flutter 与原生的通信(Android 视角)

Flutter 提供 MethodChannel、EventChannel、BasicMessageChannel 三种方式

flutter 与原生的通信

MethodChannel

由 flutter 发起作为 client 方,native 接收作为 server 方,并能进行消息回传

• flutter:

class FlutterPlugin {
  ///指定channel名称
  static const MethodChannel _channel = const MethodChannel('flutter_plugin');

  ///发送消息
  static Future<String> showToast({String msg}) async {
    String result = await _channel.invokeMethod('toast',{"msg":msg});
    return result;
  }
}

1.渠道名: flutter_plugin
2.方法名: toast
3.参数: {"msg":msg}  参数必须以键值对的方式发送
4.result结果,原生回传消息

发送方参数一定要是键值对

• 原生:

public class FlutterPlugin implements MethodCallHandler {
    /**
     * Plugin registration.
     */
    public static void registerWith(Registrar registrar) {
        //1.通道名
        MethodChannel channel = new MethodChannel(registrar.messenger(), "flutter_plugin");
        channel.setMethodCallHandler(new FlutterPlugin());
    }

    @Override
    public void onMethodCall(MethodCall call, Result result) {
        String method = call.method;
        //2.对应方法名
        switch (method) {
            case "getPlatformVersion":
                result.success("Android " + android.os.Build.VERSION.RELEASE);
                break;
            case "toast":
                //3.参数名
                String msg = call.argument("msg");
                Toast.makeText(FlutterAAR.getApp(), msg, Toast.LENGTH_SHORT).show();
                //4.返回值
                result.success("成功啦");
                break;
            default:
                result.notImplemented();
                break;
        }
    }
}

每回通讯,需协商好这四个位置,需要一一对应

• 注意

本次通讯的方式并没有使用插件,因此GeneratedPluginRegistrant中并不会自动生成对于这个通讯通道的注册,需要自己手动注册,又因为GeneratedPluginRegistrant会每次自动生成,因此,更改GeneratedPluginRegistrant是没有效果的

public class MyGeneratedPluginRegistrant {
    public MyGeneratedPluginRegistrant() {
    }

    public static void registerWith(PluginRegistry registry) {
        GeneratedPluginRegistrant.registerWith(registry);
        FlutterPlugin.registerWith(registry.registrarFor("io.flutter.plugins.FlutterPlugin"));
    }
}

原生与 flutter 的通信

EventChannel

• flutter

  ///接收消息 1. 渠道: flutter_receive
  static const EventChannel _receiver_channel =
      const EventChannel('flutter_receive');

  ///2. 注册接收消息
  static void registerReceive(void onData(T),
      {bool cancelOnError, void onDone(), Function onError}) {
    _receiver_channel.receiveBroadcastStream().listen(
        (data) {
          if (onData != null) {
            onData(data);
          }
        },
        cancelOnError: cancelOnError,
        onDone: () {
          if (onDone != null) {
            onDone();
          }
        },
        onError: (error) {
          if (onError != null) {
            onError(error);
          }
        });
  }

  //使用
  @override
  void initState() {
    super.initState();
    FlutterPlugin.registerReceive(
        (data) {
          final Map<dynamic, dynamic> map = data;
          print(map['receive']);
        },
        cancelOnError: true,
        onDone: () {
          print('complete');
        },
        onError: (error) {
          if (error is PlatformException) {
            print(error.message);
          }
        });
  }

onDone和onError*(error)只会任选其一,走了onError*(error),则不会走onDone了

• 原生

public static void registerWith(Registrar registrar) {
  //创建原生接收通道
  MethodChannel channel = new MethodChannel(registrar.messenger(), "flutter_send");
  //选择通过构造方法的方式,创建原生发送通道
  channel.setMethodCallHandler(new FlutterPlugin(registrar));
}

 private FlutterPlugin(Registrar registrar){
    //1.渠道名
    EventChannel eventChannel = new EventChannel(registrar.messenger(),"flutter_receive");
    EventChannel.StreamHandler streamHandler = new EventChannel.StreamHandler() {
       @Override
       public void onListen(Object o, EventChannel.EventSink sink) {
          //2.发射器
          eventSink = sink;
       }

       @Override
       public void onCancel(Object o) {
           eventSink = null;
        }
      };
      eventChannel.setStreamHandler(streamHandler);
}

使用:
HashMap<String, String> hashMap = new HashMap<>(1);
hashMap.put("receive","abc");
eventSink.success(hashMap);
eventSink.error("其实没有错误","其实没有错误2","其实");
eventSink.endOfStream();

发送方参数一定要是键值对