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  * Interface for use with the {@link ValueAnimator#setEvaluator(TypeEvaluator)} function. Evaluators
21  * allow developers to create animations on arbitrary property types, by allowing them to supply
22  * custom evaluators for types that are not automatically understood and used by the animation
23  * system.
24  *
25  * @see ValueAnimator#setEvaluator(TypeEvaluator)
26  */
27 public interface TypeEvaluator<T> {
28 
29     /**
30      * This function returns the result of linearly interpolating the start and end values, with
31      * <code>fraction</code> representing the proportion between the start and end values. The
32      * calculation is a simple parametric calculation: <code>result = x0 + t * (x1 - x0)</code>,
33      * where <code>x0</code> is <code>startValue</code>, <code>x1</code> is <code>endValue</code>,
34      * and <code>t</code> is <code>fraction</code>.
35      *
36      * @param fraction   The fraction from the starting to the ending values
37      * @param startValue The start value.
38      * @param endValue   The end value.
39      * @return A linear interpolation between the start and end values, given the
40      *         <code>fraction</code> parameter.
41      */
evaluate(float fraction, T startValue, T endValue)42     public T evaluate(float fraction, T startValue, T endValue);
43 
44 }
45