Java Swing

Addendum: Changes for Swing 1.1 Beta 3

Wouldn't you know it? Just when the three of us thought we released an up-to-date book and we're ready to sit back and give our hands a rest, JavaSoft goes and changes a bunch of things. Oh well.... I guess we're used to it by now, since Marc, Dave, and I have spent many sleepless nights updating Java Swing to cover the JDK 1.2 Beta 4 release. In any case, Sun has released a third beta for the Swing development libraries, so we thought we'd continue to bring you up to speed.

Swing 1.1 Beta 3

New Package Names

com.sun.java.swing.*

...in Beta 2 is now...

javax.swing.*

...in Beta 3. Again, let us mention that JavaSoft continues to allow you to download the Beta 2 libraries, which adhere to the old package name. However, you should strongly consider moving to the new. This means changing a ton of import statements at the front of your source files, and any fully qualified references to Swing classes that you may have lurking in your code. Luckily, JavaSoft now provides a tool that will help you make the transition with relative ease. It is called PackageRenamer, and you can download it from the JavaSoft PackageRenamer instruction page.

Faster Key Event Dispatching

Outline Dragging with Internal Frames

To activate this internal frame dragging, you can set the JDesktopPane.dragMode property to "outline," as shown below.

//  DragExample.java
//

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.border.*;

public class DragExample extends JFrame {

    JButton buttons[] = new JButton[100];

    public DragExample() {

        super("Focus Example");
        JPanel mypanel = new JPanel();
        mypanel.setLayout(new GridLayout(10,10));

        for (int i = 0; i < 100; i++) {
            buttons[i] = new JButton("Number " + i);
            mypanel.add(buttons[i]);
        }

        JInternalFrame frame1 = new JInternalFrame("Internal Frame 1",
                                                 true, true, true, true);

        frame1.setBackground(Color.lightGray);
        frame1.getContentPane().setLayout(new GridLayout(2, 3));
        frame1.setSize(200, 200);

        frame1.setContentPane(mypanel);

        JDesktopPane desktop = new JDesktopPane();
        desktop.add(frame1, new Integer(1));
        desktop.setOpaque(true);

        //  Here is the client property for XOR rectangle dragging
        desktop.putClientProperty("JDesktopPane.dragMode","outline");

        Container contentPane = getContentPane();
        contentPane.add(desktop, BorderLayout.CENTER);
        setSize(new Dimension(600, 400));
        setVisible(true);
    }

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

We should warn you that JavaSoft has provided this as only a short-term solution as of Beta 2, and a more comprehensive fix should be available in the future. Unfortunately, this change only covers moving the internal frame by dragging it via the title bar. Resizing the internal frame by grabbing any of the four corners still attempts to repaint the entire frame, despite the value of the JDesktopPane.dragMode client property. This remains true in Beta 3 as well.

Hue-Saturation-Brightness Panel in JColorChooser

//  ColorPick.java
//

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.colorchooser.*;

public class ColorPick extends JFrame {

    public static void main(String args[]) {
        ColorPick p = new ColorPick();
        JColorChooser chooser = new JColorChooser();
        Color c = chooser.showDialog(p, "Demo", Color.blue);
    }

}

A word of warning: the blended rectangle in the center of the dialog can take a few seconds to refresh, depending on the graphics capabilities of the machine and the OS. If you don't wish this panel to appear in the dialog, you can attempt to remove it using the appropriate methods of JColorChooser.

Additions to JEditorPane

    void setPage(java.net.URL url)
    void setPage(String s)

//  SimpleBrowser.java
//

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.swing.*;
import javax.swing.text.html.*;
import javax.swing.event.*;

public class SimpleBrowser extends JFrame {

    static JTextField textField;
    static JEditorPane editor;

    public SimpleBrowser(String s) {
        super(s);

        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());
        panel.setBorder(BorderFactory.createRaisedBevelBorder());

        editor = new JEditorPane();
        textField  = new JTextField();
        JScrollPane scrollPane = new JScrollPane(editor);

        editor.setEditable(false);

        panel.add(new JLabel("Location:  "), BorderLayout.WEST);
        panel.add(textField, BorderLayout.CENTER);

        getContentPane().add(panel, BorderLayout.NORTH);
        getContentPane().add(scrollPane, BorderLayout.CENTER);

        textField.addActionListener(new TextFieldListener());
    }

    public static void main(String args[]) {
        SimpleBrowser frame = new SimpleBrowser("Simple Browser");
        frame.setSize(400,400);
        frame.setVisible(true);
    }

    class TextFieldListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            try {
                editor.setPage(textField.getText());
            } catch (IOException ex) {
                editor.setText("Page could not be loaded");
            }
        }
    }
}

Not bad, huh? Kind of makes you want to just take a day off and write a browser. Again, be aware that the page will load asynchronously. If you want to type in a new URL before the first finishes loading, you can do that at any time. 

