How to overlay, resize and centre a component on a JPanel?

Question

I\'ve spent a while reading and experimenting here, and come up with a few approaches, but not got any of them to work completely yet, so I would like to know what more expe

Answer 1

I know this is a layout question, but SwingWorker might make the problem simpler if you have useful interim results. I sometimes start with this example.

Answer 2

The preferred size of JProgressBar is specified by the UI delegate, BasicProgressBarUI. The example below illustrates the effect of various layout managers. FlowLayout simply uses the UIManager default, ProgressBar.horizontalSize, while GridLayout and BorderLayout.CENTER fill the available space. BoxLayout, with flanking glue, adjusts proportionally as the frame is resized.

I am already using a SwingWorker

Updating the GUI from the process() method of your SwingWorker should be safe. You can change layers or even remove components, but I'd be wary of anything overly complicated.

Addendum: Here's the relevant default.

System.out.println(UIManager.get("ProgressBar.horizontalSize"));

javax.swing.plaf.DimensionUIResource[width=146,height=12]

Code:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.LayoutManager;
import javax.swing.BorderFactory;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;

/** @see http://stackoverflow.com/questions/7256775 */
public class ProgressTest {

    private static final Color border = Color.gray;

    private static void display() {
        JFrame f = new JFrame("ProgressTest");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLayout(new GridLayout(0, 1));
        f.add(createPanel(new FlowLayout()));
        f.add(createPanel(new GridLayout()));
        f.add(createPanel(new BorderLayout()));

        JPanel p = new JPanel();
        p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));
        p.setBorder(BorderFactory.createLineBorder(border));
        JProgressBar jpb = new JProgressBar();
        p.add(Box.createHorizontalGlue());
        p.add(jpb);
        p.add(Box.createHorizontalGlue());
        jpb.setIndeterminate(true);
        f.add(p);

        f.pack();
        f.setSize(320, 240);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static JPanel createPanel(LayoutManager layout) {
        JPanel p = new JPanel();
        p.setBorder(BorderFactory.createLineBorder(border));
        p.setLayout(layout);
        JProgressBar jpb = new JProgressBar();
        jpb.setIndeterminate(true);
        p.add(jpb);
        return p;
    }

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

            @Override
            public void run() {
                display();
            }
        });
    }
}