使用GroupLayout在JPanel中将JLabel居中

Question

I am kind of frustrated with the group layout. How can I make it so that the label upLabel will be centered within the red upper panel?

This example is not working and I tried out a lot of things, so this was my last try before I kicked out the monitor out of the window ;-)

I know that there are better ways to center to text within the JPanel , but I just wanted to play around and wanted to understand the basics. I read to examples from oracle.com, but they are much more complex and honestly easier to understand. But this simple task isn't working for me.

Many greetings and thanks

import java.awt.Color;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.*;

public class Main1 extends JFrame{

public static void main(String[] args) {
    new Main1().begin();
}

public void begin() {
    try {
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

        setResizable(true);
        setSize(500, 500);
        setTitle("Hauptmenue");
        setLocationRelativeTo(null);
        setVisible(true);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

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

        layout.setAutoCreateGaps(true);
        layout.setAutoCreateContainerGaps(true);

        JPanel up = new JPanel();
        up.setBackground(Color.RED);
        JPanel mid = new JPanel();
        JPanel bot = new JPanel();

        // von links
        layout.setHorizontalGroup(layout.createParallelGroup().
                addComponent(up,300, 400, Short.MAX_VALUE).
                addComponent(mid).
                addComponent(bot));
        // von oben
        layout.setVerticalGroup(layout.createSequentialGroup().addComponent(up).
                addComponent(mid).
                addComponent(bot));

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

        JLabel upLabel = new JLabel("Dummy Text");

        layout.setHorizontalGroup(layout.createSequentialGroup().addComponent(upLabel, 300, 400, Short.MAX_VALUE));
        layout.setVerticalGroup(layout.createSequentialGroup().addComponent(upLabel));
    } catch (Exception e) {
        e.printStackTrace();
    }
}
}

Answer 1

For horizontal alignment, change:

JLabel upLabel = new JLabel("Dummy Text");

To:

JLabel upLabel = new JLabel("Dummy Text", SwingConstants.CENTER);