floatingActionButton: FloatingActionButton(
    onPressed: () => controller.changeBackground('#FFFFFF'),
),

Future<void> changeBackground(String colorString) async {
    try {
     return _channel.invokeMethod('changeBackgroundColor', <String, dynamic> {
     'color': colorString
     });
    } catch (e) {
    }
}

- (void)onMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
    if ([call.method isEqualToString:@"changeBackgroundColor"]) {
        NSString *colorString = call.arguments[@"color"];
        if (colorString.length != 0) {
            _templcateView.backgroundColor = [UIColor colorWithHexString:colorString];
            result(@0);
            return;
        }
    }
    result(FlutterMethodNotImplemented);
}

思考题实现思路

dart层设置颜色参数的方法：
changeBackgroundColor(int r, int g, int b) async
  {
    _channel.invokeMethod('changeBackgroundColor', {"r":r, "g":g, "b":b});
  }

dart层调用：
controller.changeBackgroundColor(0, 255, 255)

android native层实现：
if (methodCall.method.equals("changeBackgroundColor")) {
      int r = methodCall.argument("r");
      int g = methodCall.argument("g");
      int b = methodCall.argument("b");
      view.setBackgroundColor(Color.rgb(r, g, b));
      result.success(0);
    }else {
      result.notImplemented();
    }

思考题如下：

//声明修改原生控件背景的方法
  changeBgColor() async {
    try {
      _methodChannel.invokeMethod("changeBgColor", {
        "color1": Random().nextInt(255),
        "color2": Random().nextInt(255),
        "color3": Random().nextInt(255)
      });
    } catch (e) {
      print(e);
    }
  }

override fun onMethodCall(p0: MethodCall, p1: MethodChannel.Result) {
            when (p0.method) {
                "changeBgColor" -> {
                    view.setBackgroundColor(Color.rgb(p0.argument<Int>("color1")!!, p0.argument<Int>("color2")!!, p0.argument<Int>("color3")!!))
                    p1.success(0)
                }
                //如果是别的方法则返回未实现
                else -> p1.notImplemented()
            }
        }