1 /* 2 * Copyright (C) 2017 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 androidx.transition; 18 19 import android.graphics.Path; 20 import android.graphics.PathMeasure; 21 import android.graphics.PointF; 22 import android.util.Property; 23 24 /** 25 * A special {@link Property} that can animate a pair of properties bi-dimensionally along the 26 * specified path. 27 * <p> 28 * This property should always be used with Animator that sets float fractions between 29 * {@code 0.f} and {@code 1.f}. For example, setting {@code 0.5f} to this property sets the 30 * values right in the middle of the specified path to the underlying properties. 31 * <p> 32 * Unlike many of the platform built-in properties, instances of this class cannot be reused 33 * for later animations. 34 */ 35 class PathProperty<T> extends Property<T, Float> { 36 37 private final Property<T, PointF> mProperty; 38 private final PathMeasure mPathMeasure; 39 private final float mPathLength; 40 private final float[] mPosition = new float[2]; 41 private final PointF mPointF = new PointF(); 42 private float mCurrentFraction; 43 44 PathProperty(Property<T, PointF> property, Path path) { 45 super(Float.class, property.getName()); 46 mProperty = property; 47 mPathMeasure = new PathMeasure(path, false); 48 mPathLength = mPathMeasure.getLength(); 49 } 50 51 @Override 52 public Float get(T object) { 53 return mCurrentFraction; 54 } 55 56 @Override 57 public void set(T target, Float fraction) { 58 mCurrentFraction = fraction; 59 mPathMeasure.getPosTan(mPathLength * fraction, mPosition, null); 60 mPointF.x = mPosition[0]; 61 mPointF.y = mPosition[1]; 62 mProperty.set(target, mPointF); 63 } 64 65 } 66
