定时器延迟问题Java

Question

I am trying to make a snake type game and I am having trouble making the "pellets" appear at random places at fixed intervals (I want to make it 10 seconds). When I run the program after the brief delay I gave it (1000 milliseconds) the pellets begin to appear extremely rapidly flashing on the screen in different locations. What I want to do is make the pellets appear one at a time in random locations every 10 seconds instead of flashing around rapidly. Any help would be appreciated.

PS I have never done something like this before so, apologies if the code may seem a bit crude. Any advice with coding in general is also very appreciated.

Edit: I know this is still incorrect but I just want to know if I am at least on the right track so far. Now the "pellet" is just sitting there in the top right hand corner of the frame. Is there a problem now with my timer or the list or just everything in general. By the way if updating my code just to show new problems is frowned upon in this website let me know and I'll just ask for help in the comments section and stop with the edits.

package snake;

import java.awt.* ;
import java.awt.event.*;
import java.util.* ;
import javax.swing.*;
import javax.swing.Timer;
/**
 *
 * @author Carlos
 */
public class Pellet extends JPanel
{
    Random randomNumber = new Random() ; 
    int x = 0 ;
    int y = 0 ;
    private Game game ;
    private Timer timer ;
    private final int DELAY = 100 ;
    private ArrayList<Pellet> al = new ArrayList<>() ;

    public Pellet(Game game)
    {        
        this.game = game ;        
    }

    @Override
    public void paint(Graphics g)
    {  
       super.paintComponent(g);
       g.fillOval(x, y, 10, 10);

       for(int i = 0 ; i < al.size() ; i++)
       {
           Pellet p = al.get(i) ;
           p.paintComponent(g);
       }

    }

    public void pelletTimer()
    {
        timer = new Timer(DELAY, new ActionListener()
        {
            public void actionPerformed(ActionEvent e)
            {
                x = randomNumber.nextInt(game.getWidth()) ;
                y = randomNumber.nextInt(game.getHeight()) ;
                Pellet p = new Pellet(game) ;
                al.add(p) ;
                repaint() ;
            }
        }) ;    
        timer.start();
    }


}

Answer 1

You've lots of issues with your code attempt, so let's try to go through them.

• First off this is a Swing program and so you must take care to not stomp on the Swing event thread, something that a java.util.Timer will do.
• You're also creating your java.util.Timer within a paint method, something that should never be done since this method is for painting and painting only, and should not be slowed down or involved with non-painting code.
• Your paint method is not a true paint method override of a Swing component since it has the wrong signature (it uses a Graphics2D parameter not the expected Graphics parameter) and your class does not extend a Swing component, so this method will do nothing of use for you.

Suggestions:

• Draw in a paintComponent method override in a class that extends JPanel.
• Call the super.paintComponent method first.
• Use a javax.swing.Timer or "Swing" Timer to drive your animation.
• In your Timer create a new pellet, add it to an ArrayList of pellets, and call repaint() which will tell the JVM to repaint your GUI and thus it will automatically call your paintComponent method for you.
• In your paintComponent method, after calling the super's method, iterate through the pellet ArrayList drawing each individual pellet as you do.
• Check out the Swing tutorials especially the graphics section. You can find a link to them here: swing info .
• And check out this site for Swing animation examples, many written by me. You can find some results with this search .