Trying to change a JPanel's backcolor...

[b2271916]

I'm using Eclipse.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.border.BevelBorder;


public class mainForm extends JFrame {

	private JPanel contentPane;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					mainForm frame = new mainForm();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public mainForm() {
		setTitle("Test");
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 450, 300);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		contentPane.setLayout(null);
		
		 JPanel panel = new JPanel();
		panel.setBorder(new BevelBorder(BevelBorder.LOWERED, null, null, null, null));
		panel.addMouseListener(new MouseAdapter() {
			@Override
			public void mouseClicked(MouseEvent arg0) {
				panel.setBackground(Color.black);
			
			}
		});
		panel.setBounds(112, 62, 91, 72);
		contentPane.add(panel);
	}
}

On the line: "panel.setBackground(Color.black)", I'm getting the error: "Cannot refer to a non-final variable panel inside an inner class defined in a different method."

[Fubarable]

That error is correct: you cannot refer to a non-final local variable from within your anonymous MouseListener inner class. The reasons for this is due to the inner class making a local copy of the variable before using it, and if the variable is non-final then logic errors might occur. The simple solution: declare the panel JPanel variable final.

[b2271916]

How do I get all panels on the contentPane?
Current code is something like this:

for(int i=0;i<=contentPane.getComponentCount()-1;i++)
		{
					contentPane.getComponent(i).addMouseListener(ma);
		}

How do I check the type of the Component? I only want the MouseListener to be added to JPanels.

[PhHein]

Use instanceof to determine the type