1/*
2 * Copyright (C) 2014 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 */
16package android.transition;
17
18import android.content.Context;
19import android.graphics.Path;
20import android.util.AttributeSet;
21
22/**
23 * This base class can be extended to provide motion along a Path to Transitions.
24 *
25 * <p>
26 * Transitions such as {@link android.transition.ChangeBounds} move Views, typically
27 * in a straight path between the start and end positions. Applications that desire to
28 * have these motions move in a curve can change how Views interpolate in two dimensions
29 * by extending PathMotion and implementing {@link #getPath(float, float, float, float)}.
30 * </p>
31 * <p>This may be used in XML as an element inside a transition.</p>
32 * <pre>
33 * {@code
34 * <changeBounds>
35 *     <pathMotion class="my.app.transition.MyPathMotion"/>
36 * </changeBounds>
37 * }
38 * </pre>
39 */
40public abstract class PathMotion {
41
42    public PathMotion() {}
43
44    public PathMotion(Context context, AttributeSet attrs) {}
45
46    /**
47     * Provide a Path to interpolate between two points <code>(startX, startY)</code> and
48     * <code>(endX, endY)</code>. This allows controlled curved motion along two dimensions.
49     *
50     * @param startX The x coordinate of the starting point.
51     * @param startY The y coordinate of the starting point.
52     * @param endX   The x coordinate of the ending point.
53     * @param endY   The y coordinate of the ending point.
54     * @return A Path along which the points should be interpolated. The returned Path
55     * must start at point <code>(startX, startY)</code>, typically using
56     * {@link android.graphics.Path#moveTo(float, float)} and end at <code>(endX, endY)</code>.
57     */
58    public abstract Path getPath(float startX, float startY, float endX, float endY);
59}
60