在Flutter中从video_player插件中获取当前帧？

import 'package:video_player/video_player.dart';

VideoPlayerController _controller;

void initializeVideoPlayer() {
  _controller = VideoPlayerController.network('视频URL');
  _controller.initialize().then((_) {
    setState(() {});
  });
}

Image currentFrame = Image.memory(_controller.value.frame);

import 'package:flutter/material.dart';
import 'package:video_player/video_player.dart';

class VideoPlayerPage extends StatefulWidget {
  @override
  _VideoPlayerPageState createState() => _VideoPlayerPageState();
}

class _VideoPlayerPageState extends State<VideoPlayerPage> {
  VideoPlayerController _controller;

  @override
  void initState() {
    super.initState();
    initializeVideoPlayer();
  }

  void initializeVideoPlayer() {
    _controller = VideoPlayerController.network('视频URL');
    _controller.initialize().then((_) {
      setState(() {});
    });
  }

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

  @override
  Widget build(BuildContext context) {
    if (_controller.value.isInitialized) {
      return Scaffold(
        body: Center(
          child: Image.memory(_controller.value.frame),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            setState(() {
              _controller.value.isPlaying
                  ? _controller.pause()
                  : _controller.play();
            });
          },
          child: Icon(
            _controller.value.isPlaying ? Icons.pause : Icons.play_arrow,
          ),
        ),
      );
    } else {
      return Scaffold(
        body: Center(
          child: CircularProgressIndicator(),
        ),
      );
    }
  }
}