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
17package 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 */
28public 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     */
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     */
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     */
77    boolean onMove(int oldPosition, int newPosition);
78}
79