001 package examples.moveongrid;
002
003 import java.awt.geom.*;
004 import fang.TrackerAdapter;
005
006 /**Moves a sprite smoothly over
007 * a set of cells in a given
008 * period of time.
009 * @author Jam Jenkins
010 */
011 public class GridTracker
012 extends TrackerAdapter
013 {
014 /**the number of vertical cells*/
015 private int rows;
016
017 /**the number of horizontal cells*/
018 private int columns;
019
020 /**the time remaining to move*/
021 private double timeLeft=0;
022
023 /**the total time given to move*/
024 private double totalTime=1;
025
026 /**the total distance required to move*/
027 private Point2D.Double totalDistance;
028
029 /**how far to move at this frame*/
030 private Point2D.Double translate;
031
032 /**makes a grid tracker to work on
033 * a square screen split up into the
034 * given number of rows and columns.
035 * @param rows the number of horizontal
036 * divisions in the screen
037 * @param columns the number of vertical
038 * divisions in the screen
039 */
040 public GridTracker(int rows, int columns)
041 {
042 this.rows=rows;
043 this.columns=columns;
044 totalDistance=new Point2D.Double();
045 translate=new Point2D.Double();
046 }
047
048 /**sets the time given to move from
049 * one cell to another
050 * @param totalTime the time in seconds
051 */
052 public void setMoveTime(double totalTime)
053 {
054 this.totalTime=totalTime;
055 }
056
057 /**moves a given number of cells up/down
058 * and left/right. The parameters represent
059 * the distance to move, not the target cell.
060 * If a move is currently underway, this
061 * method call returns immediately with no
062 * action taken and the call is ignored.
063 * @param r the number of cells to move
064 * vertically. Positive means move to the
065 * right and negative means move to the left.
066 * @param c the number of cells to move
067 * horizontally. Positive means move down
068 * and negative means move up.
069 */
070 public void move(int r, int c)
071 {
072 if(timeLeft>0)
073 return;
074 totalDistance.x=c/(double)columns;
075 totalDistance.y=r/(double)rows;
076 timeLeft=totalTime;
077 }
078
079 /**gets the translation amount
080 * @return the amount to move at this frame
081 */
082 public Point2D.Double getTranslation()
083 {
084 return translate;
085 }
086
087 /**updates the amount to translate
088 * given the amount of time that has
089 * passed.
090 * @param time the time since the last
091 * advanced time in seconds
092 */
093 public void advanceTime(double time)
094 {
095 if(timeLeft>0)
096 {
097 double timePassed=Math.min(timeLeft, time);
098 translate.x=totalDistance.x*timePassed/totalTime;
099 translate.y=totalDistance.y*timePassed/totalTime;
100 timeLeft-=timePassed;
101 }
102 else
103 {
104 translate.x=0;
105 translate.y=0;
106 }
107 }
108 }
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