1 /*
2  * Copyright (C) 2010 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 
17 package android.animation;
18 
19 /**
20  * This evaluator can be used to perform type interpolation between <code>float</code> values.
21  */
22 public class FloatEvaluator implements TypeEvaluator<Number> {
23 
24     /**
25      * This function returns the result of linearly interpolating the start and end values, with
26      * <code>fraction</code> representing the proportion between the start and end values. The
27      * calculation is a simple parametric calculation: <code>result = x0 + t * (x1 - x0)</code>,
28      * where <code>x0</code> is <code>startValue</code>, <code>x1</code> is <code>endValue</code>,
29      * and <code>t</code> is <code>fraction</code>.
30      *
31      * @param fraction   The fraction from the starting to the ending values
32      * @param startValue The start value; should be of type <code>float</code> or
33      *                   <code>Float</code>
34      * @param endValue   The end value; should be of type <code>float</code> or <code>Float</code>
35      * @return A linear interpolation between the start and end values, given the
36      *         <code>fraction</code> parameter.
37      */
evaluate(float fraction, Number startValue, Number endValue)38     public Float evaluate(float fraction, Number startValue, Number endValue) {
39         float startFloat = startValue.floatValue();
40         return startFloat + fraction * (endValue.floatValue() - startFloat);
41     }
42 }