Flutter知识点: Flutter与原生(Android)的交互

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2018-08-07
原文链接:www.jianshu.com

Flutter与原生的交互主要通过MethodChannel的方式

效果GIF

Channel.gif

从Flutter界面跳转到原生,且带参数

1. 实现插件

public class FlutterPluginJumpToAct implements MethodChannel.MethodCallHandler {

  public static String CHANNEL = "com.jzhu.jump/plugin";

  static MethodChannel channel;

  private Activity activity;

  private FlutterPluginJumpToAct(Activity activity) {
      this.activity = activity;
  }

  public static void registerWith(PluginRegistry.Registrar registrar) {
      channel = new MethodChannel(registrar.messenger(), CHANNEL);
      FlutterPluginJumpToAct instance = new FlutterPluginJumpToAct(registrar.activity());
      //setMethodCallHandler在此通道上接收方法调用的回调
      channel.setMethodCallHandler(instance);
  }

  @Override
  public void onMethodCall(MethodCall call, MethodChannel.Result result) {

      //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

      //接收来自flutter的指令oneAct
      if (call.method.equals("oneAct")) {

          //跳转到指定Activity
          Intent intent = new Intent(activity, OneActivity.class);
          activity.startActivity(intent);

          //返回给flutter的参数
          result.success("success");
      }
      //接收来自flutter的指令twoAct
      else if (call.method.equals("twoAct")) {

          //解析参数
          String text = call.argument("flutter");

          //带参数跳转到指定Activity
          Intent intent = new Intent(activity, TwoActivity.class);
          intent.putExtra(TwoActivity.VALUE, text);
          activity.startActivity(intent);

          //返回给flutter的参数
          result.success("success");
      }
      else {
          result.notImplemented();
      }
  }

}

2. 插件注册

需要在继承了FlutterActivity中的Activity注册

public class MainActivity extends FlutterActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      GeneratedPluginRegistrant.registerWith(this);
      registerCustomPlugin(this);
  }

  private static void registerCustomPlugin(PluginRegistry registrar) {

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

      FlutterPluginCounter.registerWith(registrar.registrarFor(FlutterPluginCounter.CHANNEL));
  }


}

3. 带参数跳转

//获取到插件与原生的交互通道
static const jumpPlugin = const MethodChannel('com.jzhu.jump/plugin');

Future<Null> _jumpToNative() async {
  String result = await jumpPlugin.invokeMethod('oneAct');

  print(result);
}

Future<Null> _jumpToNativeWithValue() async {

  Map<String, String> map = { "flutter": "这是一条来自flutter的参数" };

  String result = await jumpPlugin.invokeMethod('twoAct', map);

  print(result);
}

参数解释

1. 传递的参数

参数可以不指定类型

Future<dynamic> invokeMethod(String method, [dynamic arguments]) async {
  assert(method != null);
  final dynamic result = await BinaryMessages.send(
    name,
    codec.encodeMethodCall(new MethodCall(method, arguments)),
  );
  if (result == null)
    throw new MissingPluginException('No implementation found for method $method on channel $name');
  return codec.decodeEnvelope(result);
}

2. 解析传递的参数

解析的参数是泛型

  public <T> T arguments() {
      return this.arguments;
  }

  public <T> T argument(String key) {
      if (this.arguments == null) {
          return null;
      } else if (this.arguments instanceof Map) {
          return ((Map)this.arguments).get(key);
      } else if (this.arguments instanceof JSONObject) {
          return ((JSONObject)this.arguments).opt(key);
      } else {
          throw new ClassCastException();
      }
  }

原生主动发送参数给Flutter

1. 实现插件

public class FlutterPluginCounter implements EventChannel.StreamHandler {

  public static String CHANNEL = "com.jzhu.counter/plugin";

  static EventChannel channel;

  private Activity activity;

  private FlutterPluginCounter(Activity activity) {
      this.activity = activity;
  }

  public static void registerWith(PluginRegistry.Registrar registrar) {
      channel = new EventChannel(registrar.messenger(), CHANNEL);
      FlutterPluginCounter instance = new FlutterPluginCounter(registrar.activity());
      channel.setStreamHandler(instance);
  }

  @Override
  public void onListen(Object o, final EventChannel.EventSink eventSink) {

      Observable.interval(1000, TimeUnit.MILLISECONDS).subscribe(new Observer<Long>() {
          @Override
          public void onSubscribe(Disposable d) {

          }

          @Override
          public void onNext(Long aLong) {
              eventSink.success(aLong.intValue());
          }

          @Override
          public void onError(Throwable e) {
              eventSink.error("计时器异常", "异常", e.getMessage());
          }

          @Override
          public void onComplete() {
          }
      });

  }

  @Override
  public void onCancel(Object o) {
      Log.i("FlutterPluginCounter", "FlutterPluginCounter:onCancel");
  }

}

2. Flutter接收原生发送的参数

  static const counterPlugin = const EventChannel('com.jzhu.counter/plugin');

  StreamSubscription _subscription = null;

  var _count;

  @override
  void initState() {
    super.initState();
    //开启监听
    if(_subscription == null){
      _subscription =  counterPlugin.receiveBroadcastStream().listen(_onEvent,onError: _onError);
    }
  }

  @override
  void dispose() {
    super.dispose();
    //取消监听
    if(_subscription != null){
      _subscription.cancel();
    }
  }

  void _onEvent(Object event) {
    setState(() {
      _count = event;
      print("ChannelPage: $event");
    });
  }

  void _onError(Object error) {
    setState(() {
      _count = "计时器异常";
      print(error);
    });
  }


暂未解决的问题 : 原生跳转到flutter界面会出现白屏

知乎日报Flutter版代码已经上传到我的GITHUB ZhihuDailyPurifyByFlutter

基础学习过程中的代码都放在GITHUB Flutter_Study

每天学一点,学到Flutter发布正式版!

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