Question

I have put some JPanels into another JPanel which its’ layout is Box Layout and Y-Axis.
After I have put all the panels I need to get the Y position of each added JPanel in from the JPanel container panel. But, when I try to get that I always get zero for Y position of each JPanel. Please tell me how to get the Y position of each Jpanel from the JPanel container JPanel.

This is what I have done,

JPanel panelHolder = new JPanel(new BoxLayout(this, BoxLayout.Y_AXIS));
for(int i = 0; i< 10; i++){
   JPanel p = new JPanel(); 
   panelHolder.add(p);
}

int componentCount = panelHolder.getComponentCount();

for (int j = 0; i < componentCount ; j++) {

  Component c = pnlRowHolder.getComponent(i);
  JPanel p = (JPanel)c;
  System.out.println(p.getY());//I get zero for all
}

Answer 1

Add your JPanel to the JFrames contentPane thus allowing you to get the X and Y co ordinates using getX() and get() though I’d suggest adding all components first, as the points may change as more components are added and then as trashgod said simply call pack() on the frame instance.

I did a short sample to demonstrate:

import java.awt.BorderLayout;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Test {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                new Test().createAndShowUI();
            }
        });
    }

    private void createAndShowUI() {
        JFrame frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        initComponents(frame);
        
        frame.pack();//call pack 
        
        printPanelCompPoints(mainPanel);//produces correct coords
        
        frame.setVisible(true);
    }
    
    private JPanel mainPanel;

    private void initComponents(JFrame frame) {
        mainPanel = new JPanel(new BorderLayout());
        JPanel centerPanel = new JPanel();
        JPanel northPanel = new JPanel();
        JPanel southPanel = new JPanel();
        JPanel westPanel = new JPanel();
        JPanel eastPanel = new JPanel();

        centerPanel.add(new JLabel("CENTER"));
        northPanel.add(new JLabel("NORTH"));
        eastPanel.add(new JLabel("EAST"));
        southPanel.add(new JLabel("SOUTH"));
        westPanel.add(new JLabel("WEST"));

        mainPanel.add(centerPanel, BorderLayout.CENTER);
        mainPanel.add(northPanel, BorderLayout.NORTH);
        mainPanel.add(southPanel, BorderLayout.SOUTH);
        mainPanel.add(eastPanel, BorderLayout.EAST);
        mainPanel.add(westPanel, BorderLayout.WEST);

       frame.getContentPane().add(mainPanel);
    
       printPanelCompPoints(mainPanel);//produces all 0's
    }

    private void printPanelCompPoints(JPanel mainPanel) {
        for (int i = 0; i < mainPanel.getComponentCount(); i++) {
            System.out.println(mainPanel.getComponent(i).getX() + ", " + mainPanel.getComponent(i).getY());
        }
    }
}

As you can see calling printPanelCompPoints(mainPanel); in initComponents(JFrame frame) produces all 0’s, (as they have been added to the frame but `pack() has not been called).

0, 0

0, 0

0, 0

0, 0

0, 0

however in the createAndShowUI() after calling pack() on the JFrames instance calling printPanelCompPoints(mainPanel); produces the correct co-odrinates:

44, 26

0, 0

0, 52

99, 26

0, 26