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1 | /* |
2 | * Copyright (C) 2011 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 android.support.v2.content; |
18 | |
19 | import android.content.Context; |
20 | import android.database.ContentObserver; |
21 | import android.database.Cursor; |
22 | import android.net.Uri; |
23 | |
24 | import java.io.FileDescriptor; |
25 | import java.io.PrintWriter; |
26 | import java.util.Arrays; |
27 | |
28 | /** |
29 | * Static library support version of the framework's {@link android.content.CursorLoader}. |
30 | * Used to write apps that run on platforms prior to Android 3.0. When running |
31 | * on Android 3.0 or above, this implementation is still used; it does not try |
32 | * to switch to the framework's implementation. See the framework SDK |
33 | * documentation for a class overview. |
34 | */ |
35 | public class CursorLoader extends AsyncTaskLoader<Cursor> { |
36 | final ForceLoadContentObserver mObserver; |
37 | |
38 | Uri mUri; |
39 | String[] mProjection; |
40 | String mSelection; |
41 | String[] mSelectionArgs; |
42 | String mSortOrder; |
43 | |
44 | Cursor mCursor; |
45 | |
46 | /* Runs on a worker thread */ |
47 | @Override |
48 | public Cursor loadInBackground() { |
49 | Cursor cursor = getContext().getContentResolver().query(mUri, mProjection, mSelection, |
50 | mSelectionArgs, mSortOrder); |
51 | if (cursor != null) { |
52 | // Ensure the cursor window is filled |
53 | cursor.getCount(); |
54 | registerContentObserver(cursor, mObserver); |
55 | } |
56 | return cursor; |
57 | } |
58 | |
59 | /** |
60 | * Registers an observer to get notifications from the content provider |
61 | * when the cursor needs to be refreshed. |
62 | */ |
63 | void registerContentObserver(Cursor cursor, ContentObserver observer) { |
64 | cursor.registerContentObserver(mObserver); |
65 | } |
66 | |
67 | /* Runs on the UI thread */ |
68 | @Override |
69 | public void deliverResult(Cursor cursor) { |
70 | if (isReset()) { |
71 | // An async query came in while the loader is stopped |
72 | if (cursor != null) { |
73 | cursor.close(); |
74 | } |
75 | return; |
76 | } |
77 | Cursor oldCursor = mCursor; |
78 | mCursor = cursor; |
79 | |
80 | if (isStarted()) { |
81 | super.deliverResult(cursor); |
82 | } |
83 | |
84 | if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) { |
85 | oldCursor.close(); |
86 | } |
87 | } |
88 | |
89 | /** |
90 | * Creates an empty unspecified CursorLoader. You must follow this with |
91 | * calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc |
92 | * to specify the query to perform. |
93 | */ |
94 | public CursorLoader(Context context) { |
95 | super(context); |
96 | mObserver = new ForceLoadContentObserver(); |
97 | } |
98 | |
99 | /** |
100 | * Creates a fully-specified CursorLoader. See |
101 | * {@link ContentResolver#query(Uri, String[], String, String[], String) |
102 | * ContentResolver.query()} for documentation on the meaning of the |
103 | * parameters. These will be passed as-is to that call. |
104 | */ |
105 | public CursorLoader(Context context, Uri uri, String[] projection, String selection, |
106 | String[] selectionArgs, String sortOrder) { |
107 | super(context); |
108 | mObserver = new ForceLoadContentObserver(); |
109 | mUri = uri; |
110 | mProjection = projection; |
111 | mSelection = selection; |
112 | mSelectionArgs = selectionArgs; |
113 | mSortOrder = sortOrder; |
114 | } |
115 | |
116 | /** |
117 | * Starts an asynchronous load of the contacts list data. When the result is ready the callbacks |
118 | * will be called on the UI thread. If a previous load has been completed and is still valid |
119 | * the result may be passed to the callbacks immediately. |
120 | * |
121 | * Must be called from the UI thread |
122 | */ |
123 | @Override |
124 | protected void onStartLoading() { |
125 | if (mCursor != null) { |
126 | deliverResult(mCursor); |
127 | } |
128 | if (takeContentChanged() || mCursor == null) { |
129 | forceLoad(); |
130 | } |
131 | } |
132 | |
133 | /** |
134 | * Must be called from the UI thread |
135 | */ |
136 | @Override |
137 | protected void onStopLoading() { |
138 | // Attempt to cancel the current load task if possible. |
139 | cancelLoad(); |
140 | } |
141 | |
142 | @Override |
143 | public void onCanceled(Cursor cursor) { |
144 | if (cursor != null && !cursor.isClosed()) { |
145 | cursor.close(); |
146 | } |
147 | } |
148 | |
149 | @Override |
150 | protected void onReset() { |
151 | super.onReset(); |
152 | |
153 | // Ensure the loader is stopped |
154 | onStopLoading(); |
155 | |
156 | if (mCursor != null && !mCursor.isClosed()) { |
157 | mCursor.close(); |
158 | } |
159 | mCursor = null; |
160 | } |
161 | |
162 | public Uri getUri() { |
163 | return mUri; |
164 | } |
165 | |
166 | public void setUri(Uri uri) { |
167 | mUri = uri; |
168 | } |
169 | |
170 | public String[] getProjection() { |
171 | return mProjection; |
172 | } |
173 | |
174 | public void setProjection(String[] projection) { |
175 | mProjection = projection; |
176 | } |
177 | |
178 | public String getSelection() { |
179 | return mSelection; |
180 | } |
181 | |
182 | public void setSelection(String selection) { |
183 | mSelection = selection; |
184 | } |
185 | |
186 | public String[] getSelectionArgs() { |
187 | return mSelectionArgs; |
188 | } |
189 | |
190 | public void setSelectionArgs(String[] selectionArgs) { |
191 | mSelectionArgs = selectionArgs; |
192 | } |
193 | |
194 | public String getSortOrder() { |
195 | return mSortOrder; |
196 | } |
197 | |
198 | public void setSortOrder(String sortOrder) { |
199 | mSortOrder = sortOrder; |
200 | } |
201 | |
202 | @Override |
203 | public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { |
204 | super.dump(prefix, fd, writer, args); |
205 | writer.print(prefix); writer.print("mUri="); writer.println(mUri); |
206 | writer.print(prefix); writer.print("mProjection="); |
207 | writer.println(Arrays.toString(mProjection)); |
208 | writer.print(prefix); writer.print("mSelection="); writer.println(mSelection); |
209 | writer.print(prefix); writer.print("mSelectionArgs="); |
210 | writer.println(Arrays.toString(mSelectionArgs)); |
211 | writer.print(prefix); writer.print("mSortOrder="); writer.println(mSortOrder); |
212 | writer.print(prefix); writer.print("mCursor="); writer.println(mCursor); |
213 | writer.print(prefix); writer.print("mContentChanged="); writer.println(mContentChanged); |
214 | } |
215 | } |