1 /*
2  * Copyright (C) 2008 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.database;
18 
19 /**
20  * A cross process cursor is an extension of a {@link Cursor} that also supports
21  * usage from remote processes.
22  * <p>
23  * The contents of a cross process cursor are marshalled to the remote process by
24  * filling {@link CursorWindow} objects using {@link #fillWindow}.  As an optimization,
25  * the cursor can provide a pre-filled window to use via {@link #getWindow} thereby
26  * obviating the need to copy the data to yet another cursor window.
27  */
28 public interface CrossProcessCursor extends Cursor {
29     /**
30      * Returns a pre-filled window that contains the data within this cursor.
31      * <p>
32      * In particular, the window contains the row indicated by {@link Cursor#getPosition}.
33      * The window's contents are automatically scrolled whenever the current
34      * row moved outside the range covered by the window.
35      * </p>
36      *
37      * @return The pre-filled window, or null if none.
38      */
getWindow()39     CursorWindow getWindow();
40 
41     /**
42      * Copies cursor data into the window.
43      * <p>
44      * Clears the window and fills it with data beginning at the requested
45      * row position until all of the data in the cursor is exhausted
46      * or the window runs out of space.
47      * </p><p>
48      * The filled window uses the same row indices as the original cursor.
49      * For example, if you fill a window starting from row 5 from the cursor,
50      * you can query the contents of row 5 from the window just by asking it
51      * for row 5 because there is a direct correspondence between the row indices
52      * used by the cursor and the window.
53      * </p><p>
54      * The current position of the cursor, as returned by {@link #getPosition},
55      * is not changed by this method.
56      * </p>
57      *
58      * @param position The zero-based index of the first row to copy into the window.
59      * @param window The window to fill.
60      */
fillWindow(int position, CursorWindow window)61     void fillWindow(int position, CursorWindow window);
62 
63     /**
64      * This function is called every time the cursor is successfully scrolled
65      * to a new position, giving the subclass a chance to update any state it
66      * may have.  If it returns false the move function will also do so and the
67      * cursor will scroll to the beforeFirst position.
68      * <p>
69      * This function should be called by methods such as {@link #moveToPosition(int)},
70      * so it will typically not be called from outside of the cursor class itself.
71      * </p>
72      *
73      * @param oldPosition The position that we're moving from.
74      * @param newPosition The position that we're moving to.
75      * @return True if the move is successful, false otherwise.
76      */
onMove(int oldPosition, int newPosition)77     boolean onMove(int oldPosition, int newPosition);
78 }
79