001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030/**
031 * 
032 */
033package org.openimaj.content.animation.animator;
034
035/**
036 *      An animator that will animate a value over a given time period. The animator
037 *      is constructed using a specific time period and on the first call of the
038 *      makeNextValue() will start a timer. 
039 *      <p>
040 *      Subclasses must implement a method that
041 *      can return a value based on an absolute percentage value. This class will 
042 *      convert the time each nextValue() is called into a percentage value between
043 *      the start and end times and use that to calculate the absolute value of
044 *      the animator.
045 *
046 *      @author David Dupplaw (dpd@ecs.soton.ac.uk)
047 *  @created 14 Aug 2012
048 *      @version $Author$, $Revision$, $Date$
049 *      @param <T> The type of value produced 
050 */
051public abstract class TimeBasedValueAnimator<T> implements ValueAnimator<T>
052{
053        /** The time the animation started */
054        private long startTime = 0;
055        
056        /** The length of the animation */
057        private long animationLength = 0;
058        
059        /** The start value of the animation */
060        protected T startValue = null;
061        
062        /** The end/target value of the animation */
063        protected T endValue = null;
064        
065        /** The current percentage */
066        private double currentPC = 0;
067        
068        /**
069         *      @param initial The start value for the animator
070         *      @param end The end value for the animator
071         *      @param millis The length of time the animation should run
072         */
073        public TimeBasedValueAnimator( final T initial, final T end, final long millis )
074        {
075                this.startValue = initial;
076                this.endValue = end;
077                this.animationLength = millis;
078        }
079
080        /**
081         *      Given a percentage value (0 < pc <=1), the method should return a value
082         *      for the animation.
083         * 
084         *      @param pc the percentage value
085         *      @return The animator value
086         */
087        protected abstract T calculateValue( double pc );
088
089        /**
090         *      {@inheritDoc}
091         *      @see org.openimaj.content.animation.animator.ValueAnimator#nextValue()
092         */
093        @Override
094        public T nextValue()
095        {               
096                final long currentTime = System.currentTimeMillis(); 
097                if( this.startTime == 0 )
098                        this.startTime = currentTime;
099                
100                this.currentPC = (currentTime - this.startTime) / (double)this.animationLength;
101
102                if( this.isComplete() ) return this.endValue;
103
104                return this.calculateValue( this.currentPC );
105        }
106
107        /**
108         *      {@inheritDoc}
109         *      @see org.openimaj.content.animation.animator.ValueAnimator#reset()
110         */
111        @Override
112        public void reset()
113        {
114                this.startTime = 0;
115                this.currentPC = 0;
116        }
117
118        /**
119         *      Returns whether the animator has completed
120         *      @return TRUE if the animator has completed.
121         */
122        public boolean isComplete()
123        {
124                return this.currentPC >= 1.0;
125        }
126
127        /**
128         *      A implementation sugar for {@link #isComplete()}
129         * 
130         *      {@inheritDoc}
131         *      @see org.openimaj.content.animation.animator.ValueAnimator#hasFinished()
132         */
133        @Override
134        public boolean hasFinished()
135        {
136                return this.isComplete();
137        }
138}