Question

I’m adding a panel into an already shown JFrame on click of button. Now when user resizes the frame, the panel remain constant at it’s location. What I want is panel location should also adjust as frame resizes. Any way to do that?

Code to regenerate my problem:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.GroupLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class ProblemPanelLocation {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                final JFrame frame = new JFrame("ProblemPanelLocation");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setSize(250, 250);
                final JPanel panel = new JPanel();
                panel.setSize(100, 100);
                panel.setBorder(BorderFactory.createBevelBorder(1));
                final JButton button = new JButton("Add panel");
                button.addActionListener(new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        panel.setLocation(button.getX() - button.getWidth() - 10, button.getY());
                        frame.getLayeredPane().add(panel, JLayeredPane.MODAL_LAYER);
                    }
                });
                GroupLayout layout = new GroupLayout(frame.getContentPane());
                frame.getContentPane().setLayout(layout);
                layout.setHorizontalGroup(
                    layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                    .addGroup(GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                        .addContainerGap(317, Short.MAX_VALUE)
                        .addComponent(button)
                        .addContainerGap())
                );
                layout.setVerticalGroup(
                    layout.createParallelGroup(GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
                        .addComponent(button)
                        .addContainerGap(266, Short.MAX_VALUE))
                );
                frame.setVisible(true);
            }
        });
    }
}

The scenario:

1. At first you see a frame with a button in it.
2. When you click on it a panel is added into frame, in frame’s layered pane.
3. Panel’s location is calculated based on button location.
4. Now when you resize frame, button also moves to be at the right side of the frame, but panel don’t.

I want to add panel in such a way that it acts like button for location. Is it possible? and if yes then how can I do it?

Answer 1

1. Use a ComponentListener:

   frame.addComponentListener( new ComponentAdapter() {
       @Override
       public void componentResized( ComponentEvent e ) {
           panel.setLocation(button.getX() - button.getWidth() - 10, button.getY());
       }
   } );
   

2. Override the setBounds() method of the frame and update the location there. This is not recommended since this code will execute in the same EventDispatcher-Event as the actual resize but it may help to avoid the sluggish repaint when using a component listener.