ExoPlayer + 边缓存边播放

在此基础上改动：https://www.cnblogs.com/candyzhmm/p/9957928.html

private void openPlayer(String videoUrl) {
    //创建播放器
    player = ExoPlayerFactory.newSimpleInstance(this, trackSelector);

    //创建加载数据的工厂
    DataSource.Factory dataSourceFactory = new DefaultDataSourceFactory(this,
            Util.getUserAgent(this, BuildConfig.APPLICATION_ID), (TransferListener<? super DataSource>) bandwidthMeter);

    CacheDataSourceFactory videoDataSourceFactory = null;
    Cache cache = VideoCache.getInstance();
    long dataSize = FileUtils.getDirLength(CACHE_VIDEO_PATH);
    if (dataSize < Constants.CACHE_VIDEO_SIZE) {
        // CacheDataSinkFactory 第二个参数为单个缓存文件大小，如果需要缓存的文件大小超过此限制，则会分片缓存，不影响播放
        DataSink.Factory cacheWriteDataSinkFactory = new CacheDataSinkFactory(cache, Long.MAX_VALUE);
        videoDataSourceFactory = new CacheDataSourceFactory(cache, dataSourceFactory, new FileDataSourceFactory(), cacheWriteDataSinkFactory, CacheDataSource.FLAG_BLOCK_ON_CACHE | CacheDataSource.FLAG_IGNORE_CACHE_ON_ERROR, null);
    }

    Uri videoUri = null;
    try {
        videoUri = Uri.parse(videoUrl);
    } catch (Exception e) {
        return;
    }
    MediaSource videoSource = null;
    if (videoDataSourceFactory == null) {
        videoSource = new ExtractorMediaSource.Factory(dataSourceFactory).createMediaSource(videoUri);
    } else {
        videoSource = new ExtractorMediaSource.Factory(videoDataSourceFactory).createMediaSource(videoUri);
    }
    //循环播放
    LoopingMediaSource loopingMediaSource = new LoopingMediaSource(videoSource);
    player.prepare(loopingMediaSource);
    player.addListener(eventListener);
    player.setPlayWhenReady(true);
}

public class VideoCache {

    private static SimpleCache sDownloadCache;

    public static SimpleCache getInstance() {
        if (sDownloadCache == null)
            sDownloadCache = new SimpleCache(createFile(Constants.CACHE_VIDEO_PATH), new NoOpCacheEvictor());
        return sDownloadCache;
    }

    private static File createFile(String path) {
        File file = new File(path);
        //判断文件目录是否存在
        if (!file.exists()) {
            file.mkdirs();
        }
        return file;
    }
}

还有另外一种实现视频缓存方式：

AndroidVideoCache  参考：https://www.jianshu.com/p/53c4a6c9bd07

github地址： https://github.com/danikula/AndroidVideoCache