Mouse Clicks not registering correctly on JPanel

[Faz Ali]

Hi all,

I've just had my first dab in Java 2d graphics and have created a quick and rather crude program which draws a line between two points. The problem I am experiencing is that a lot of the mouse clicks just do not register on the JPanel. Any idea how to fix this? My code is below:

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

public class HangmanLabel extends JLabel implements MouseListener
{
	int[] locations = new int[4];
	int clickCounter = 0;

	public void paintComponent(Graphics g)
	{
		//Graphics2D graphics = (Graphics2D)g;
		g.setColor(Color.RED);
		g.drawLine(locations[0], locations[1], locations[2], locations[3]);
	}

	public void mouseClicked(MouseEvent e)
	{
		clickCounter++;
		System.out.println(clickCounter);
		if(clickCounter == 1)
		{
			
			locations[0] = e.getX();
			locations[1] = e.getY();
		}
	
		if(clickCounter == 2)
		{
			locations[2] = e.getX();
			locations[3] = e.getY();
			clickCounter = 0;
			this.repaint();
			this.validate();
		}
	}
	
	public void mouseEntered(MouseEvent e) {}

	public void mouseExited(MouseEvent e) {}

	public void mousePressed(MouseEvent e) {}

	public void mouseReleased(MouseEvent e) {}
	
	
	public static void main(String[] args)
	{
		HangmanLabel canvas = new HangmanLabel();
		canvas.addMouseListener(canvas);
		JFrame frame = new JFrame("Testing");
		frame.setSize(400,400);
		frame.getContentPane().add(canvas);
		frame.setVisible(true);
	}
}

[Ulf Dittmer]

Seems to work fine for me. What, exactly, are you experiencing?

[Rob Spoor]

And you forgot to call super.paintComponent(g) in your paintComponent method.

[Faz Ali]

Ulf Dittmer wrote:Seems to work fine for me. What, exactly, are you experiencing?

Sometimes the mouse clicks just do not register. I added System.out.println(clickCounter); in the code to detect when they are registered and sometimes I am definitely clicking the panel but it just doesn't register. There's no other way for we to describe what's happening.

[Faz Ali]

Rob Spoor wrote:And you forgot to call super.paintComponent(g) in your paintComponent method.

Why may I ask. - I haven't read that far ahead so maybe it's something that will come up but if you could explain it now, that would be great

[Darryl Burke]

Faz Ali wrote:Sometimes the mouse clicks just do not register.

A mouse click isn't trigerred if there's a movement in between mousePressed and mouseReleased.

[Rob Spoor]

Faz Ali wrote:

Rob Spoor wrote:And you forgot to call super.paintComponent(g) in your paintComponent method.

Why may I ask. - I haven't read that far ahead so maybe it's something that will come up but if you could explain it now, that would be great

super.paintComponent(g) makes sure the panel is drawn with a clean slate - all custom drawings will be removed. Currently, if the values in your locations array would change the repainting would only add the new locations, not remove the old ones.

[Faz Ali]

Rob Spoor wrote:

Faz Ali wrote:

Rob Spoor wrote:And you forgot to call super.paintComponent(g) in your paintComponent method.

Why may I ask. - I haven't read that far ahead so maybe it's something that will come up but if you could explain it now, that would be great

super.paintComponent(g) makes sure the panel is drawn with a clean slate - all custom drawings will be removed. Currently, if the values in your locations array would change the repainting would only add the new locations, not remove the old ones.

Hmm, that doesn't seem true. If you run the program you will see, it adds a new line whilst simultaneously removing the old line?