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