Android：媒体文件从文件系统中消失

Question

我遇到了一个奇怪的问题。我有一个 MediaPlayer 活动，应该播放刚刚录制的音频文件。首先媒体播放器初始化正常并且可以播放文件。

当我旋转屏幕时，活动会被破坏，然后重新初始化为新的方向。因此，我也重新初始化媒体播放器。

这可以工作几次，但在某些时候 mediaPlayer.setDataSource() 会抛出 NullPointerException，因为文件突然消失了。遗憾的是，我在日志中没有看到任何其他错误。

以下是一些代码片段：

播放器创建：

/**
 * Creates and initializes the player with the proper file.
 */
private void createPlayer() {
    synchronized (playerMutex) {
        player = new MediaPlayer();
        player.setLooping(false);
        player.setOnPreparedListener(this);
        player.setOnErrorListener(this);
        player.setOnCompletionListener(this);
    }
    readGreeting();
}

播放器初始化：

    isPrepared = false;
    try {
        final File file = new File(audioFilename);

        in = new FileInputStream(file);
        synchronized (playerMutex) {
            player.setDataSource(in.getFD());
        }

        // using a runnable instead of prepareAsync to not accidentally call pause on media player while preparing
        Runnable preparer = new Runnable() {
            @Override
            public void run() {
                try {
                    synchronized (playerMutex) {
                        if (player != null) {
                            player.prepare();
                        }
                    }
                } catch (Exception ex) {
                    Log.e(TAG, "Error preparing player for file " + file.getAbsolutePath(), ex);
                }
            }
        };
        new Thread(preparer).start();
    } catch (Exception ex) {
        btnPlayback.setEnabled(false);
        Log.e(TAG, "Error preparing player", ex);
    } finally {
        if (in != null) {
            try {
                in.close();
            } catch (IOException e) {
                Log.e(TAG, "initPlayer: ", e);
            }
        }
    }

保存实例状态...

@Override
protected void onPause() {
    synchronized (playerMutex) {

        if (isPlaying()) {
            getIntent().putExtra(EXTRA_KEY_SEEK, player.getCurrentPosition());
            pause();
        }
    }
    setAudioModeBackToNormal();
    super.onPause();
}

private void pause() {
    synchronized (playerMutex) {
        if (isPlaying()) {
            player.pause();
        }
    }
    btnPlayback.setVisibility(View.VISIBLE);
    btnPause.setVisibility(View.GONE);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    final Bundle extras = getIntent().getExtras();

    outState.putBundle("extras", extras);
    super.onSaveInstanceState(outState);
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    getIntent().putExtras(savedInstanceState.getBundle("extras"));
}

清理：

private void stopPlayerAndFreeResources() {
    synchronized (playerMutex) {
        isPrepared = false;
        if (player != null) {
            player.stop();
            player.release();
            player = null;
        }
    }
    if (in != null) {
        try {
            in.close();
            in = null;
        } catch (IOException e) {
             Log.e(TAG, "Unexpected error", e);
        }
    }
}

也许我从错误的角度看待问题，它与播放器无关。有人遇到过文件消失的问题吗？

Answer 1

我有一次播放列表文件消失了。问题的原因是某些媒体播放器可以选择管理我的播放列表。在这种情况下，管理意味着删除我已有的播放列表:(