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.PointF;
19
20/**
21 * This evaluator can be used to perform type interpolation between <code>PointF</code> values.
22 */
23public class PointFEvaluator implements TypeEvaluator<PointF> {
24
25    /**
26     * When null, a new PointF is returned on every evaluate call. When non-null,
27     * mPoint will be modified and returned on every evaluate.
28     */
29    private PointF mPoint;
30
31    /**
32     * Construct a PointFEvaluator that returns a new PointF on every evaluate call.
33     * To avoid creating an object for each evaluate call,
34     * {@link PointFEvaluator#PointFEvaluator(android.graphics.PointF)} should be used
35     * whenever possible.
36     */
37    public PointFEvaluator() {
38    }
39
40    /**
41     * Constructs a PointFEvaluator that modifies and returns <code>reuse</code>
42     * in {@link #evaluate(float, android.graphics.PointF, android.graphics.PointF)} calls.
43     * The value returned from
44     * {@link #evaluate(float, android.graphics.PointF, android.graphics.PointF)} should
45     * not be cached because it will change over time as the object is reused on each
46     * call.
47     *
48     * @param reuse A PointF to be modified and returned by evaluate.
49     */
50    public PointFEvaluator(PointF reuse) {
51        mPoint = reuse;
52    }
53
54    /**
55     * This function returns the result of linearly interpolating the start and
56     * end PointF 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 PointF objects
59     * (x, y).
60     *
61     * <p>If {@link #PointFEvaluator(android.graphics.PointF)} was used to construct
62     * this PointFEvaluator, the object returned will be the <code>reuse</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 PointF
67     * @param endValue   The end PointF
68     * @return A linear interpolation between the start and end values, given the
69     *         <code>fraction</code> parameter.
70     */
71    @Override
72    public PointF evaluate(float fraction, PointF startValue, PointF endValue) {
73        float x = startValue.x + (fraction * (endValue.x - startValue.x));
74        float y = startValue.y + (fraction * (endValue.y - startValue.y));
75
76        if (mPoint != null) {
77            mPoint.set(x, y);
78            return mPoint;
79        } else {
80            return new PointF(x, y);
81        }
82    }
83}
84