Implementing AsyncQueryHandler

问题

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?

回答1:

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

回答2:

It's so convenient:

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

回答3:

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.

回答4:

 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);

来源：https://stackoverflow.com/questions/11961857/implementing-asyncqueryhandler

标签

android

android-handler