import com.google.android.exoplayer2.upstream.cache.LeastRecentlyUsedCacheEvictor; //导入依赖的package包/类
@Override
public void onCreate() {
    super.onCreate();

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_DEFAULT_CHANNEL_ID, getString(R.string.notification_channel_name), NotificationManagerCompat.IMPORTANCE_DEFAULT);
        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.createNotificationChannel(notificationChannel);

        AudioAttributes audioAttributes = new AudioAttributes.Builder()
                .setUsage(AudioAttributes.USAGE_MEDIA)
                .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                .build();
        audioFocusRequest = new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN)
                .setOnAudioFocusChangeListener(audioFocusChangeListener)
                .setAcceptsDelayedFocusGain(false)
                .setWillPauseWhenDucked(true)
                .setAudioAttributes(audioAttributes)
                .build();
    }

    audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);

    mediaSession = new MediaSessionCompat(this, "PlayerService");
    mediaSession.setFlags(MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS);
    mediaSession.setCallback(mediaSessionCallback);

    Context appContext = getApplicationContext();

    Intent activityIntent = new Intent(appContext, MainActivity.class);
    mediaSession.setSessionActivity(PendingIntent.getActivity(appContext, 0, activityIntent, 0));

    Intent mediaButtonIntent = new Intent(Intent.ACTION_MEDIA_BUTTON, null, appContext, MediaButtonReceiver.class);
    mediaSession.setMediaButtonReceiver(PendingIntent.getBroadcast(appContext, 0, mediaButtonIntent, 0));

    exoPlayer = ExoPlayerFactory.newSimpleInstance(new DefaultRenderersFactory(this), new DefaultTrackSelector(), new DefaultLoadControl());
    exoPlayer.addListener(exoPlayerListener);
    DataSource.Factory httpDataSourceFactory = new OkHttpDataSourceFactory(new OkHttpClient(), Util.getUserAgent(this, getString(R.string.app_name)), null);
    Cache cache = new SimpleCache(new File(this.getCacheDir().getAbsolutePath() + "/exoplayer"), new LeastRecentlyUsedCacheEvictor(1024 * 1024 * 100)); // 100 Mb max
    this.dataSourceFactory = new CacheDataSourceFactory(cache, httpDataSourceFactory, CacheDataSource.FLAG_BLOCK_ON_CACHE | CacheDataSource.FLAG_IGNORE_CACHE_ON_ERROR);
    this.extractorsFactory = new DefaultExtractorsFactory();
}
 

import com.google.android.exoplayer2.upstream.cache.LeastRecentlyUsedCacheEvictor; //导入依赖的package包/类
private void configureExoMedia() {
    // Registers the media sources to use the OkHttp client instead of the standard Apache one
    // Note: the OkHttpDataSourceFactory can be found in the ExoPlayer extension library `extension-okhttp`
    ExoMedia.setDataSourceFactoryProvider(new ExoMedia.DataSourceFactoryProvider() {
        @NonNull
        @Override
        public DataSource.Factory provide(@NonNull String userAgent, @Nullable TransferListener<? super DataSource> listener) {
            // Updates the network data source to use the OKHttp implementation
            DataSource.Factory upstreamFactory = new OkHttpDataSourceFactory(new OkHttpClient(), userAgent, listener);

            // Adds a cache around the upstreamFactory
            Cache cache = new SimpleCache(getCacheDir(), new LeastRecentlyUsedCacheEvictor(50 * 1024 * 1024));
            return new CacheDataSourceFactory(cache, upstreamFactory, CacheDataSource.FLAG_IGNORE_CACHE_ON_ERROR);
        }
    });
}
 

import com.google.android.exoplayer2.upstream.cache.LeastRecentlyUsedCacheEvictor; //导入依赖的package包/类
@Override
public DataSource createDataSource() {
    LeastRecentlyUsedCacheEvictor evictor = new LeastRecentlyUsedCacheEvictor(maxCacheSize);
    SimpleCache simpleCache =
            new SimpleCache(new File(context.getCacheDir(), "media"), evictor);
    return new CacheDataSource(simpleCache, defaultDatasourceFactory.createDataSource(),
            new FileDataSource(), new CacheDataSink(simpleCache, maxFileSize),
            CacheDataSource.FLAG_BLOCK_ON_CACHE | CacheDataSource.FLAG_IGNORE_CACHE_ON_ERROR,
            null);
}
 

import com.google.android.exoplayer2.upstream.cache.LeastRecentlyUsedCacheEvictor; //导入依赖的package包/类
/***
 * @param context 上下文
 * @param maxCacheSize 缓存大小
 * @param secretKey If not null, cache keys will be stored encrypted on filesystem using AES/CBC.     The key must be 16 bytes long.
 * @param listener the listener
 */
public DefaultCacheDataSourceFactory(@NonNull Context context, long maxCacheSize, byte[] secretKey, @Nullable CacheDataSource.EventListener listener) {
    defaultDatasourceFactory = new JDefaultDataSourceFactory(context);
    simpleCache = new SimpleCache(new File(context.getExternalCacheDir(), "media1"), new LeastRecentlyUsedCacheEvictor(maxCacheSize), secretKey);
    this.listener = listener;
}