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 package android.animation;
17 
18 import android.graphics.PointF;
19 
20 /**
21  * This evaluator can be used to perform type interpolation between <code>PointF</code> values.
22  */
23 public 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      */
PointFEvaluator()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      */
PointFEvaluator(PointF reuse)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
evaluate(float fraction, PointF startValue, PointF endValue)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