CursorLoader.java revision 8e6f69b08fa3be56ad11aaffbecbcbead49afd33 
1/*
2 * Copyright (C) 2010 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 android.content;
18
19import android.database.Cursor;
20import android.net.Uri;
21
22/**
23 * A loader that queries the {@link ContentResolver} and returns a {@link Cursor}.
24 */
25public class CursorLoader extends AsyncTaskLoader<Cursor> {
26    Cursor mCursor;
27    ForceLoadContentObserver mObserver;
28    boolean mStopped;
29    Uri mUri;
30    String[] mProjection;
31    String mSelection;
32    String[] mSelectionArgs;
33    String mSortOrder;
34
35    /* Runs on a worker thread */
36    @Override
37    public Cursor loadInBackground() {
38        Cursor cursor = getContext().getContentResolver().query(mUri, mProjection, mSelection,
39                mSelectionArgs, mSortOrder);
40        // Ensure the cursor window is filled
41        if (cursor != null) {
42            cursor.getCount();
43            cursor.registerContentObserver(mObserver);
44        }
45        return cursor;
46    }
47
48    /* Runs on the UI thread */
49    @Override
50    public void deliverResult(Cursor cursor) {
51        if (mStopped) {
52            // An async query came in while the loader is stopped
53            if (cursor != null) {
54                cursor.close();
55            }
56            return;
57        }
58        Cursor oldCursor = mCursor;
59        mCursor = cursor;
60        super.deliverResult(cursor);
61
62        if (oldCursor != null && !oldCursor.isClosed()) {
63            oldCursor.close();
64        }
65    }
66
67    public CursorLoader(Context context, Uri uri, String[] projection, String selection,
68            String[] selectionArgs, String sortOrder) {
69        super(context);
70        mObserver = new ForceLoadContentObserver();
71        mUri = uri;
72        mProjection = projection;
73        mSelection = selection;
74        mSelectionArgs = selectionArgs;
75        mSortOrder = sortOrder;
76    }
77
78    /**
79     * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
80     * will be called on the UI thread. If a previous load has been completed and is still valid
81     * the result may be passed to the callbacks immediately.
82     *
83     * Must be called from the UI thread
84     */
85    @Override
86    public void startLoading() {
87        mStopped = false;
88
89        if (mCursor != null) {
90            deliverResult(mCursor);
91        } else {
92            forceLoad();
93        }
94    }
95
96    /**
97     * Must be called from the UI thread
98     */
99    @Override
100    public void stopLoading() {
101        if (mCursor != null && !mCursor.isClosed()) {
102            mCursor.close();
103            mCursor = null;
104        }
105
106        // Attempt to cancel the current load task if possible.
107        cancelLoad();
108
109        // Make sure that any outstanding loads clean themselves up properly
110        mStopped = true;
111    }
112
113    @Override
114    public void onCancelled(Cursor cursor) {
115        if (cursor != null && !cursor.isClosed()) {
116            cursor.close();
117        }
118    }
119
120    @Override
121    public void destroy() {
122        // Ensure the loader is stopped
123        stopLoading();
124    }
125
126    public Uri getUri() {
127        return mUri;
128    }
129
130    public void setUri(Uri uri) {
131        mUri = uri;
132    }
133
134    public String[] getProjection() {
135        return mProjection;
136    }
137
138    public void setProjection(String[] projection) {
139        mProjection = projection;
140    }
141
142    public String getSelection() {
143        return mSelection;
144    }
145
146    public void setSelection(String selection) {
147        mSelection = selection;
148    }
149
150    public String[] getSelectionArgs() {
151        return mSelectionArgs;
152    }
153
154    public void setSelectionArgs(String[] selectionArgs) {
155        mSelectionArgs = selectionArgs;
156    }
157
158    public String getSortOrder() {
159        return mSortOrder;
160    }
161
162    public void setSortOrder(String sortOrder) {
163        mSortOrder = sortOrder;
164    }
165}
166