setWatermarkVisible method
设置水印显示和隐藏
visable true:显示水印,false:隐藏水印
Implementation
Future<void> setWatermarkVisible(bool visable) async {
  return AlivcLivePusher.methodChannel.invokeMethod(
      'setWatermarkVisible', _wrap(arg: AlivcLiveTool.boolToString(visable)));
}