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
17package 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 */
27public 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     */
42    public T evaluate(float fraction, T startValue, T endValue);
43
44}
45