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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 
     49     public PathKeyframes(Path path) {
     50         this(path, 0.5f);
     51     }
     52 
     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
     61     public ArrayList<Keyframe> getKeyframes() {
     62         return EMPTY_KEYFRAMES;
     63     }
     64 
     65     @Override
     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 
     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
    121     public void invalidateCache() {
    122     }
    123 
    124     @Override
    125     public void setEvaluator(TypeEvaluator evaluator) {
    126     }
    127 
    128     @Override
    129     public Class getType() {
    130         return PointF.class;
    131     }
    132 
    133     @Override
    134     public Keyframes clone() {
    135         Keyframes clone = null;
    136         try {
    137             clone = (Keyframes) super.clone();
    138         } catch (CloneNotSupportedException e) {}
    139         return clone;
    140     }
    141 
    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 
    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      */
    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