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