dispose method
关闭并销毁消息通道 Close and destroy the message channel
Implementation
Future<bool> dispose() async {
assert(_channel != null, 'You must call setMethodChannel() first');
if (!_supportPlatform || _channel == null) return false;
await _streamSubscription?.cancel();
_streamSubscription = null;
_stream = null;
_eventChannel = null;
final bool? state = await _channel!.invokeMethod<bool>('stopEvent');
return state ?? false;
}