1 /*
2  * Copyright (C) 2014 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.Path;
19 import android.graphics.PointF;
20 
21 import java.util.ArrayList;
22 
23 /**
24  * PathKeyframes relies on approximating the Path as a series of line segments.
25  * The line segments are recursively divided until there is less than 1/2 pixel error
26  * between the lines and the curve. Each point of the line segment is converted
27  * to a Keyframe and a linear interpolation between Keyframes creates a good approximation
28  * of the curve.
29  * <p>
30  * PathKeyframes is optimized to reduce the number of objects created when there are
31  * many keyframes for a curve.
32  * </p>
33  * <p>
34  * Typically, the returned type is a PointF, but the individual components can be extracted
35  * as either an IntKeyframes or FloatKeyframes.
36  * </p>
37  * @hide
38  */
39 public class PathKeyframes implements Keyframes {
40     private static final int FRACTION_OFFSET = 0;
41     private static final int X_OFFSET = 1;
42     private static final int Y_OFFSET = 2;
43     private static final int NUM_COMPONENTS = 3;
44     private static final ArrayList<Keyframe> EMPTY_KEYFRAMES = new ArrayList<Keyframe>();
45 
46     private PointF mTempPointF = new PointF();
47     private float[] mKeyframeData;
48 
PathKeyframes(Path path)49     public PathKeyframes(Path path) {
50         this(path, 0.5f);
51     }
52 
PathKeyframes(Path path, float error)53     public PathKeyframes(Path path, float error) {
54         if (path == null || path.isEmpty()) {
55             throw new IllegalArgumentException("The path must not be null or empty");
56         }
57         mKeyframeData = path.approximate(error);
58     }
59 
60     @Override
getKeyframes()61     public ArrayList<Keyframe> getKeyframes() {
62         return EMPTY_KEYFRAMES;
63     }
64 
65     @Override
getValue(float fraction)66     public Object getValue(float fraction) {
67         int numPoints = mKeyframeData.length / 3;
68         if (fraction < 0) {
69             return interpolateInRange(fraction, 0, 1);
70         } else if (fraction > 1) {
71             return interpolateInRange(fraction, numPoints - 2, numPoints - 1);
72         } else if (fraction == 0) {
73             return pointForIndex(0);
74         } else if (fraction == 1) {
75             return pointForIndex(numPoints - 1);
76         } else {
77             // Binary search for the correct section
78             int low = 0;
79             int high = numPoints - 1;
80 
81             while (low <= high) {
82                 int mid = (low + high) / 2;
83                 float midFraction = mKeyframeData[(mid * NUM_COMPONENTS) + FRACTION_OFFSET];
84 
85                 if (fraction < midFraction) {
86                     high = mid - 1;
87                 } else if (fraction > midFraction) {
88                     low = mid + 1;
89                 } else {
90                     return pointForIndex(mid);
91                 }
92             }
93 
94             // now high is below the fraction and low is above the fraction
95             return interpolateInRange(fraction, high, low);
96         }
97     }
98 
interpolateInRange(float fraction, int startIndex, int endIndex)99     private PointF interpolateInRange(float fraction, int startIndex, int endIndex) {
100         int startBase = (startIndex * NUM_COMPONENTS);
101         int endBase = (endIndex * NUM_COMPONENTS);
102 
103         float startFraction = mKeyframeData[startBase + FRACTION_OFFSET];
104         float endFraction = mKeyframeData[endBase + FRACTION_OFFSET];
105 
106         float intervalFraction = (fraction - startFraction)/(endFraction - startFraction);
107 
108         float startX = mKeyframeData[startBase + X_OFFSET];
109         float endX = mKeyframeData[endBase + X_OFFSET];
110         float startY = mKeyframeData[startBase + Y_OFFSET];
111         float endY = mKeyframeData[endBase + Y_OFFSET];
112 
113         float x = interpolate(intervalFraction, startX, endX);
114         float y = interpolate(intervalFraction, startY, endY);
115 
116         mTempPointF.set(x, y);
117         return mTempPointF;
118     }
119 
120     @Override
setEvaluator(TypeEvaluator evaluator)121     public void setEvaluator(TypeEvaluator evaluator) {
122     }
123 
124     @Override
getType()125     public Class getType() {
