flutter开发实战-实现获取视频的缩略图封面video_thumbnail

在很多时候，我们查看视频的时候，视频没有播放时候，会显示一张封面，可能封面没有配置图片，这时候就需要通过获取视频的缩略图来显示封面了。这里使用了video_thumbnail来实现获取视频的缩略图。

一、引入video_thumbnail

在工程的pubspec.yaml中引入插件

  # 视频缩略图
  video_thumbnail: ^0.5.3
    

VideoThumbnail的属性如下

static Future<String?> thumbnailFile(
      {required String video,
      Map<String, String>? headers,
      String? thumbnailPath,
      ImageFormat imageFormat = ImageFormat.PNG,
      int maxHeight = 0,
      int maxWidth = 0,
      int timeMs = 0,
      int quality = 10}) 
    

• thumbnailPath为本地存储的文件目录
• imageFormat格式 jpg，png等
• video视频地址
• timeMs

二、获取视频的缩略图

使用video_thumbnail来获取视频缩略图

定义视频缩略图信息

class VideoThumbInfo {
  String url; // 原视频地址
  File? thumbFile; // 缩略图本地file
  int? width; // 缩略图的width
  int? height; // 缩略图的height

  VideoThumbInfo({
    required this.url,
  });
}
    

获取视频缩略图本地File

String path = (await getTemporaryDirectory()).path;
    String thumbnailPath = path + "/${DateTime.now().millisecond}.jpg";
    final fileName = await VideoThumbnail.thumbnailFile(
      video:
          "https://vd2.bdstatic.com/mda-maif0tt1rirqp27q/540p/h264_cae/1611052585/mda-maif0tt1rirqp27q.mp4",
      thumbnailPath: thumbnailPath,
      imageFormat: imageFormat,
      quality: quality,
      maxWidth: maxWidth,
      maxHeight: maxHeight,
      timeMs: timeMs,
    );

    File file = File(thumbnailPath);
    

获取缩略图的宽高

Image image = Image.file(thumbFile!);
      image.image.resolve(const ImageConfiguration()).addListener(
            ImageStreamListener(
              (ImageInfo imageInfo, bool synchronousCall) {
                int imageWidth = imageInfo.image.width;
                int imageHeight = imageInfo.image.height;
                VideoThumbInfo videoThumbInfo = VideoThumbInfo(url: url);
                videoThumbInfo.thumbFile = thumbFile;
                videoThumbInfo.width = imageWidth;
                videoThumbInfo.height = imageHeight;
                VideoThumb.setThumbInfo(url, videoThumbInfo);
                onVideoThumbInfoListener(videoThumbInfo);
              },
              onError: (exception, stackTrace) {
                print(
                    "getVideoThumbInfoByFile imageStreamListener onError exception:${exception.toString()},stackTrace:${stackTrace}");
                onVideoThumbInfoListener(null);
              },
            ),
          );
    

完整代码如下

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:video_thumbnail/video_thumbnail.dart';

// ignore: non_constant_identifier_names
VideoThumbManager get VideoThumb => VideoThumbManager.instance;

class VideoThumbManager {
  static VideoThumbManager get instance {
    return _singleton;
  }

  //保存单例
  static VideoThumbManager _singleton = VideoThumbManager._internal();

  //工厂构造函数
  factory VideoThumbManager() => _singleton;

  //私有构造函数
  VideoThumbManager._internal();

  // 保存url对应的本地缩略图file
  final _thumbMap = Map<String, File>();

  // url对应本地缩略图的信息
  final _thumbInfoMap = Map<String, VideoThumbInfo>();

  Future<void> setThumb(String url, File file) async {
    if (url.isEmpty) {
      return;
    }

    bool exist = await file.exists();
    if (exist == false) {
      return;
    }

    _thumbMap[url] = file;
  }

  Future<File?> getThumb(
    String url, {
    ImageFormat imageFormat = ImageFormat.JPEG,
    int maxHeight = 0,
    int maxWidth = 0,
    int timeMs = 0,
    int quality = 100,
  }) async {
    File? thumbFile = _thumbMap[url];
    if (thumbFile != null) {
      return thumbFile;
    }

    String path = (await getTemporaryDirectory()).path;
    String thumbnailPath = path + "/${DateTime.now().millisecond}.jpg";
    final fileName = await VideoThumbnail.thumbnailFile(
      video:
          "https://vd2.bdstatic.com/mda-maif0tt1rirqp27q/540p/h264_cae/1611052585/mda-maif0tt1rirqp27q.mp4",
      thumbnailPath: thumbnailPath,
      imageFormat: imageFormat,
      quality: quality,
      maxWidth: maxWidth,
      maxHeight: maxHeight,
      timeMs: timeMs,
    );

