dispose method

@override Future<void> dispose()

视频销毁，在dispose后，应当释放任何内存资源

Implementation

@override
Future<void> dispose() async {
  if (!prepared) return;
  _prepared = false;
  await _syncCall(() async {
    await this.controller.dispose();
    _controller = null;
    _disposeLock = Completer<void>();
  });
}