Animating with Swing Timer

[Jj Hill]

I don't really know how to use javax.swing.timer in my application. My program animates a sprite moving across the screen to wherever you click, and it must look like it's traveling there. I used to use thread.sleep(), but that doesn't work anymore, so I've heard that I need to use javax.swing.timer. Here is my moveTo() method(I took the Thread.sleep() parts out):

public void moveTo(final int newX, final int newY, final int duration, final JPanel repaintPanel){
        animateTimer = new Timer(duration, animateListener);
        
        
        animateListener = new ActionListener(){
            public void actionPerformed(ActionEvent e){
            
            }};
            
                
                repaintPanel.repaint();
                double transfer = 0.0;
  
     
        
        
               
              
             
               
               double dx = newX - imgX; //distance x
               double dy = newY - imgY; //distance y
               
               if(imgX > newX - 100 && imgX < newX + 100){
                   
                  for(int i = imgX; i < 10000; i++){
                      if(newY > imgY) //if the destination Y is within 200 pixels, just add or subtract y, don't do anything with the x
                      imgY++;
                      if(newY < imgY)
                      imgY--;
                      if(imgY == newY){imgY = newY;}
                      
                  }
              }
               
               
               final double slope = dy / dx;
               
               
              
                  if(imgX < newX){
                    int i = imgX;
                    
                   
                   if(imgX == newX){imgX = newX;}
                   if(imgY == newY){imgY = newY;}
                   
                   
                   transfer = slope * i - slope * newX + newY; 
                   
                   
                   
                   
                   imgY = (int)transfer; //cast to int in the final step, not earlier
                  
               
                   imgX = i;
              
                  i++;
             
               
           } else if(imgX > newX) {
                      int i = imgX;
                       if(imgX == newX){imgX = newX;}
                   if(imgY == newY){imgY = newY;}
                   
                   
                   transfer = slope * i - slope * newX + newY; 
                   
                   
                   
                   
                   imgY = (int)transfer;//cast to int in the final step, not earlier
               
                   imgX = i;
                      
                      
                      
                      i--;
                      
                  }
        
        
   animateTimer.start();     
}     

I don't know how to insert the actionlistener. I have tried by myself but I can't seem to get it right. Btw, the moveTo method is called in a separate class, on the EDT.

[Michael Dunn]

the basic scenario with a swing timer is

you draw your image (via the container's paintComponent()) at x,y
in the timer, you change x,y and call [container].repaint()

[Randall Twede]

this isn't exactly the same thing, but it might give the answer you need.

/*
 * AnalogClock.java
 * Displays the current time on an old syle analog clock
 */

/**
 * Created 11/2011
 * By Randall Twede
 */

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Calendar;

public class AnalogClock extends JFrame implements ActionListener
{
    private Clock clock = new Clock();
    private Timer timer = new Timer(1000,this);
    private Image face = Toolkit.getDefaultToolkit().createImage("big-analog-clock.gif");
    private int second;	// the second
    private int minute;	// the minute
    private int hour;	// the hour
    private double secondAngle;	// the angle of the second hand
    private double minuteAngle;	// the angle of the minute hand
    private double hourAngle;	// the angle of the hour hand
    private final int secondLength = 160;	// the length of the second hand
    private final int minuteLength = 160;	// the length of the minute hand
    private final int hourLength = 120  ;		// the length of the hour hand
    private Point origin;

    public AnalogClock()
    {
        setTitle("AnalogClock");
        Container c = getContentPane();
	c.add(clock);
    }

    public void run()
    {
	origin = new Point(clock.getWidth()/2,clock.getHeight()/2);
	timer.start();
    }

    public void actionPerformed(ActionEvent e)
    {
	getTime();
	hourAngle = (Math.PI/2 - hour * (Math.PI / 6)) - minute * (Math.PI / 360);
	minuteAngle = Math.PI/2 - minute * (Math.PI / 30);
	secondAngle = Math.PI/2 - second * (Math.PI / 30);
	clock.repaint();
    }

    // centers a JFrame
    public void center()
    {
        this.setLocationRelativeTo(null);   
    }


    private void getTime()
    {
	Calendar now = Calendar.getInstance();
	hour = now.get(Calendar.HOUR);
	minute = now.get(Calendar.MINUTE);
	second = now.get(Calendar.SECOND);
    }

    class Clock extends JPanel
    {
    	public void paintComponent(Graphics g)
    	{
	    super.paintComponent(g);
	    g.drawImage(face, 0, 0, null);
	    g.drawLine(origin.x,origin.y,(int)(origin.x + Math.cos(hourAngle) * hourLength),(int)(origin.y - Math.sin(hourAngle) * hourLength));
	    g.drawLine(origin.x,origin.y,(int)(origin.x + Math.cos(minuteAngle) * minuteLength),(int)(origin.y - Math.sin(minuteAngle) * minuteLength));
	    g.setColor(Color.RED);
	    g.drawLine(origin.x,origin.y,(int)(origin.x + Math.cos(secondAngle) * secondLength),(int)(origin.y - Math.sin(secondAngle) * secondLength));
    	}
    }

    // create and display an instance of AnalogClock
    public static void main(String args[])
    {
        AnalogClock clock = new AnalogClock();
	clock.setSize(421, 443);
        clock.center();
        clock.setVisible(true);
        clock.setDefaultCloseOperation(EXIT_ON_CLOSE);
	clock.run();
    }
}

[Campbell Ritchie]

I am impressed by your mathematical abilities in that post

[Randall Twede]

lol Campbell.
i just wanted to mention that the timer can be started in the constructor. i had the run() method because i couldn't compute origin in my constructor. it seemed like a good place to start the timer.