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      1 /*
      2  * Copyright (C) 2015 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 com.android.dialer.compat;
     18 
     19 import android.graphics.Path;
     20 import android.graphics.PathMeasure;
     21 import android.os.Build;
     22 import android.view.animation.Interpolator;
     23 import android.view.animation.PathInterpolator;
     24 
     25 public class PathInterpolatorCompat {
     26 
     27   public static Interpolator create(
     28       float controlX1, float controlY1, float controlX2, float controlY2) {
     29     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
     30       return new PathInterpolator(controlX1, controlY1, controlX2, controlY2);
     31     }
     32     return new PathInterpolatorBase(controlX1, controlY1, controlX2, controlY2);
     33   }
     34 
     35   private static class PathInterpolatorBase implements Interpolator {
     36 
     37     /** Governs the accuracy of the approximation of the {@link Path}. */
     38     private static final float PRECISION = 0.002f;
     39 
     40     private final float[] mX;
     41     private final float[] mY;
     42 
     43     public PathInterpolatorBase(Path path) {
     44       final PathMeasure pathMeasure = new PathMeasure(path, false /* forceClosed */);
     45 
     46       final float pathLength = pathMeasure.getLength();
     47       final int numPoints = (int) (pathLength / PRECISION) + 1;
     48 
     49       mX = new float[numPoints];
     50       mY = new float[numPoints];
     51 
     52       final float[] position = new float[2];
     53       for (int i = 0; i < numPoints; ++i) {
     54         final float distance = (i * pathLength) / (numPoints - 1);
     55         pathMeasure.getPosTan(distance, position, null /* tangent */);
     56 
     57         mX[i] = position[0];
     58         mY[i] = position[1];
     59       }
     60     }
     61 
     62     public PathInterpolatorBase(float controlX, float controlY) {
     63       this(createQuad(controlX, controlY));
     64     }
     65 
     66     public PathInterpolatorBase(
     67         float controlX1, float controlY1, float controlX2, float controlY2) {
     68       this(createCubic(controlX1, controlY1, controlX2, controlY2));
     69     }
     70 
     71     private static Path createQuad(float controlX, float controlY) {
     72       final Path path = new Path();
     73       path.moveTo(0.0f, 0.0f);
     74       path.quadTo(controlX, controlY, 1.0f, 1.0f);
     75       return path;
     76     }
     77 
     78     private static Path createCubic(
     79         float controlX1, float controlY1, float controlX2, float controlY2) {
     80       final Path path = new Path();
     81       path.moveTo(0.0f, 0.0f);
     82       path.cubicTo(controlX1, controlY1, controlX2, controlY2, 1.0f, 1.0f);
     83       return path;
     84     }
     85 
     86     @Override
     87     public float getInterpolation(float t) {
     88       if (t <= 0.0f) {
     89         return 0.0f;
     90       } else if (t >= 1.0f) {
     91         return 1.0f;
     92       }
     93 
     94       // Do a binary search for the correct x to interpolate between.
     95       int startIndex = 0;
     96       int endIndex = mX.length - 1;
     97       while (endIndex - startIndex > 1) {
     98         int midIndex = (startIndex + endIndex) / 2;
     99         if (t < mX[midIndex]) {
    100           endIndex = midIndex;
    101         } else {
    102           startIndex = midIndex;
    103         }
    104       }
    105 
    106       final float xRange = mX[endIndex] - mX[startIndex];
    107       if (xRange == 0) {
    108         return mY[startIndex];
    109       }
    110 
    111       final float tInRange = t - mX[startIndex];
    112       final float fraction = tInRange / xRange;
    113 
    114       final float startY = mY[startIndex];
    115       final float endY = mY[endIndex];
    116 
    117       return startY + (fraction * (endY - startY));
    118     }
    119   }
    120 }
    121