flutter和android原生通信的理解(1)
flutter和android原生通信的理解(2)

Flutter层 的Plugin注册

创建 _channel对象

static const _channel = const MethodChannel('vn.hunghd/downloader');

class MethodChannel {
 //...
  const MethodChannel(this.name, [this.codec = const StandardMethodCodec(), BinaryMessenger binaryMessenger ])
      : assert(name != null),
        assert(codec != null),
        _binaryMessenger = binaryMessenger;

//..
 Future<T> _invokeMethod<T>(String method, { bool missingOk, dynamic arguments }) async {
   
    final ByteData result = await binaryMessenger.send(
      name,
      codec.encodeMethodCall(MethodCall(method, arguments)),
    );
    if (result == null) {
      if (missingOk) {
        return null;
      }
      throw MissingPluginException('No implementation found for method $method on channel $name');
    }
    return codec.decodeEnvelope(result) as T;
  }

MethodChannel 的构造方法中

• 传入 通道名字
• 获取一个BinaryMessenger binaryMessenger 对象;
  binaryMessenger 用来发送消息的接口，只不过是 Flutter层的；

binaryMessenger 对象，由ServicesBinding 在初始化时 创建

mixin ServicesBinding on BindingBase {
  @override
  void initInstances() {
    super.initInstances();
    _instance = this;
    _defaultBinaryMessenger = createBinaryMessenger();
    //...
  }

Flutter 中 BinaryMessenger是一个接口，实现类是_DefaultBinaryMessenger，
具体功能 是通过 Flutter中的 单例对象 window实现