Android: How to detect a change in MediaStore when connected over MTP

Question

I have big problems with MediaStore. I need to handle events when MediaStore is changed over MTP. I already have a receiver for android.intent.action.MEDIA_SCANNER_FIN

Answer 1

I finally found a solution. I tried to use FileObserver but when you use it for all directories...it is quite memory consuming. So now I am using ContentObserver and it is working well:

public static class UriObserver
{
    private final Cursor mCursor;
    private final ContentObserver mObserver;
    private boolean mRunning = true;

    private class ObserverWithListener extends ContentObserver
    {
        private final OnChangeListener mListener;

        public ObserverWithListener(OnChangeListener listener)
        {
            super(new Handler());

            mListener = listener;
        }

        @Override
        public void onChange(boolean selfChange)
        {
            if (mRunning)
            {
                log.d("Change triggered");
                mListener.onChange();
            }
        }
    };

    public static UriObserver getInstance(ContentResolver contentResolver, Uri uri, OnChangeListener listener)
    {
        Cursor c = contentResolver.query(uri, new String[] { "*" }, null, null, null);

        if ((c = Dao.moveToFirst(c)) == null)
        {
            log.e("Cannot start observer for uri: " + uri);
            return null;
        }

        return new UriObserver(c, listener);
    }

    public UriObserver(Cursor c, final OnChangeListener listener)
    {
        mCursor = c;
        mObserver = new ObserverWithListener(listener);
        mCursor.registerContentObserver(mObserver);
    }

    public void stop()
    {
        mCursor.unregisterContentObserver(mObserver);
        Dao.closeCursor(mCursor);
        mRunning = false;
    }

    public interface OnChangeListener
    {
        public void onChange();
    }
}

The flag mRunning has to be there for some reason because onChange was sometimes called even if unregisterContentObserver() had been called before.

This code I am using with Uris that I want to observe, i.e. MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, ...