Flutter与原生交互使用Platform Channel。Flutter定义了三种不同类型的Channel，它们分别是： :::info BasicMessageChannel：用于传递字符串和半机构化的信息（双向有返回值） ::: :::warning MethodChannel：用于传递方法调用（双向有返回值） :::

EventChannel：用于数据流（event streams）的通信（仅支持数据单向传递，无返回值）

三种Channel之间相互独立、各有用途，但是在设计上非常相近。每种Channel均有三个变量： :::warning name：String类型，代表Channel的名字，也是其唯一标识符
messager：BinaryMessager类型，代表消息信使，是消息的发送与接收的工具
codec：MessageCodec类型或MethodCodec类型，代表消息的编解码器 :::

MethodChannel

1、Flutter跳转到原生且携带参数

实现插件

  1. public class FlutterPluginJumpToAct implements MethodChannel.MethodCallHandler {
  3.     public static String CHANNEL = "com.jzhu.jump/plugin";
  5.     static MethodChannel channel;
  7.     private Activity activity;
  9.     private FlutterPluginJumpToAct(Activity activity) {
  10.         this.activity = activity;
  11.     }
  13.     public static void registerWith(PluginRegistry.Registrar registrar) {
  14.         channel = new MethodChannel(registrar.messenger(), CHANNEL);
  15.         FlutterPluginJumpToAct instance = new FlutterPluginJumpToAct(registrar.activity());
  16.         //setMethodCallHandler在此通道上接收方法调用的回调
  17.         channel.setMethodCallHandler(instance);
  18.     }
  20.     @Override
  21.     public void onMethodCall(MethodCall call, MethodChannel.Result result) {
  23.         //通过MethodCall可以获取参数和方法名，然后再寻找对应的平台业务，本案例做了2个跳转的业务
  25.         //接收来自flutter的指令oneAct
  26.         if (call.method.equals("oneAct")) {
  28.             //跳转到指定Activity
  29.             Intent intent = new Intent(activity, OneActivity.class);
  30.             activity.startActivity(intent);
  32.             //返回给flutter的参数
  33.             result.success("success");
  34.         }
  35.         //接收来自flutter的指令twoAct
  36.         else if (call.method.equals("twoAct")) {
  38.             //解析参数
  39.             String text = call.argument("flutter");
  41.             //带参数跳转到指定Activity
  42.             Intent intent = new Intent(activity, TwoActivity.class);
  43.             intent.putExtra(TwoActivity.VALUE, text);
  44.             activity.startActivity(intent);
  46.             //返回给flutter的参数
  47.             result.success("success");
  48.         }
  49.         else {
  50.             result.notImplemented();
  51.         }
  52.     }
  54. }

插件注册

需要在继承了FlutterActivity中的Activity中注册

  1. public class MainActivity extends FlutterActivity {
  2.   @Override
  3.   protected void onCreate(Bundle savedInstanceState) {
  4.       super.onCreate(savedInstanceState);
  5.       GeneratedPluginRegistrant.registerWith(this);
  6.       registerCustomPlugin(this);
  7.   }
  9.   private static void registerCustomPlugin(PluginRegistry registrar) {
  10.       FlutterPluginJumpToAct.registerWith(registrar.registrarFor(FlutterPluginJumpToAct.CHANNEL));
  11.       FlutterPluginCounter.registerWith(registrar.registrarFor(FlutterPluginCounter.CHANNEL));
  12.   }
  13. }

带参数跳转

  1. //获取到插件与原生的交互通道
  2. static const jumpPlugin = const MethodChannel('com.jzhu.jump/plugin');
  4. Future<Null> _jumpToNative() async {
  5.   String result = await jumpPlugin.invokeMethod('oneAct');
  6.   print(result);
  7. }
  9. Future<Null> _jumpToNativeWithValue() async {
  10.   Map<String, String> map = { "flutter": "这是一条来自flutter的参数" };
  11.   String result = await jumpPlugin.invokeMethod('twoAct', map);
  12.   print(result);
  13. }

2、原生发送参数给Flutter

实现插件

  1. public class FlutterPluginCounter implements EventChannel.StreamHandler {
  3.     public static String CHANNEL = "com.jzhu.counter/plugin";
  5.     static EventChannel channel;
  7.     private Activity activity;
  9.     private FlutterPluginCounter(Activity activity) {
  10.         this.activity = activity;
  11.     }
  13.     public static void registerWith(PluginRegistry.Registrar registrar) {
  14.         channel = new EventChannel(registrar.messenger(), CHANNEL);
  15.         FlutterPluginCounter instance = new FlutterPluginCounter(registrar.activity());
  16.         channel.setStreamHandler(instance);
  17.     }
  19.     @Override
  20.     public void onListen(Object o, final EventChannel.EventSink eventSink) {
  22.         Observable.interval(1000, TimeUnit.MILLISECONDS).subscribe(new Observer<Long>() {
  23.             @Override
  24.             public void onSubscribe(Disposable d) {
  26.             }
  28.             @Override
  29.             public void onNext(Long aLong) {
  30.                 eventSink.success(aLong.intValue());
  31.             }
  33.             @Override
  34.             public void onError(Throwable e) {
  35.                 eventSink.error("计时器异常", "异常", e.getMessage());
  36.             }
  38.             @Override
  39.             public void onComplete() {
  40.             }
  41.         });
  43.     }
  45.     @Override
  46.     public void onCancel(Object o) {
  47.         Log.i("FlutterPluginCounter", "FlutterPluginCounter:onCancel");
  48.     }
  50. }

Flutter接收原生发送的参数

  1.   static const counterPlugin = const EventChannel('com.jzhu.counter/plugin');
  3.   StreamSubscription _subscription = null;
  5.   var _count;
  7.   @override
  8.   void initState() {
  9.     super.initState();
  10.     //开启监听
  11.     if(_subscription == null){
  12.       _subscription =  counterPlugin.receiveBroadcastStream().listen(_onEvent,onError: _onError);
  13.     }
  14.   }
  16.   @override
  17.   void dispose() {
  18.     super.dispose();
  19.     //取消监听
  20.     if(_subscription != null){
  21.       _subscription.cancel();
  22.     }
  23.   }
  25.   void _onEvent(Object event) {
  26.     setState(() {
  27.       _count = event;
  28.       print("ChannelPage: $event");
  29.     });
  30.   }
  32.   void _onError(Object error) {
  33.     setState(() {
  34.       _count = "计时器异常";
  35.       print(error);
  36.     });
  37.   }

其他

Debug模式原生跳转到Flutter界面会出现白屏，Release包就不会出现这种情况