Resize JProgressBar if JFrame resizes

Question

I want to resize my JProgresbar when I resize my JFrame

the size of my JProgresBar is calculated like this:

progressBar.setPreferredSize(new Dimension(getWidth() - 100, 50));

but when I resize my JFrame the size of the progressbar will always stay the same.

UPDATE 1

This is my code:

public class MinimalExampleJProgresbar {
    public static void main(String[] args) {
        JFrame frame = new JFrame("SimpleFrame");
        JPanel jPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
        JProgressBar progressBar = new JProgressBar();

        jPanel.add(progressBar);
        frame.add(jPanel, BorderLayout.PAGE_START);

        frame.setExtendedState(Frame.MAXIMIZED_BOTH);
        frame.setVisible(true);
        progressBar.setPreferredSize(new Dimension(frame.getWidth() - 100, 50));
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    }
}

Answer 1

Use layout managers to your advantage. For example, a JFrame's contentPane uses BorderLayout. If you add your JProgressBar to this, to the BorderLayout.PAGE_END or the BorderLayout.PAGE_END position, it will automatically resize when its container resizes.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class SimpleFrame {
   private static void createAndShowGUI() {
      final JProgressBar progressBar = new JProgressBar(0, 100);
      progressBar.setBorder(BorderFactory.createTitledBorder("My Progress"));
      new Timer(200, new ActionListener() {
         int value = 0;

         @Override
         public void actionPerformed(ActionEvent e) {
            value += 10;
            if (value > 100) {
               value = 0;
            }
            progressBar.setValue(value);
         }
      }).start();


      JFrame frame = new JFrame("SimpleFrame");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.add(progressBar, BorderLayout.PAGE_START);
      frame.add(Box.createRigidArea(new Dimension(400, 300)));
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

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

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

public class MinimalExampleJProgresbar2 {
   public static void main(String[] args) {
       JFrame frame = new JFrame("SimpleFrame");
       JPanel wrapperPanel = new JPanel(new BorderLayout());

       JPanel jPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
       JProgressBar progressBar = new JProgressBar();

       wrapperPanel.add(progressBar, BorderLayout.PAGE_START);
       wrapperPanel.add(jPanel, BorderLayout.CENTER);

       frame.add(wrapperPanel, BorderLayout.PAGE_START);

       frame.setExtendedState(Frame.MAXIMIZED_BOTH);
       frame.setVisible(true);
       progressBar.setPreferredSize(new Dimension(frame.getWidth() - 100, 50));
       frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
   }
}

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;    
import javax.swing.*;

public class MinimalExampleJProgresbar2 {
   public static void main(String[] args) {
       JFrame frame = new JFrame("SimpleFrame");
       JPanel wrapperPanel = new JPanel(new BorderLayout());

       JPanel jPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
       final JProgressBar progressBar = new JProgressBar();

       new Timer(200, new ActionListener() {
          int value = 0;

          @Override
          public void actionPerformed(ActionEvent e) {
             value += 10;
             if (value > 100) {
                value = 0;
             }
             progressBar.setValue(value);
          }
       }).start();

       JPanel boxUser = new JPanel();
       boxUser.setLayout(new BoxLayout(boxUser, BoxLayout.LINE_AXIS));
       boxUser.add(Box.createHorizontalStrut(50));
       boxUser.add(progressBar);
       boxUser.add(Box.createHorizontalStrut(50));


       wrapperPanel.add(boxUser, BorderLayout.PAGE_START);
       wrapperPanel.add(jPanel, BorderLayout.CENTER);

       frame.add(wrapperPanel, BorderLayout.PAGE_START);

       frame.setExtendedState(Frame.MAXIMIZED_BOTH);
       frame.setVisible(true);
       frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
   }
}

Answer 2

Add a ComponentAdapter to your Frame

myFrame.addComponentListener(new ComponentAdapter() {
  public void componentResized(ComponentEvent ev) {
    progressBar.setPreferredSize(new Dimension(getWidth() - 100, 50));
    revalidate();
    repaint();
  }
});