Why the JProgressBar doesn't respect the setSize()?

问题

I'm having an issue with the JProgressBar, when it is printed in the GridBagLayout it is too little and the setSize method doesn't have effect, just to test I wrote 100 and 20 but the size remains something about 10x10 and I don't understand why, where is wrong? Thank you!

import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.RoundRectangle2D;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ProgressDialog {
    private final JDialog dialogFrame;
    private JProgressBar progressBar;

    public ProgressDialog() {

        dialogFrame = new JDialog();
        try {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException
                | UnsupportedLookAndFeelException ex) {
            System.err.println(ex.toString());
        }

        dialogFrame.setSize(200, 50);
        dialogFrame.setLayout(new GridBagLayout());

        GridBagConstraints constraints = new GridBagConstraints();

        constraints.gridx = 0;
        constraints.gridy = 0;
        constraints.weightx = 1.0;
        constraints.weighty = 1.0;
        constraints.insets = new Insets(5, 5, 5, 5);

        JLabel headingLabel = new JLabel("Caricamento...");
        Font f = headingLabel.getFont();
        f = new Font(f.getFontName(), Font.BOLD, f.getSize());
        headingLabel.setFont(f);
        headingLabel.setOpaque(false);
        dialogFrame.add(headingLabel, constraints);
        dialogFrame.setUndecorated(true);

        // Button
        constraints.gridx = 1;
        constraints.gridy = 0;
        constraints.weightx = 0;
        constraints.weighty = 0;

        JButton xButton = new JButton("X");
        xButton.setMargin(new Insets(1, 4, 1, 4));
        xButton.setFocusable(false);
        dialogFrame.add(xButton, constraints);

        // Progress bar
        constraints.gridx = 0;
        constraints.gridy = 1;
        constraints.weightx = 1.0;
        constraints.weighty = 1.0;
        constraints.gridwidth = 2;

        progressBar = new JProgressBar();
        progressBar.setMaximum(100);
        progressBar.setMinimum(0);
        progressBar.setSize(100, 20);
        progressBar.setStringPainted(true);
        progressBar.setBorderPainted(true);
        dialogFrame.add(progressBar, constraints);

        dialogFrame.setShape(new RoundRectangle2D.Double(1, 1, 200, 50, 20, 20));
        dialogFrame.setVisible(true);


        Dimension scrSize = Toolkit.getDefaultToolkit().getScreenSize();
        Insets toolHeight = Toolkit.getDefaultToolkit().getScreenInsets(dialogFrame.getGraphicsConfiguration());
        dialogFrame.setLocation(scrSize.width - 5 - dialogFrame.getWidth(), scrSize.height - 5 - toolHeight.bottom
                - dialogFrame.getHeight());

        xButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                dialogFrame.dispose();
            }
        });

    }

    public void destroy() {
        new Thread() {
            @Override
            public void run() {
                try {
                    Thread.sleep(500);
                    for (float i = 1.00f; i >= 0; i -= 0.01f) {
                        dialogFrame.setOpacity(i);
                        Thread.sleep(15);
                    }
                    dialogFrame.dispose();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            };
        }.start();

    }

    public void set(int n) {
        progressBar.setValue(n);
        progressBar.setString(n + "");
    }

    public static void main(String[] args) {
        new ProgressDialog();
    }

}

The main is to test it.

来源：https://stackoverflow.com/questions/29308336/why-the-jprogressbar-doesnt-respect-the-setsize