Aligning GroupLayout in the center of screen in Java Swing?

Question

So if i have a GUI like this:

import javax.swing.GroupLayout;
public class MyTest extends javax.swing.JFrame {

    public MyTest() {
        initComponents();
    }

    private void initComponents() {

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("This is a sample GUI");

        GroupLayout layout = new GroupLayout(getContentPane());
        getContentPane().setLayout(layout);

        layout.setHorizontalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGap(0, 244, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGap(0, 85, Short.MAX_VALUE)
        );

        pack();
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MyTest().setVisible(true);
            }
        });
    }   
}

Now when i run the program, it is aligned to (0,0) position on the top-left of the screen. Is there anyway i can align this to the center of the screen or to another custom position?
This works fine if i only use a frame without using GroupLayout, like with setLocation(left,top), but with this implementation, how can i change the default positioning of this GUI?

Answer 1

I guess you did answer the question but it wasn't that clear to me, regarding how to use it. Simply by calling below before pack(); was exactly what i was looking for:

this.setLocation(500,300); //value left, top in pixes
pack();  

So basically what i needed to know was the exact use of setLocation(x,y); and that with the use of keyword "this", thank you.

Answer 2

Put the contianer with a GroupLayout as the single component of a GridBagLayout with no constraint. The entire container will be centered.

---

i just need to center the whole GUI (with everthing in it) to the center of the scree,

That has nothing to do with GroupLayout and everything to do with setLocationRelativeTo(null). But read How to best position Swing GUIs for an even better way to position a GUI on-screen (i.e. at a more sensible place than the center of the screen - example below).

Answer 3

Like I mentioned in your earlier question, before I thought you were referring to centering the frame itself - use a GridBagLayout with no constraint. That will have the effect of putting the component in the center of the parent container. Note that since a frame has window decorations, that means the 'parent container' itself is slightly below screen center. If that is a problem, the only 'fix' I can think of is to use an undecorated frame.

I put 'fix' in inverted commas, because I think it is the requirement that is broken.

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

public class MyTest extends JFrame {

    public MyTest() {
        initComponents();
    }

    private void initComponents() {

        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setTitle("This is a sample GUI");
        getContentPane().setLayout(new GridBagLayout());

        JPanel gui = new JPanel();
        gui.setBackground(Color.GREEN);

        GroupLayout layout = new GroupLayout(gui);
        gui.setLayout(layout);

        layout.setHorizontalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGap(0, 244, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(GroupLayout.Alignment.LEADING)
            .addGap(0, 85, Short.MAX_VALUE)
        );

        add(gui);

        pack();
        setExtendedState(Frame.MAXIMIZED_BOTH );
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new MyTest().setVisible(true);
            }
        });
    }
}