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.wear.widget; 18 19import android.animation.TimeInterpolator; 20import android.annotation.TargetApi; 21import android.os.Build; 22import android.support.annotation.RestrictTo; 23import android.support.annotation.RestrictTo.Scope; 24 25/** 26 * Interpolator that uses a Bezier derived S shaped curve. 27 * 28 * @hide 29 */ 30@RestrictTo(Scope.LIBRARY_GROUP) 31@TargetApi(Build.VERSION_CODES.KITKAT_WATCH) 32class BezierSCurveInterpolator implements TimeInterpolator { 33 34 /** 35 * An instance of {@link BezierSCurveInterpolator}. 36 */ 37 public static final BezierSCurveInterpolator INSTANCE = new BezierSCurveInterpolator(); 38 /** 39 * Lookup table values. Generated using a Bezier curve from (0,0) to (1,1) with control points: 40 * P0 (0,0) P1 (0.4, 0) P2 (0.2, 1.0) P3 (1.0, 1.0) 41 * 42 * <p>Values sampled with x at regular intervals between 0 and 1. 43 */ 44 private static final float[] VALUES = new float[]{ 45 0.0f, 0.0002f, 0.0009f, 0.0019f, 0.0036f, 0.0059f, 0.0086f, 0.0119f, 0.0157f, 0.0209f, 46 0.0257f, 0.0321f, 0.0392f, 0.0469f, 0.0566f, 0.0656f, 0.0768f, 0.0887f, 0.1033f, 47 0.1186f, 0.1349f, 0.1519f, 0.1696f, 0.1928f, 0.2121f, 0.237f, 0.2627f, 0.2892f, 0.3109f, 48 0.3386f, 0.3667f, 0.3952f, 0.4241f, 0.4474f, 0.4766f, 0.5f, 0.5234f, 0.5468f, 0.5701f, 49 0.5933f, 0.6134f, 0.6333f, 0.6531f, 0.6698f, 0.6891f, 0.7054f, 0.7214f, 0.7346f, 50 0.7502f, 0.763f, 0.7756f, 0.7879f, 0.8f, 0.8107f, 0.8212f, 0.8326f, 0.8415f, 0.8503f, 51 0.8588f, 0.8672f, 0.8754f, 0.8833f, 0.8911f, 0.8977f, 0.9041f, 0.9113f, 0.9165f, 52 0.9232f, 0.9281f, 0.9328f, 0.9382f, 0.9434f, 0.9476f, 0.9518f, 0.9557f, 0.9596f, 53 0.9632f, 0.9662f, 0.9695f, 0.9722f, 0.9753f, 0.9777f, 0.9805f, 0.9826f, 0.9847f, 54 0.9866f, 0.9884f, 0.9901f, 0.9917f, 0.9931f, 0.9944f, 0.9955f, 0.9964f, 0.9973f, 55 0.9981f, 0.9986f, 0.9992f, 0.9995f, 0.9998f, 1.0f, 1.0f 56 }; 57 private static final float STEP_SIZE = 1.0f / (VALUES.length - 1); 58 59 /** 60 * To avoid users of this class creating multiple copies needlessly, the constructor is 61 * private. 62 */ 63 private BezierSCurveInterpolator() { 64 } 65 66 @Override 67 public float getInterpolation(float input) { 68 if (input >= 1.0f) { 69 return 1.0f; 70 } 71 72 if (input <= 0f) { 73 return 0f; 74 } 75 76 int position = Math.min((int) (input * (VALUES.length - 1)), VALUES.length - 2); 77 78 float quantized = position * STEP_SIZE; 79 float difference = input - quantized; 80 float weight = difference / STEP_SIZE; 81 82 return VALUES[position] + weight * (VALUES[position + 1] - VALUES[position]); 83 } 84} 85