126         return PointF.class;
127     }
128 
129     @Override
clone()130     public Keyframes clone() {
131         Keyframes clone = null;
132         try {
133             clone = (Keyframes) super.clone();
134         } catch (CloneNotSupportedException e) {}
135         return clone;
136     }
137 
pointForIndex(int index)138     private PointF pointForIndex(int index) {
139         int base = (index * NUM_COMPONENTS);
140         int xOffset = base + X_OFFSET;
141         int yOffset = base + Y_OFFSET;
142         mTempPointF.set(mKeyframeData[xOffset], mKeyframeData[yOffset]);
143         return mTempPointF;
144     }
145 
interpolate(float fraction, float startValue, float endValue)146     private static float interpolate(float fraction, float startValue, float endValue) {
147         float diff = endValue - startValue;
148         return startValue + (diff * fraction);
149     }
150 
151     /**
152      * Returns a FloatKeyframes for the X component of the Path.
153      * @return a FloatKeyframes for the X component of the Path.
154      */
createXFloatKeyframes()155     public FloatKeyframes createXFloatKeyframes() {
156         return new FloatKeyframesBase() {
157             @Override
158             public float getFloatValue(float fraction) {
159                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
160                 return pointF.x;
161             }
162         };
163     }
164 
165     /**
166      * Returns a FloatKeyframes for the Y component of the Path.
167      * @return a FloatKeyframes for the Y component of the Path.
168      */
169     public FloatKeyframes createYFloatKeyframes() {
170         return new FloatKeyframesBase() {
171             @Override
172             public float getFloatValue(float fraction) {
173                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
174                 return pointF.y;
175             }
176         };
177     }
178 
179     /**
180      * Returns an IntKeyframes for the X component of the Path.
181      * @return an IntKeyframes for the X component of the Path.
182      */
183     public IntKeyframes createXIntKeyframes() {
184         return new IntKeyframesBase() {
185             @Override
186             public int getIntValue(float fraction) {
187                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
188                 return Math.round(pointF.x);
189             }
190         };
191     }
192 
193     /**
194      * Returns an IntKeyframeSet for the Y component of the Path.
195      * @return an IntKeyframeSet for the Y component of the Path.
196      */
197     public IntKeyframes createYIntKeyframes() {
198         return new IntKeyframesBase() {
199             @Override
200             public int getIntValue(float fraction) {
201                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
202                 return Math.round(pointF.y);
203             }
204         };
205     }
206 
207     private abstract static class SimpleKeyframes implements Keyframes {
208         @Override
209         public void setEvaluator(TypeEvaluator evaluator) {
210         }
211 
212         @Override
213         public ArrayList<Keyframe> getKeyframes() {
214             return EMPTY_KEYFRAMES;
215         }
216 
217         @Override
218         public Keyframes clone() {
219             Keyframes clone = null;
220             try {
221                 clone = (Keyframes) super.clone();
222             } catch (CloneNotSupportedException e) {}
223             return clone;
224         }
225     }
226 
227     abstract static class IntKeyframesBase extends SimpleKeyframes implements IntKeyframes {
228         @Override
229         public Class getType() {
230             return Integer.class;
231         }
232 
233         @Override
234         public Object getValue(float fraction) {
235             return getIntValue(fraction);
236         }
237     }
238 
239     abstract static class FloatKeyframesBase extends SimpleKeyframes
240             implements FloatKeyframes {
241         @Override
242         public Class getType() {
243             return Float.class;
244         }
245 
246         @Override
247         public Object getValue(float fraction) {
248             return getFloatValue(fraction);
249         }
250     }
251 }
252