Now lets Swing

Lets look at a Swing application that does the same as above and a bit more:

Simple Swing Program Output

We have added three buttons that we will use to alter the look-and-feel of the Swing display.

The source code for this is as follows:

/*
 * ToolbarFrame2.java
 * The Swing-ified button example.  
 */

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

public class ToolbarFrame2 extends Frame implements ActionListener {

  // This time, let's use JButtons!
  JButton cutButton, copyButton, pasteButton;
  JButton winButton, javaButton, motifButton;

  public ToolbarFrame2() {
    super("Toolbar Example (Swing)");
    setSize(450, 250);
    addWindowListener(new BasicWindowMonitor());
  
    JPanel toolbar = new JPanel();
    toolbar.setLayout(new FlowLayout(FlowLayout.LEFT));

    cutButton = new JButton("Cut");
    cutButton.addActionListener(this);
    toolbar.add(cutButton);

    copyButton = new JButton("Copy");
    copyButton.addActionListener(this);
    toolbar.add(copyButton);

    pasteButton = new JButton("Paste");
    pasteButton.addActionListener(this);
    toolbar.add(pasteButton);

    add(toolbar, BorderLayout.NORTH);  // the new "preferred" BorderLayout add

    // Add the look and feel controls using regular AWT buttons
    JPanel lnfPanel = new JPanel();
    LnFListener lnfListener = new LnFListener(this);
    javaButton = new JButton("Metal");
    javaButton.addActionListener(lnfListener);
    lnfPanel.add(javaButton);
    motifButton = new JButton("Motif");
    motifButton.addActionListener(lnfListener);
    lnfPanel.add(motifButton);
    winButton = new JButton("Windows");
    winButton.addActionListener(lnfListener);
    lnfPanel.add(winButton);
    add(lnfPanel, BorderLayout.SOUTH);
  }

  public void actionPerformed(ActionEvent ae) {
    System.out.println(ae.getActionCommand());
  }

  public static void main(String args[]) {
    ToolbarFrame2 tf2 = new ToolbarFrame2();
    tf2.setVisible(true);
  }
}

The BasicWindowMonitor Class (above) is also required as is the LnFListener Class:

/*
 * LnFListener.java
 * A listener that can swing the look and feel of a frame based on
 * the actionCommand of an ActionEvent object.
 * Supported look and feels are:
 *  * Metal
 *  * Windows
 *  * Motif 
 */

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

public class LnFListener implements ActionListener {
  Frame frame;

  public LnFListener(Frame f) {
    frame = f;
  }

  public void actionPerformed(ActionEvent e) {
    String lnfName = null;

    if (e.getActionCommand().equals("Metal")) {
      lnfName = " javax.swing.plaf.metal.MetalLookAndFeel";
    } else if (e.getActionCommand().equals("Motif")) {
      lnfName = " com.sun.java.swing.plaf.motif.MotifLookAndFeel";
    } else {
      lnfName = " com.sun.java.swing.plaf.windows.WindowsLookAndFeel";
    }

    try {
      UIManager.setLookAndFeel(lnfName);
      SwingUtilities.updateComponentTreeUI(frame);
    }
    catch (UnsupportedLookAndFeelException ex1) {
      System.err.println("Unsupported LookAndFeel: " + lnfName);
    }
    catch (ClassNotFoundException ex2) {
      System.err.println("LookAndFeel class not found: " + lnfName);
    }
    catch (InstantiationException ex3) {
      System.err.println("Could not load LookAndFeel: " + lnfName);
    }
    catch (IllegalAccessException ex4) {
      System.err.println("Cannot use LookAndFeel: " + lnfName);
    }
  }
}

So What's New:

• First you must now include the new Swing Package:

  import javax.swing.*;

• Next the AWT Panel object is replaced by a Swing JPanel object.
• Also, all AWT Button objects are replaced by Swing JButton objects.
• Note a trend. Prefix AWT object with a J
• Not all changes from AWT to Swing are this simple -- for example Frames need a minor extension (see next Section) and others may need more extensions as we will see later.

We have also added the look-and-feel Buttons for Metal, Motif and Windows

• We change the look-and-feel in the LnFListener class
• This gets its events from the Appropriate buttons:

  // Add the look and feel controls 
     using regular AWT buttons
      JPanel lnfPanel = new JPanel();
      LnFListener lnfListener 
            = new LnFListener(this);
      javaButton = new JButton("Metal");
      javaButton.addActionListener(lnfListener);
      lnfPanel.add(javaButton);
  .....
  

• We figure out which button has been pressed in the actionPerformed(ActionEvent e) method by

  if (e.getActionCommand().equals("Metal"))
  

• We then set:

  lnfName = 
  " javax.swing.plaf.metal.MetalLookAndFeel";
  

  or com.sun.java.MotifLookAndFeel, com.sun.java.WindowsLookAndFeel as appropriate.

• To set the New look-and-feel is the simple:

        UIManager.setLookAndFeel(lnfName);
        SwingUtilities.updateComponentTreeUI(frame);
  

• The SwingUtilities.updateComponentTreeUI() call makes the change visible immediately.