NotifyingAsyncQueryHandler.java revision cde7389187ebc6816bd73d4704f1ca1b4ee39ac3 
1/*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.contacts.util;
18
19import android.content.AsyncQueryHandler;
20import android.content.Context;
21import android.database.Cursor;
22
23import java.lang.ref.WeakReference;
24
25/**
26 * Slightly more abstract {@link AsyncQueryHandler} that helps keep a
27 * {@link WeakReference} back to a listener. Will properly close any
28 * {@link Cursor} if the listener ceases to exist.
29 * <p>
30 * This pattern can be used to perform background queries without leaking
31 * {@link Context} objects.
32 */
33public class NotifyingAsyncQueryHandler extends AsyncQueryHandler {
34    private WeakReference<AsyncQueryListener> mListener;
35
36    /**
37     * Interface to listen for completed query operations.
38     */
39    public interface AsyncQueryListener {
40        void onQueryComplete(int token, Object cookie, Cursor cursor);
41    }
42
43    public NotifyingAsyncQueryHandler(Context context, AsyncQueryListener listener) {
44        super(context.getContentResolver());
45        setQueryListener(listener);
46    }
47
48    /**
49     * Assign the given {@link AsyncQueryListener} to receive query events from
50     * asynchronous calls. Will replace any existing listener.
51     */
52    public void setQueryListener(AsyncQueryListener listener) {
53        mListener = new WeakReference<AsyncQueryListener>(listener);
54    }
55
56    /** {@inheritDoc} */
57    @Override
58    protected void onQueryComplete(int token, Object cookie, Cursor cursor) {
59        final AsyncQueryListener listener = mListener.get();
60        if (listener != null) {
61            listener.onQueryComplete(token, cookie, cursor);
62        } else if (cursor != null) {
63            cursor.close();
64        }
65    }
66}
67