从视频文件创建缩略图返回空位图

我发送启动摄像机的意图

PackageManager pm = getPackageManager();
    if(pm.hasSystemFeature(PackageManager.FEATURE_CAMERA)){
            Intent video = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
            File tempDir= new File(Environment.getExternalStoragePublicDirectory(
                      Environment.DIRECTORY_PICTURES), "BCA");
            if(!tempDir.exists())
            {
                if(!tempDir.mkdir()){
                    Toast.makeText(this, "Please check SD card! Image shot is impossible!", Toast.LENGTH_SHORT).show();
                }
            }

                String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",Locale.US).format(new Date());
                File mediaFile = new File(tempDir.getPath() + File.separator +
                "VIDEO_"+ timeStamp + ".mp4");
                Uri videoUri = Uri.fromFile(mediaFile);
                video.putExtra(MediaStore.EXTRA_OUTPUT, videoUri);
                video.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);
                startActivityForResult(video, VIDEO_REQUEST);

    }else{
        Toast.makeText(this, "This device does not have a rear facing camera",Toast.LENGTH_SHORT).show();
    }

我拍摄了一段视频并正确存储，当onActivityResult被解雇 我用意图来获得uri用于创建位图的存储位置

这是 uri 的示例file:///storage/emulated/0/Pictures/BCA/VIDEO_20131227_145043.mp4

 Bitmap bitmap = ThumbnailUtils.createVideoThumbnail(intent.getDataString(), MediaStore.Video.Thumbnails.MICRO_KIND);

但位图每次都是空的。所以既然文档说May return null if the video is corrupt or the format is not supported我检查了目录中的视频，它播放得很好，而且它的.mp4文件受支持，那么我在这里做错了什么？

你可以试试媒体元数据检索器 http://developer.android.com/reference/android/media/MediaMetadataRetriever.html or FFmpeg媒体元数据检索器 https://github.com/wseemann/FFmpegMediaMetadataRetriever。这是一个例子：

FFmpegMediaMetadataRetriever mmr = new FFmpegMediaMetadataRetriever();
mmr.setDataSource(intent.getDataString());
Bitmap b = mmr.getFrameAtTime();
mmr.release();