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.Rect; 19 20 /** 21 * This evaluator can be used to perform type interpolation between <code>Rect</code> values. 22 */ 23 public class RectEvaluator implements TypeEvaluator<Rect> { 24 25 /** 26 * When null, a new Rect is returned on every evaluate call. When non-null, 27 * mRect will be modified and returned on every evaluate. 28 */ 29 private Rect mRect; 30 31 /** 32 * Construct a RectEvaluator that returns a new Rect on every evaluate call. 33 * To avoid creating an object for each evaluate call, 34 * {@link RectEvaluator#RectEvaluator(android.graphics.Rect)} should be used 35 * whenever possible. 36 */ RectEvaluator()37 public RectEvaluator() { 38 } 39 40 /** 41 * Constructs a RectEvaluator that modifies and returns <code>reuseRect</code> 42 * in {@link #evaluate(float, android.graphics.Rect, android.graphics.Rect)} calls. 43 * The value returned from 44 * {@link #evaluate(float, android.graphics.Rect, android.graphics.Rect)} should 45 * not be cached because it will change over time as the object is reused on each 46 * call. 47 * 48 * @param reuseRect A Rect to be modified and returned by evaluate. 49 */ RectEvaluator(Rect reuseRect)50 public RectEvaluator(Rect reuseRect) { 51 mRect = reuseRect; 52 } 53 54 /** 55 * This function returns the result of linearly interpolating the start and 56 * end Rect 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 Rect objects 59 * (left, top, right, and bottom). 60 * 61 * <p>If {@link #RectEvaluator(android.graphics.Rect)} was used to construct 62 * this RectEvaluator, the object returned will be the <code>reuseRect</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 Rect 67 * @param endValue The end Rect 68 * @return A linear interpolation between the start and end values, given the 69 * <code>fraction</code> parameter. 70 */ 71 @Override evaluate(float fraction, Rect startValue, Rect endValue)72 public Rect evaluate(float fraction, Rect startValue, Rect endValue) { 73 int left = startValue.left + (int) ((endValue.left - startValue.left) * fraction); 74 int top = startValue.top + (int) ((endValue.top - startValue.top) * fraction); 75 int right = startValue.right + (int) ((endValue.right - startValue.right) * fraction); 76 int bottom = startValue.bottom + (int) ((endValue.bottom - startValue.bottom) * fraction); 77 if (mRect == null) { 78 return new Rect(left, top, right, bottom); 79 } else { 80 mRect.set(left, top, right, bottom); 81 return mRect; 82 } 83 } 84 } 85