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      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.tv.settings.widget;
     18 
     19 /**
     20  * Lerper model tracks target position by adding (target - source) / divisor to source position
     21  */
     22 public final class Lerper {
     23 
     24     public static final float DEFAULT_DIVISOR = 2.0f;
     25 
     26     private float mDivisor = DEFAULT_DIVISOR;
     27     private float mMinDelta = 1 / DEFAULT_DIVISOR;
     28 
     29     public void setDivisor(float divisor) {
     30         if (divisor < 1f) throw new IllegalArgumentException();
     31         mDivisor = divisor;
     32         mMinDelta = 1 / divisor;
     33     }
     34 
     35     public float getDivisor() {
     36         return mDivisor;
     37     }
     38 
     39     public float getMinDelta() {
     40         return mMinDelta;
     41     }
     42 
     43     public int getValue(int currentValue, int targetValue) {
     44         int delta = targetValue - currentValue;
     45         int retValue;
     46         if (delta > 0) {
     47             // make sure change currentValue and not exceeding targetValue
     48             delta = (int)(Math.ceil(delta / mDivisor));
     49             if (delta == 0) {
     50                 delta = 1;
     51             }
     52             retValue = currentValue + delta;
     53             if (retValue > targetValue) {
     54                 retValue = targetValue;
     55             }
     56         } else if (delta < 0) {
     57             // make sure change currentValue and not exceeding targetValue
     58             delta = (int)(Math.floor(delta / mDivisor));
     59             if (delta == 0) {
     60                 delta = -1;
     61             }
     62             retValue = currentValue + delta;
     63             if (retValue < targetValue) {
     64                 retValue = targetValue;
     65             }
     66         } else {
     67             retValue = targetValue;
     68         }
     69         return retValue;
     70     }
     71 
     72     public float getValue(float currentValue, float targetValue) {
     73         float delta = targetValue - currentValue;
     74         float retValue;
     75         if (delta > mMinDelta) {
     76             // make sure change currentValue and not exceeding targetValue
     77             delta = delta / mDivisor;
     78             retValue = currentValue + delta;
     79             if (retValue > targetValue) {
     80                 retValue = targetValue;
     81             }
     82         } else if (delta < -mMinDelta) {
     83             // make sure change currentValue and not exceeding targetValue
     84             delta = delta / mDivisor;
     85             retValue = currentValue + delta;
     86             if (retValue < targetValue) {
     87                 retValue = targetValue;
     88             }
     89         } else {
     90             retValue = targetValue;
     91         }
     92         return retValue;
     93     }
     94 }
     95