Mouse event doesn't work in java for some reason

Question

Mouse event appears not to work, and i can't find out, why.
I added a debug output at imgEdit.drawDot and there's no output at the console. I'm a newbie in java, so my code may seem to be very bad, as well as my english

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
/**
 * Created by doctor on 12/29/15.
 */
public class MainUI {
 Window mainWindow;
 MainUI() {
 mainWindow = new Window();
 }
}
class Window extends JFrame {
 Window() {
 setBounds(0, 0, 600, 400);
 setTitle("RebBrush");
 Panel mainPanel = new Panel();
 Container mainCont = getContentPane();
 mainCont.setLayout(null);
 mainCont.add(mainPanel);
 setVisible(true);
 setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 }
}
class Panel extends JPanel {
 private ImageEdit imgEdit;
 private JLabel imgLabel;
 Panel() {
 setLayout(null);
 imgEdit = new ImageEdit(600, 400);
 imgLabel = new JLabel(new ImageIcon(imgEdit.getImage()));
 imgLabel.setBounds(0, 0, 600, 400);
 add(imgLabel);
 addMouseMotionListener(new MouseMotionListener() {
 @Override
 public void mouseDragged(MouseEvent e) {
 imgEdit.drawDot(e.getX(), e.getY());
 }
 @Override
 public void mouseMoved(MouseEvent e) {
 }
 });
 }
}

• StackFlowed: mouseDragged is when the button is kept clicked and the moved like a selection area.
• Peter Lawrey: Are you sure that changing the image which you used to create the ImageIcon will change anything on the screen?
• r3dm1ke: There's a debug output there, and that code area isn't even executed
• Arnaud: Shouldn't the MouseMotionListener be on the imgLabel ?
• Madhawa Priyashantha: do you see the mainPanel ?you are adding mainPanel to null layout and you haven't set bounds for it.use layout managers . set color to main panel and see where is it .mainPanel.setBackground(Color.yellow);

Answer 1

Simply getting rid of the null layouts did the trick for me. I'm not sure what ImageEdit is (some other class you've defined?), but by running the following I see "Mouse Dragged" show up in the console, so the mouseDragged method is definitely being called. Just uncomment the imageEdit stuff to put it back in.

import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
/**
 * Created by doctor on 12/29/15.
 */
public class MainUI {
 Window mainWindow;
 MainUI() {
 mainWindow = new Window();
 }
 public static void main(String[] args) {
 new MainUI();
 }
}
class Window extends JFrame {
 Window() {
 setBounds(0, 0, 600, 400);
 setTitle("RebBrush");
 Panel mainPanel = new Panel();
 Container mainCont = getContentPane();
 mainCont.add(mainPanel);
 setVisible(true);
 setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 }
}
class Panel extends JPanel {
 //private ImageEdit imgEdit;
 private JLabel imgLabel;
 Panel() {
 //imgEdit = new ImageEdit(600, 400);
 //imgLabel = new JLabel(new ImageIcon(imgEdit.getImage()));
 //imgLabel.setBounds(0, 0, 600, 400);
 //add(imgLabel);
 addMouseMotionListener(new MouseMotionListener() {
 @Override
 public void mouseDragged(MouseEvent e) {
 System.out.println("Mouse Dragged");
 //imgEdit.drawDot(e.getX(), e.getY());
 }
 @Override
 public void mouseMoved(MouseEvent e) {
 }
 });
 }
}