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