如何在flutter中更改视频中的位置？

import 'package:video_player/video_player.dart';
import 'package:chewie/chewie.dart';

VideoPlayerController _controller;

@override
void initState() {
  super.initState();
  _controller = VideoPlayerController.asset('assets/video/video.mp4');
  _controller.initialize().then((_) {
    setState(() {});
  });
}

@override
void dispose() {
  super.dispose();
  _controller.dispose();
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text('Video Player'),
    ),
    body: _controller.value.isInitialized
        ? Chewie(
            controller: ChewieController(
              videoPlayerController: _controller,
              autoPlay: true,
              looping: true,
            ),
          )
        : Container(),
  );
}