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 */
16
17package android.animation;
18
19/**
20 * This evaluator can be used to perform type interpolation between <code>float[]</code> values.
21 * Each index into the array is treated as a separate value to interpolate. For example,
22 * evaluating <code>{100, 200}</code> and <code>{300, 400}</code> will interpolate the value at
23 * the first index between 100 and 300 and the value at the second index value between 200 and 400.
24 */
25public class FloatArrayEvaluator implements TypeEvaluator<float[]> {
26
27    private float[] mArray;
28
29    /**
30     * Create a FloatArrayEvaluator that does not reuse the animated value. Care must be taken
31     * when using this option because on every evaluation a new <code>float[]</code> will be
32     * allocated.
33     *
34     * @see #FloatArrayEvaluator(float[])
35     */
36    public FloatArrayEvaluator() {
37    }
38
39    /**
40     * Create a FloatArrayEvaluator that reuses <code>reuseArray</code> for every evaluate() call.
41     * Caution must be taken to ensure that the value returned from
42     * {@link android.animation.ValueAnimator#getAnimatedValue()} is not cached, modified, or
43     * used across threads. The value will be modified on each <code>evaluate()</code> call.
44     *
45     * @param reuseArray The array to modify and return from <code>evaluate</code>.
46     */
47    public FloatArrayEvaluator(float[] reuseArray) {
48        mArray = reuseArray;
49    }
50
51    /**
52     * Interpolates the value at each index by the fraction. If
53     * {@link #FloatArrayEvaluator(float[])} was used to construct this object,
54     * <code>reuseArray</code> will be returned, otherwise a new <code>float[]</code>
55     * will be returned.
56     *
57     * @param fraction   The fraction from the starting to the ending values
58     * @param startValue The start value.
59     * @param endValue   The end value.
60     * @return A <code>float[]</code> where each element is an interpolation between
61     *         the same index in startValue and endValue.
62     */
63    @Override
64    public float[] evaluate(float fraction, float[] startValue, float[] endValue) {
65        float[] array = mArray;
66        if (array == null) {
67            array = new float[startValue.length];
68        }
69
70        for (int i = 0; i < array.length; i++) {
71            float start = startValue[i];
72            float end = endValue[i];
73            array[i] = start + (fraction * (end - start));
74        }
75        return array;
76    }
77}
78