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 
17 package com.android.internal.policy;
18 
19 import android.view.animation.Interpolator;
20 
21 /** @hide */
22 public class LogDecelerateInterpolator implements Interpolator {
23 
24     private int mBase;
25     private int mDrift;
26     private final float mLogScale;
27 
LogDecelerateInterpolator(int base, int drift)28     public LogDecelerateInterpolator(int base, int drift) {
29         mBase = base;
30         mDrift = drift;
31 
32         mLogScale = 1f / computeLog(1, mBase, mDrift);
33     }
34 
computeLog(float t, int base, int drift)35     private static float computeLog(float t, int base, int drift) {
36         return (float) -Math.pow(base, -t) + 1 + (drift * t);
37     }
38 
39     @Override
getInterpolation(float t)40     public float getInterpolation(float t) {
41         return computeLog(t, mBase, mDrift) * mLogScale;
42     }
43 }
44