应用程序即使在删除后也会显示文件

Question

即使添加或删除了音乐文件，它也不会自动更新。它显示了所有缓存的文件。 虽然我已经使用了内容观察器，只有在完成复制或移动等操作时才更新它，我想在添加或删除新文件后立即更新活动。

public class MusicLoader extends AsyncTaskLoader<List<Music>> {

List<Music> mCache;
MusicObserver mMusicObserver;

public MusicLoader(Context context) {
    super(context);
}
@Override
public List<Music> loadInBackground() {

    final ContentResolver contentResolver = getContext().getContentResolver();
    String path = Environment.getExternalStorageDirectory().getAbsolutePath();

    String selection = String.format("%s !=%d AND %s LIKE '%s/Voico/%%'", MediaStore.Audio.Media.IS_MUSIC, 0, MediaStore.Audio.Media.DATA, path);

    String [] projections = {MediaStore.Audio.Media._ID,MediaStore.Audio.Media.DATA, MediaStore.Audio.Media.TITLE,MediaStore.Audio.Media.ARTIST, MediaStore.Audio.Media.ALBUM_ID};


    String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";
    Cursor cr = contentResolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,projections, selection, null, sortOrder);
    List<Music> items = new ArrayList<>();
    if(cr != null && cr.moveToFirst()) {
        // Cache the column indexes so we don't have to look them up for every iteration of the do-while loop.
        int idIndex = cr.getColumnIndex(MediaStore.Audio.Media._ID);
        int titleIndex = cr.getColumnIndex(MediaStore.Audio.Media.TITLE);
        int artistIndex = cr.getColumnIndex(MediaStore.Audio.Media.ARTIST);
        int albumId =  cr.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID);
        do {
            if(isLoadInBackgroundCanceled()){
                return items;
            }
            // Music object to hold the music data.
            Music item = new Music();
            // Retrieve the respective music data from the cursor using the column index.
            item.setId(cr.getLong(idIndex));
            item.setTitle(cr.getString(titleIndex));
            item.setArtist(cr.getString(artistIndex));
            item.setAlbumId(cr.getLong(albumId));
            // Once we've loaded the Music object, store it inside of the arraylist.
            items.add(item);
        }
        while(cr.moveToNext());
        cr.close();

    }
    return items;
}

@Override
public void deliverResult(List<Music> data) {
    if(isReset()){

        // CLose cursors or databse handles.
        return;
    }
    // Keep a reference to the loaded music data.
    mCache = data;

    // If we are started pass the loaded music to our super implementation that handles sending it to the registered activity/fragment.
    if(isStarted()){
        super.deliverResult(data);
    }
}

@Override
protected void onStopLoading() {
    cancelLoad();
}

@Override
protected void onStartLoading() {

    if(mCache != null) {
        deliverResult(mCache);

    }

    if(mMusicObserver == null) {
        mMusicObserver = new MusicObserver(this, new Handler());
        getContext().getContentResolver().registerContentObserver(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, true, mMusicObserver);

    }


    if(takeContentChanged() || mCache == null) {
        forceLoad();

    }

}

@Override
protected void onReset() {
    // Close any cursors, web-sockets or database objects
    if(mMusicObserver != null) {
        getContext().getContentResolver().unregisterContentObserver(mMusicObserver);
        mMusicObserver = null;
    }
}

/**
 * Simple observer that notifies the loader when it has detected a change.
 */
private  class MusicObserver extends ContentObserver {

    private android.support.v4.content.Loader mLoader;

    public MusicObserver(android.support.v4.content.Loader loader, Handler handler) {
        super(handler);
        mLoader = loader;
    }

    @Override
    public void onChange(boolean selfChange) {
        // A change has been detectec notify the Loader.

        mLoader.onContentChanged();
    }
}
}