Implementing AsyncQueryHandler

Question

I am trying to implement AsyncQueryHandler because I am experiencing the same exact problem in this link but I dont see any example or anything about implementing it.

I tried doing

AsyncQueryHandler handler = new AsyncQueryHandler(getContentResolver());

since that is what the constructor shows in the docs but I get an error saying cannot instantiate the type AsyncQueryHandler so how do I use it then?

Good place to start would be the AOSP source code. – JoxTraex Aug 14 '12 at 22:41 — JoxTraex, Aug 14 '12 at 22:41

score 17 · Answer 1 · edited Nov 17 '12 at 11:31

17

It's so convenient:

AsyncQueryHandler handler = 
    new AsyncQueryHandler(mActivity.getContentResolver()) {};
handler.startUpdate(-1, null, sessionUri, values, null, null);

edited Nov 17 '12 at 11:31

rolve

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answered Nov 13 '12 at 02:40

Crossle Song

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1

I get this warning when I try to do it `This Handler class should be static or leaks might occur` – Adeel Ahmad Mar 09 '20 at 20:46

score 12 · Answer 2 · answered May 24 '13 at 00:20

It comes very handy when you need to do CRUD operationa async without using a Loader, so by extending from asyncquery you get method such as startQuery, startInsert, startUpdate and startDelete an easy implementation could be:

public class CustomAsyncHandler extends AsyncQueryHandler {

        private WeakReference<AsyncQueryListener> mListener;

        public interface AsyncQueryListener {
            void onQueryComplete(int token, Object cookie, Cursor cursor);
        }

        public CustomAsyncHandler(ContentResolver cr, AsyncQueryListener listener) {
            super(cr);
            mListener = new WeakReference<AsyncQueryListener>(listener);
        }

        public CustomAsyncHandler(ContentResolver cr) {
            super(cr);
        }

        /**
         * Assign the given {@link AsyncQueryListener} to receive query events from
         * asynchronous calls. Will replace any existing listener.
         */
        public void setQueryListener(AsyncQueryListener listener) {
            mListener = new WeakReference<AsyncQueryListener>(listener);
        }

        /** {@inheritDoc} */
        @Override
        protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
            final AsyncQueryListener listener = mListener.get();
            if (listener != null) {
                listener.onQueryComplete(token, cookie, cursor);
            } else if (cursor != null) {
                cursor.close();
            }
        }

    }

As you can see there is an extra interface AsyncQueryListener created to be as a callback when query is completed, as this you can create AsyncUpdateListener, AsyncDeleteListener, AsyncInsertListener, and so on.

Why would you not want to use a Loader when doing CRUD operations? — IgorGanapolsky, Dec 05 '13 at 21:57
As AsyncQueryHandler already has its own onQueryComplete() method, why is there any need to use AsyncQueryListener? — Gruntcakes, Feb 11 '15 at 17:45
The extra listener interface is because you need to propagate the event back to the instantiating class. — Stephen Kaiser, Jul 14 '15 at 05:34
simple and elegant, 10x, but why using WeakReference? no potential memory abuse in this case.. — gor, Jan 28 '16 at 07:06
@gor If you use this class as static inner class, then WeakReference will be in handy. — zkvarz, Feb 13 '18 at 14:04
The WeakReference goes beyond "memory abuse" and helps protect you from situations where the calling class has been destroyed before you get the query result. — Brendon Whateley, Apr 06 '18 at 00:30

score 11 · Accepted Answer · answered Aug 14 '12 at 22:42

11

AsyncQueryHandler is an abstract class, thus you cannot instantiate it directly. You need to subclass it.

answered Aug 14 '12 at 22:42

Tyler Treat

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score 0 · Answer 4 · answered Jun 18 '17 at 15:07

 AsyncQueryHandler asyncQueryHandler = new AsyncQueryHandler(activity.getContentResolver()){

        @Override
        protected void onInsertComplete(int token, Object cookie, Uri uri) {
            super.onInsertComplete(token, cookie, uri);
            Log.d(TAG, "onInsertComplete  return uri: " + uri);
        }

 };

 asyncQueryHandler.startInsert(-1, null, mUri, values);

Implementing AsyncQueryHandler

4 Answers4

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