actionbarsherlock/src/com/actionbarsherlock/internal/nineoldandroids/animation/TypeEvaluator.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  * Interface for use with the {@link ValueAnimator#setEvaluator(TypeEvaluator)} function. Evaluators
  21  * allow developers to create animations on arbitrary property types, by allowing them to supply
  22  * custom evaulators for types that are not automatically understood and used by the animation
  23  * system.
  24  *
  25  * @see ValueAnimator#setEvaluator(TypeEvaluator)
  26  */
  27 public interface TypeEvaluator<T> {
  28
  29     /**
  30      * This function returns the result of linearly interpolating the start and end values, with
  31      * <code>fraction</code> representing the proportion between the start and end values. The
  32      * calculation is a simple parametric calculation: <code>result = x0 + t * (v1 - v0)</code>,
  33      * where <code>x0</code> is <code>startValue</code>, <code>x1</code> is <code>endValue</code>,
  34      * and <code>t</code> is <code>fraction</code>.
  35      *
  36      * @param fraction   The fraction from the starting to the ending values
  37      * @param startValue The start value.
  38      * @param endValue   The end value.
  39      * @return A linear interpolation between the start and end values, given the
  40      *         <code>fraction</code> parameter.
  41      */
  42     public T evaluate(float fraction, T startValue, T endValue);
  43
  44 }