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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
invalidateCache()121     public void invalidateCache() {
122     }
123 
124     @Override
setEvaluator(TypeEvaluator evaluator)125     public void setEvaluator(TypeEvaluator evaluator) {
126     }
127 
128     @Override
getType()129     public Class getType() {
130         return PointF.class;
131     }
132 
133     @Override
clone()134     public Keyframes clone() {
135         Keyframes clone = null;
136         try {
137             clone = (Keyframes) super.clone();
138         } catch (CloneNotSupportedException e) {}
139         return clone;
140     }
141 
pointForIndex(int index)142     private PointF pointForIndex(int index) {
143         int base = (index * NUM_COMPONENTS);
144         int xOffset = base + X_OFFSET;
145         int yOffset = base + Y_OFFSET;
146         mTempPointF.set(mKeyframeData[xOffset], mKeyframeData[yOffset]);
147         return mTempPointF;
148     }
149 
interpolate(float fraction, float startValue, float endValue)150     private static float interpolate(float fraction, float startValue, float endValue) {
151         float diff = endValue - startValue;
152         return startValue + (diff * fraction);
153     }
154 
155     /**
156      * Returns a FloatKeyframes for the X component of the Path.
157      * @return a FloatKeyframes for the X component of the Path.
158      */
createXFloatKeyframes()159     public FloatKeyframes createXFloatKeyframes() {
160         return new FloatKeyframesBase() {
161             @Override
162             public float getFloatValue(float fraction) {
163                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
164                 return pointF.x;
165             }
166         };
167     }
168 
169     /**
170      * Returns a FloatKeyframes for the Y component of the Path.
171      * @return a FloatKeyframes for the Y component of the Path.
172      */
173     public FloatKeyframes createYFloatKeyframes() {
174         return new FloatKeyframesBase() {
175             @Override
176             public float getFloatValue(float fraction) {
177                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
178                 return pointF.y;
179             }
180         };
181     }
182 
183     /**
184      * Returns an IntKeyframes for the X component of the Path.
185      * @return an IntKeyframes for the X component of the Path.
186      */
187     public IntKeyframes createXIntKeyframes() {
188         return new IntKeyframesBase() {
189             @Override
190             public int getIntValue(float fraction) {
191                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
192                 return Math.round(pointF.x);
193             }
194         };
195     }
196 
197     /**
198      * Returns an IntKeyframeSet for the Y component of the Path.
199      * @return an IntKeyframeSet for the Y component of the Path.
200      */
201     public IntKeyframes createYIntKeyframes() {
202         return new IntKeyframesBase() {
203             @Override
204             public int getIntValue(float fraction) {
205                 PointF pointF = (PointF) PathKeyframes.this.getValue(fraction);
206                 return Math.round(pointF.y);
207             }
208         };
209     }
210 
211     private abstract static class SimpleKeyframes implements Keyframes {
212         @Override
213         public void setEvaluator(TypeEvaluator evaluator) {
214         }
215 
216         @Override
217         public void invalidateCache() {
218         }
219 
220         @Override
221         public ArrayList<Keyframe> getKeyframes() {
222             return EMPTY_KEYFRAMES;
223         }
224 
225         @Override
226         public Keyframes clone() {
227             Keyframes clone = null;
228             try {
229                 clone = (Keyframes) super.clone();
230             } catch (CloneNotSupportedException e) {}
231             return clone;
232         }
233     }
234 
235     abstract static class IntKeyframesBase extends SimpleKeyframes implements IntKeyframes {
236         @Override
237         public Class getType() {
238             return Integer.class;
239         }
240 
241         @Override
242         public Object getValue(float fraction) {
243             return getIntValue(fraction);
244         }
245     }
246 
247     abstract static class FloatKeyframesBase extends SimpleKeyframes
248             implements FloatKeyframes {
249         @Override
250         public Class getType() {
251             return Float.class;
252         }
253 
254         @Override
255         public Object getValue(float fraction) {
256             return getFloatValue(fraction);
257         }
258     }
259 }
260