
        super.onCreate(savedInstanceState);
        this.eventDelegate.onCreate(savedInstanceState);
        GeneratedPluginRegistrant.registerWith(this);
        registerCustomPlugin(this);
    }

    protected boolean injectRouter() {
        return false;
    }

    //省略部分代码
    .........
    .........
    private static void registerCustomPlugin(PluginRegistry registrar) {

        FlutterPluginJumpToAct.registerWith(registrar.registrarFor(FlutterPluginJumpToAct.CHANNEL));

    }
}

做一个Flutter用的容器，通过容器统一管理需要跳转的Flutter界面

@Route(path = RouterPath.MainPath.MAIN_FLUTTER_CONTAINER, name = "FlutterContainerActivity")
public class FlutterContainerActivity extends CustomFlutterActivity {

    private static String CHANNEL = "com.jzhu.msg/plugin";

    private static int TIME_ONE_SECOND = 1000;

    @Autowired(name = "path")
    String path;

    @Override
    protected boolean injectRouter() {
        return true;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initBasicMessageChannel();
    }

    @Override
    public FlutterView createFlutterView(Context context) {
        WindowManager.LayoutParams matchParent = new WindowManager.LayoutParams(-1, -1);
        FlutterNativeView nativeView = this.createFlutterNativeView();
        FlutterView flutterView = new FlutterView(FlutterContainerActivity.this, (AttributeSet) null, nativeView);
        flutterView.setInitialRoute(path);
        flutterView.setLayoutParams(matchParent);
        this.setContentView(flutterView);
        return flutterView;
    }

    private void initBasicMessageChannel() {
        switch (path) {
            case RouterPath.ModuleFlutterPath.FLUTTER_HOME:
                initHomeBasicMessage();
                break;
            case RouterPath.ModuleFlutterPath.FLUTTER_TEST:
                initTestBasicMessage();
                break;
        }

    }

   private void initTestBasicMessage() {
        BasicMessageChannel channel = new BasicMessageChannel<String>(
                getFlutterView(), CHANNEL, StringCodec.INSTANCE);
        channel.setMessageHandler((o, reply) -> {
            ToastUtils.show((String)o,3000);
            reply.reply("FlutterContainerActivity：回条消息给你");
        });
    
        new Handler().postDelayed(() -> channel.send("FlutterContainerActivity：发条消息给你"), TIME_ONE_SECOND);
    }

    private void initHomeBasicMessage() {
        //todo
    }

}

Flutter提供的页面

void main() {
  runApp(new MaterialApp(
    routes: <String, WidgetBuilder>{
    '/homepage': (BuildContext context) => new MyHomePage(),
    '/testpage': (BuildContext context) => new TestPage(),
  }, home: new MyHomePage()));
}

路由

public interface RouterPath {

    interface  MainPath{
        String MAIN_FLUTTER_CONTAINER = "/main/FlutterContainerActivity";
        String MAIN_TEST= "/main/TestActivity";
    }

    interface  ModuleFlutterPath{
        String FLUTTER_HOME= "/homepage";
        String FLUTTER_TEST= "/testpage";
    }

}

点击跳转

ARouter.getInstance()
               .build(RouterPath.MainPath.MAIN_FLUTTER_CONTAINER)
               .withString("path", RouterPath.ModuleFlutterPath.FLUTTER_HOME)
               .navigation();

最后：Flutter跳转到Android

通过插件实现，用法参考我之前写一篇Flutter知识点: Flutter与原生(Android)的交互

3. 混合栈问题

1. 如果是Android的页面跳转到Android页面，所以就是普通的Activity栈。
2. 如果是Android的页面跳转到Flutter页面，那么都使用了我们的容器FlutterContainerActivity，所以就是普通的Activity栈，这里面遇到个坑，下面会提出并尝试解决。
3. 如果是Flutter的页面跳转到Flutter页面，那么由Flutter自己内部的栈管理。
4. 如果是Flutter的页面跳转到Android页面，那么自己管自己就好啦。

如果你把Flutter的页面全装到到容器FlutterContainerActivity展示，那就都是普通的Activity栈，省事！

混合跳转注意：

1. Android某些页面的启动模式Standard，SingleTop，SingleTask，SingleInstance
2. Flutter页面也存在一些特殊的跳转，popAndPushNamed，pushNamedAndRemoveUntil，popUntil，pushReplacementNamed
   以上需要根据实际情况处理，存在特殊跳转，销毁等逻辑

开发中需要特别需要注意的一个问题：

跳转顺序：Android页面 -> Flutter页面（使用了FlutterContainerActivity）-> Flutter页面（原始）
期望结果：Flutter页面（原始）-> Flutter页面（使用了FlutterContainerActivity）-> Android页面
真实结果：Flutter页面（原始）-> Flutter页面（使用了FlutterContainerActivity）-> Flutter页面（homepage） -> Android页面
得到疑问：我们并没有启动homepage，为什么多了一个homepage？
代码猜想：Flutter栈里初始化了一个homepage， 其他Flutter的页面都在这个栈之上。

void main() {
  runApp(new MaterialApp(
    routes: <String, WidgetBuilder>{
    ............
  }, home: new MyHomePage()));
}

