1/*
2 * Copyright (C) 2013 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.animation;
17
18import android.graphics.Rect;
19
20/**
21 * This evaluator can be used to perform type interpolation between <code>Rect</code> values.
22 */
23public class RectEvaluator implements TypeEvaluator<Rect> {
24
25    /**
26     * When null, a new Rect is returned on every evaluate call. When non-null,
27     * mRect will be modified and returned on every evaluate.
28     */
29    private Rect mRect;
30
31    /**
32     * Construct a RectEvaluator that returns a new Rect on every evaluate call.
33     * To avoid creating an object for each evaluate call,
34     * {@link RectEvaluator#RectEvaluator(android.graphics.Rect)} should be used
35     * whenever possible.
36     */
37    public RectEvaluator() {
38    }
39
40    /**
41     * Constructs a RectEvaluator that modifies and returns <code>reuseRect</code>
42     * in {@link #evaluate(float, android.graphics.Rect, android.graphics.Rect)} calls.
43     * The value returned from
44     * {@link #evaluate(float, android.graphics.Rect, android.graphics.Rect)} should
45     * not be cached because it will change over time as the object is reused on each
46     * call.
47     *
48     * @param reuseRect A Rect to be modified and returned by evaluate.
49     */
50    public RectEvaluator(Rect reuseRect) {
51        mRect = reuseRect;
52    }
53
54    /**
55     * This function returns the result of linearly interpolating the start and
56     * end Rect values, with <code>fraction</code> representing the proportion
57     * between the start and end values. The calculation is a simple parametric
58     * calculation on each of the separate components in the Rect objects
59     * (left, top, right, and bottom).
60     *
61     * <p>If {@link #RectEvaluator(android.graphics.Rect)} was used to construct
62     * this RectEvaluator, the object returned will be the <code>reuseRect</code>
63     * passed into the constructor.</p>
64     *
65     * @param fraction   The fraction from the starting to the ending values
66     * @param startValue The start Rect
67     * @param endValue   The end Rect
68     * @return A linear interpolation between the start and end values, given the
69     *         <code>fraction</code> parameter.
70     */
71    @Override
72    public Rect evaluate(float fraction, Rect startValue, Rect endValue) {
73        int left = startValue.left + (int) ((endValue.left - startValue.left) * fraction);
74        int top = startValue.top + (int) ((endValue.top - startValue.top) * fraction);
75        int right = startValue.right + (int) ((endValue.right - startValue.right) * fraction);
76        int bottom = startValue.bottom + (int) ((endValue.bottom - startValue.bottom) * fraction);
77        if (mRect == null) {
78            return new Rect(left, top, right, bottom);
79        } else {
80            mRect.set(left, top, right, bottom);
81            return mRect;
82        }
83    }
84}
85