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 com.example.android.curvedmotion; 17 18 import android.animation.TypeEvaluator; 19 20 /** 21 * This evaluator interpolates between two PathPoint values given the value t, the 22 * proportion traveled between those points. The value of the interpolation depends 23 * on the operation specified by the endValue (the operation for the interval between 24 * PathPoints is always specified by the end point of that interval). 25 */ 26 public class PathEvaluator implements TypeEvaluator<PathPoint> { 27 @Override 28 public PathPoint evaluate(float t, PathPoint startValue, PathPoint endValue) { 29 float x, y; 30 if (endValue.mOperation == PathPoint.CURVE) { 31 float oneMinusT = 1 - t; 32 x = oneMinusT * oneMinusT * oneMinusT * startValue.mX + 33 3 * oneMinusT * oneMinusT * t * endValue.mControl0X + 34 3 * oneMinusT * t * t * endValue.mControl1X + 35 t * t * t * endValue.mX; 36 y = oneMinusT * oneMinusT * oneMinusT * startValue.mY + 37 3 * oneMinusT * oneMinusT * t * endValue.mControl0Y + 38 3 * oneMinusT * t * t * endValue.mControl1Y + 39 t * t * t * endValue.mY; 40 } else if (endValue.mOperation == PathPoint.LINE) { 41 x = startValue.mX + t * (endValue.mX - startValue.mX); 42 y = startValue.mY + t * (endValue.mY - startValue.mY); 43 } else { 44 x = endValue.mX; 45 y = endValue.mY; 46 } 47 return PathPoint.moveTo(x, y); 48 } 49 } 50
