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 17package android.support.v4.view.animation; 18 19import android.view.animation.Interpolator; 20 21/** 22 * An {@link Interpolator} that uses a lookup table to compute an interpolation based on a 23 * given input. 24 */ 25abstract class LookupTableInterpolator implements Interpolator { 26 27 private final float[] mValues; 28 private final float mStepSize; 29 30 public LookupTableInterpolator(float[] values) { 31 mValues = values; 32 mStepSize = 1f / (mValues.length - 1); 33 } 34 35 @Override 36 public float getInterpolation(float input) { 37 if (input >= 1.0f) { 38 return 1.0f; 39 } 40 if (input <= 0f) { 41 return 0f; 42 } 43 44 // Calculate index - We use min with length - 2 to avoid IndexOutOfBoundsException when 45 // we lerp (linearly interpolate) in the return statement 46 int position = Math.min((int) (input * (mValues.length - 1)), mValues.length - 2); 47 48 // Calculate values to account for small offsets as the lookup table has discrete values 49 float quantized = position * mStepSize; 50 float diff = input - quantized; 51 float weight = diff / mStepSize; 52 53 // Linearly interpolate between the table values 54 return mValues[position] + weight * (mValues[position + 1] - mValues[position]); 55 } 56 57} 58