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 
17 package com.android.contacts.util;
18 
19 import android.content.AsyncQueryHandler;
20 import android.content.Context;
21 import android.database.Cursor;
22 
23 import 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  */
33 public class NotifyingAsyncQueryHandler extends AsyncQueryHandler {
34     private WeakReference<AsyncQueryListener> mListener;
35 
36     /**
37      * Interface to listen for completed query operations.
38      */
39     public interface AsyncQueryListener {
onQueryComplete(int token, Object cookie, Cursor cursor)40         void onQueryComplete(int token, Object cookie, Cursor cursor);
41     }
42 
NotifyingAsyncQueryHandler(Context context, AsyncQueryListener listener)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      */
setQueryListener(AsyncQueryListener listener)52     public void setQueryListener(AsyncQueryListener listener) {
53         mListener = new WeakReference<AsyncQueryListener>(listener);
54     }
55 
56     /** {@inheritDoc} */
57     @Override
onQueryComplete(int token, Object cookie, Cursor cursor)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