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
17package android.support.transition;
18
19import android.graphics.Path;
20import android.graphics.PathMeasure;
21import android.graphics.PointF;
22import 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 */
35class 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