如何解决：使用SystemNavigator.pop()，
Tells the operating system to close the application, or the closest equivalent.
onWillPop参考这篇Flutter学习中的问题记录: 如何监听实体/虚拟返回键和AppBar返回键

class _MyHomePageState extends State<MyHomePage> {
  static const jumpPlugin = const MethodChannel('com.jzhu.jump/plugin');

  Future<Null> _jumpToNative() async {
    Map<String, String> map = {"path": "/main/TestActivity"};

    String result = await jumpPlugin.invokeMethod('jump2act', map);
    print(result);
  }

  Future<bool> _requestPop() {
    SystemNavigator.pop();
    return new Future.value(false);
  }


  @override
  Widget build(BuildContext context) {
    return new WillPopScope(
        child: new Scaffold(
          appBar: new AppBar(
            title: new Text("Home Page"),
          ),
          body: new Center(
            child: new RaisedButton(
                child: new Text("跳到TestActivity"), onPressed: _jumpToNative),
          ),
          // This trailing comma makes auto-formatting nicer for build methods.
        ),
        onWillPop: _requestPop);
  }
}

4. 混合栈数据问题，以插件的方式解决 。

MethodChannel，EventChanneld的数据传输，用法参考我之前写一篇Flutter知识点: Flutter与原生(Android)的交互

主要举例BasicMessageChannel和BinaryMessages

FlutterContainerActivity中初始化，监听，发送

为什么要延迟发送？
因为FlutterView可能还没初始化，这时候无法接收消息

 private static String CHANNEL = "com.jzhu.msg/plugin";
 private static String CHANNEL_BINARY = "com.jzhu.msg.binary/plugin";
 private static int TIME_ONE_SECOND = 1000;

  private void initTestBasicMessage() {
        BasicMessageChannel channel = new BasicMessageChannel<String>(
                getFlutterView(), CHANNEL, StringCodec.INSTANCE);
        channel.setMessageHandler((o, reply) -> {
            ToastUtils.show((String)o,3000);
            reply.reply("FlutterContainerActivity：回条消息给你");
        });
        new Handler().postDelayed(() -> channel.send("FlutterContainerActivity：发条消息给你"), TIME_ONE_SECOND);

        ByteBuffer message = ByteBuffer.allocateDirect(256);
        message.putDouble(3.14);
        message.putInt(123456789);
        new Handler().postDelayed(() -> getFlutterView().send(CHANNEL_BINARY,message), TIME_ONE_SECOND);
        getFlutterView().setMessageHandler(CHANNEL_BINARY, (byteBuffer, binaryReply) -> {
            byteBuffer.order(ByteOrder.nativeOrder());
            double x = byteBuffer.getDouble();
            int n = byteBuffer.getInt();
            Log.i("zj", "Received: "+x+ " and "+ n);
            binaryReply.reply(message);
        });
    }

Flutter中监听，发送

static const channel = const BasicMessageChannel<String>('com.jzhu.msg/plugin', StringCodec());

static const String channelBinary = 'com.jzhu.msg.binary/plugin';

void _sendMsg2Android() async {

     _replyMsg = await channel.send('TestPage：发条消息给你');
     setState(() {});

     final WriteBuffer buffer = WriteBuffer()
       ..putFloat64(3.14)
       ..putInt32(123456789);
     final ByteData message = buffer.done();
     _replyBinaryMsg = await BinaryMessages.send(channelBinary, message);
     _decodeData(message);

  }

  void _initMessageHandler() {

    channel.setMessageHandler((String message) async {
      _receivedMsg  = message;
      setState(() {});
      });

    BinaryMessages.setMessageHandler(channelBinary, (ByteData message) async {
      _decodeData(message);
    });

  }

  void _decodeData(ByteData message){
    final ReadBuffer readBuffer = ReadBuffer(message);
    final double x = readBuffer.getFloat64();
    final int n = readBuffer.getInt32();
    print('Received $x and $n');
  }

疑问：已有项目集成到Flutter，自定义插件应该放在哪注册，什么时机注册？有想法的私信留言谢谢！

已有项目集成到Flutter，后续遇到问题解决后会整理发布，或者你们觉得可能存在的问题，可以私信我，留言，空余时间会尽力尝试解决。

已有项目集成到Flutter代码已经上传到我的GITHUB

知乎日报Flutter版代码已经上传到我的GITHUB

基础学习过程中的代码都放在GITHUB

每天学一点，学到Flutter发布正式版！