Question

I’ve been trying to do this assignment and for it to work I need the event mousePressed to work but for some reason it’s not responding to the mouse. Its purpose is to paint another yellow circle when the mouse is pressed.

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;

public class CatchMonster extends JPanel
{
    private int height = 300;
    private int width = 600;
    private final int delay = 4001;

    private ImageIcon image;
    private Timer timer;
    private int x, y, moveX, moveY, xPoint, yPoint;

public CatchMonster() {

    DotListener dot = new DotListener();
    addMouseListener(dot);


    timer = new Timer(delay, new timerListener());
    x = 40;
    y = 40;

    moveX = moveY = 3;
    setPreferredSize(new Dimension(width, height));
    setBackground(Color.black);
    timer.start();

}

public void paintComponent(Graphics g) {
    super.paintComponents(g);
    g.setColor(Color.yellow);
    g.fillOval(x, y, 60, 60);
}

private class timerListener implements ActionListener 
{
    public void actionPerformed(ActionEvent e) {
        Random gn = new Random();
        x = gn.nextInt(width);
        y = gn.nextInt(height);

        repaint();
    }
    }

private class DotListener implements MouseListener
{
    public void mousePressed(MouseEvent event)
    {
        repaint();
    }

    @Override
    public void mouseClicked(MouseEvent event) {


    }

    @Override
    public void mouseEntered(MouseEvent event) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseExited(MouseEvent event) {
        // TODO Auto-generated method stub

    }

    @Override
    public void mouseReleased(MouseEvent event) {
        // TODO Auto-generated method stub

    }


}

}

Answer 1

I need the event mousePressed to work but for some reason it’s not responding to the mouse. Its purpose is to paint another yellow circle when the mouse is pressed.

But it won’t paint another circle as all it does is call repaint(), and how is that going to paint anything new? If you want it to create another circle, you’ll have to give it logic to do so. For instance, if you want to paint more than one yellow oval, you’ll want to create an ArrayList of Point objects and add a Point into that array list in the mousePressed method. Then in the paintComponent method, you can iterate through the array list, painting ovals for each Point it contains.

In addition, you want to change this:

   public void paintComponent(Graphics g) {
      super.paintComponents(g); // this is not the "super" method of paintComponent
      g.setColor(Color.yellow);
      g.fillOval(x, y, 60, 60);
   }

to this:

   public void paintComponent(Graphics g) {
      super.paintComponent(g); // See the difference?
      g.setColor(Color.yellow);
      g.fillOval(x, y, 60, 60);
   }

For example:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

public class CatchMonster extends JPanel {
   private int height = 300;
   private int width = 600;
   private final int delay = 4001;

   private ImageIcon image;
   private Timer timer;
   private int x, y, moveX, moveY, xPoint, yPoint;
   private List<Point> points = new ArrayList<Point>();

   public CatchMonster() {

      DotListener dot = new DotListener();
      addMouseListener(dot);

      timer = new Timer(delay, new timerListener());
      x = 40;
      y = 40;

      moveX = moveY = 3;
      setPreferredSize(new Dimension(width, height));
      setBackground(Color.black);
      timer.start();

   }

   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      g.setColor(Color.yellow);
      g.fillOval(x, y, 60, 60);

      int radius = 30;
      g.setColor(Color.green);
      for (Point p : points) {
         int x = p.x - radius;
         int y = p.y - radius;
         g.fillOval(x, y, 2 * radius, 2 * radius);
      }
   }

   private class timerListener implements ActionListener {
      public void actionPerformed(ActionEvent e) {
         Random gn = new Random();
         x = gn.nextInt(width);
         y = gn.nextInt(height);

         repaint();
      }
   }

   public static void main(String[] args) {
      JFrame frame = new JFrame("Foo");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new CatchMonster());
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   private class DotListener extends MouseAdapter {
      public void mousePressed(MouseEvent event) {
         points.add(event.getPoint());
         repaint();
      }

   }
}