actionbarsherlock/src/com/actionbarsherlock/internal/nineoldandroids/animation/FloatEvaluator.java

   1 /*
   2  * Copyright (C) 2010 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.actionbarsherlock.internal.nineoldandroids.animation;
  18
  19 /**
  20  * This evaluator can be used to perform type interpolation between <code>float</code> values.
  21  */
  22 public class FloatEvaluator implements TypeEvaluator<Number> {
  23
  24     /**
  25      * This function returns the result of linearly interpolating the start and end values, with
  26      * <code>fraction</code> representing the proportion between the start and end values. The
  27      * calculation is a simple parametric calculation: <code>result = x0 + t * (v1 - v0)</code>,
  28      * where <code>x0</code> is <code>startValue</code>, <code>x1</code> is <code>endValue</code>,
  29      * and <code>t</code> is <code>fraction</code>.
  30      *
  31      * @param fraction   The fraction from the starting to the ending values
  32      * @param startValue The start value; should be of type <code>float</code> or
  33      *                   <code>Float</code>
  34      * @param endValue   The end value; should be of type <code>float</code> or <code>Float</code>
  35      * @return A linear interpolation between the start and end values, given the
  36      *         <code>fraction</code> parameter.
  37      */
  38     public Float evaluate(float fraction, Number startValue, Number endValue) {
  39         float startFloat = startValue.floatValue();
  40         return startFloat + fraction * (endValue.floatValue() - startFloat);
  41     }
  42 }