    File file = File(thumbnailPath);
    setThumb(url, file);
    return file;
  }

  // 获取缩略图的大小
  void getVideoThumbInfo(
    String url, {
    ImageFormat imageFormat = ImageFormat.JPEG,
    int maxHeight = 0,
    int maxWidth = 0,
    int timeMs = 0,
    int quality = 100,
    required Function(VideoThumbInfo?) onVideoThumbInfoListener,
  }) async {
    try {
      VideoThumbInfo? thumbInfo = VideoThumb.getThumbInfo(url);
      if (thumbInfo != null) {
        onVideoThumbInfoListener(thumbInfo);
        return;
      }

      await VideoThumb.getThumb(
        url,
        imageFormat: imageFormat,
        maxWidth: maxWidth,
        maxHeight: maxHeight,
        timeMs: timeMs,
        quality: quality,
      ).then((value) {
        File? thumbFile = value;
        if (thumbFile != null) {
          VideoThumb.getVideoThumbInfoByFile(
            url: url,
            thumbFile: thumbFile,
            onVideoThumbInfoListener: onVideoThumbInfoListener,
          );
        } else {
          onVideoThumbInfoListener(null);
        }
      }).onError((error, stackTrace) {
        print("getVideoThumbInfo error:${error.toString()}");
        onVideoThumbInfoListener(null);
      }).whenComplete(() {
        print("getVideoThumbInfo whenComplete");
      });
    } catch (e) {
      print("getVideoThumbInfo catch error:${e.toString()}");
      onVideoThumbInfoListener(null);
    }
  }

  /// 根据file获取缩略图信息
  void getVideoThumbInfoByFile({
    required String url,
    required File thumbFile,
    required Function(VideoThumbInfo?) onVideoThumbInfoListener,
  }) async {
    try {
      VideoThumbInfo? thumbInfo = VideoThumb.getThumbInfo(url);
      if (thumbInfo != null) {
        onVideoThumbInfoListener(thumbInfo);
        return;
      }

      Image image = Image.file(thumbFile!);
      image.image.resolve(const ImageConfiguration()).addListener(
            ImageStreamListener(
              (ImageInfo imageInfo, bool synchronousCall) {
                int imageWidth = imageInfo.image.width;
                int imageHeight = imageInfo.image.height;
                VideoThumbInfo videoThumbInfo = VideoThumbInfo(url: url);
                videoThumbInfo.thumbFile = thumbFile;
                videoThumbInfo.width = imageWidth;
                videoThumbInfo.height = imageHeight;
                VideoThumb.setThumbInfo(url, videoThumbInfo);
                onVideoThumbInfoListener(videoThumbInfo);
              },
              onError: (exception, stackTrace) {
                print(
                    "getVideoThumbInfoByFile imageStreamListener onError exception:${exception.toString()},stackTrace:${stackTrace}");
                onVideoThumbInfoListener(null);
              },
            ),
          );
    } catch (e) {
      print("getVideoThumbInfoByFile catch error:${e.toString()}");
      onVideoThumbInfoListener(null);
    }
  }

  void removeThumb(String url) {
    if (url.isEmpty) {
      return;
    }

    _thumbMap.remove(url);
  }

  /// 获取存储缩略图信息
  VideoThumbInfo? getThumbInfo(String url) {
    if (url.isEmpty) {
      return null;
    }

    VideoThumbInfo? thumbInfo = _thumbInfoMap[url];
    return thumbInfo;
  }

  /// 存储缩略图信息
  void setThumbInfo(String url, VideoThumbInfo videoThumbInfo) async {
    if (url.isEmpty) {
      return;
    }

    _thumbInfoMap[url] = videoThumbInfo;
  }

  void removeThumbInfo(String url) {
    if (url.isEmpty) {
      return;
    }

    _thumbInfoMap.remove(url);
  }

  void clear() {
    _thumbMap.clear();
    _thumbInfoMap.clear();
  }
}

class VideoThumbInfo {
  String url; // 原视频地址
  File? thumbFile; // 缩略图本地file
  int? width; // 缩略图的width
  int? height; // 缩略图的height

  VideoThumbInfo({
    required this.url,
  });
}

    

三、显示视频缩略图的Widget

用于显示视频缩略图的Widget

/// 用于显示视频缩略图的Widget
class VideoThumbImage extends StatefulWidget {
  const VideoThumbImage(
      {super.key, required this.url, this.maxWidth, this.maxHeight});

  final String url;
  final double? maxWidth;
  final double? maxHeight;

  @override
  State<VideoThumbImage> createState() => _VideoThumbImageState();
}

class _VideoThumbImageState extends State<VideoThumbImage> {
  VideoThumbInfo? _videoThumbInfo;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    VideoThumb.getVideoThumbInfo(widget.url,
        onVideoThumbInfoListener: (VideoThumbInfo? thumbInfo) {
      if (mounted) {
        setState(() {
          _videoThumbInfo = thumbInfo;
        });
      }
    });
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
  }

  // 根据VideoThumb来显示图片
  Widget buildVideoThumb(BuildContext context) {
    if (_videoThumbInfo != null && _videoThumbInfo!.thumbFile != null) {
      double? imageWidth;
      double? imageHeight;
      if (_videoThumbInfo!.width != null && _videoThumbInfo!.height != null) {
        imageWidth = _videoThumbInfo!.width!.toDouble();
        imageWidth = _videoThumbInfo!.height!.toDouble();
      }

      return Container(
        width: imageWidth,
        height: imageHeight,
        clipBehavior: Clip.hardEdge,
        decoration: const BoxDecoration(
          color: Colors.transparent,
        ),
        child: Image.file(
          _videoThumbInfo!.thumbFile!,
          width: imageWidth,
          height: imageHeight,
        ),
      );
    }

    return Container();
  }

  @override
  Widget build(BuildContext context) {
    return ConstrainedBox(
      constraints: BoxConstraints(
        maxWidth: widget.maxWidth ?? double.infinity,
        maxHeight: widget.maxHeight ?? double.infinity,
      ),
      child: buildVideoThumb(context),
    );
  }
}

    

效果图如下：

四、小结

flutter开发实战-实现获取视频的缩略图封面video_thumbnail

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