当从扩展文件中读取mp3文件时,getFileDescriptor返回null

我已经下载并存储扩展文件successfully.But崩溃时,我尝试播放MP3里面..

ZipResourceFile expansionFile = APKExpansionSupport.getAPKExpansionZipFile(getApplicationContext(), 1, 0); InputStream fileStream = expansionFile.getInputStream("mysong.mp3"); AssetFileDescriptor asd = expansionFile.getAssetFileDescriptor("mysong.mp3"); MediaPlayer mediaPlayer = new MediaPlayer(); mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC); mediaPlayer.setDataSource(asd.getFileDescriptor(), asd.getStartOffset(), asd.getLength()); asd.close(); mediaPlayer.prepare(); mediaPlayer.start(); 

这里logcat说inputstream和文件描述符都是空的。任何人都可以帮我吗?

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