On a related note, limited support for character encodings has been added. This is important for documents which do not adhere to the standard character sets. Some of the other common character sets include ISO-8859-1, ISO-8859-5, Shift-jis, Euc-jp, and UTF-8. When a file is loaded that uses such a character set, its characters are converted to Unicode and processed normally. JavaSoft was not specific as to which character types it supported. However, when I tried it with Shift-jis, it threw an exception.

Finally, you can use the setContentType() method of JEditorPane to explicitly set the content type of a document. The prototype for the call looks like the following:

   public final void setContentType(String type)

• text/plain - ordinary text
• text/html - hypertext meta-language (HTML)
• text/rtf - rich text format

Calling this method is equivalent to calling both getEditorKitForContentType() and setEditorKit(). Note that you can specify the extra character set information in the URL of setPage() as well; JEditorPane will correctly parse the encoding information after the semicolon.

The HTML Package

You'll notice from our example above that we did not provide support for clicking on any links. Don't despair! This is also ridiculously simple! The key thing to remember here is that JEditorPane will generate hyperlink events if the editable property is set to false (i.e., setting JEditorPane.setEditable(false) )-  these events occur when the user clicks on a hyperlink in the text. With the added support for HotJava in the latest iteration of the javax.swing.text.html package, we can now provide more complete support for the JEditorPane "browser" that we defined above, including support for setting only the page inside the target HTML frame:

//  Browser.java
//

import java.awt.*;
import java.awt.event.*;
import java.io.*;

import javax.swing.*;
import javax.swing.text.html.*;
import javax.swing.event.*;

public class Browser extends JFrame {

    static JTextField textField;
    static JEditorPane editor;

    public Browser(String s) {
        super(s);

        JPanel panel = new JPanel();
        panel.setLayout(new BorderLayout());

        editor = new JEditorPane();
       textField  = new JTextField();
        JScrollPane scrollPane = new JScrollPane(editor);

        editor.setEditable(false);

        panel.add(new JLabel("Location:  "), BorderLayout.WEST);
        panel.add(textField, BorderLayout.CENTER);

        getContentPane().add(panel, BorderLayout.NORTH);
        getContentPane().add(scrollPane, BorderLayout.CENTER);

        editor.addHyperlinkListener(new HyperListener());
        textField.addActionListener(new TextFieldListener());
    }

    public static void main(String args[]) {
        Browser frame = new Browser("Browser");
        frame.setSize(400,400);
        frame.setVisible(true);
    }

    class HyperListener implements HyperlinkListener {

        public void hyperlinkUpdate(HyperlinkEvent e) {
            if (e.getEventType() == HyperlinkEvent.EventType.ACTIVATED) {
                JEditorPane sourcePane = (JEditorPane) e.getSource();
                if (e instanceof HTMLFrameHyperlinkEvent) {
                    HTMLFrameHyperlinkEvent event=(HTMLFrameHyperlinkEvent)e;
                    HTMLDocument doc=(HTMLDocument)sourcePane.getDocument();
                    doc.processHTMLFrameHyperlinkEvent(event);
                } else {
                    try {
                        textField.setText("Contacting " +
                            e.getURL().toString() + " ...");
                        sourcePane.setPage(e.getURL());
                        textField.setText(e.getURL().toString());
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }
    }

    class TextFieldListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            try {
                editor.setPage(textField.getText());
            } catch (IOException ex) {
                editor.setText("Page could not be loaded");
            }
        }
    }
}

Alas, we confess, we lifted the HyperListener class almost directly from the examples given with the package. However, it does demonstrate that working with the new HTML package is not only easy, but also is kind of fun. Here is an example page with tables from the Javadocs of the Swing Beta 3 libraries themselves:

Tables

• JTable.AUTO_RESIZE_SUBSEQUENT_COLUMNS-- resize only this column and each of the following columns to support the new size.
• JTable.AUTO_RESIZE_NEXT_COLUMN-- resize only this column and the following columns to support the new size.

Note that these constants regulate how the table will be sized when the auto-resizing is activated (e.g., there has been no call setAutoResizeMode(AUTO_RESIZE_OFF);  ). For example, here is example source code that presents a simple table. To resize the columns, drag along the walls of the headers at the top:

//  SimpleTable.java
//

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

public class SimpleTable extends JFrame {

  public SimpleTable() {
    super("Simple JTable");

    JTable jt = new JTable(new String[][] {
                               {"AAA", "BBB", "CCC", "DDD"},
                               {"EEE", "FFF", "GGG", "HHH"} },
                  new String[] {"Header1", "Header2",
                                "Header3", "Header4"} );

    jt.setAutoResizeMode(JTable.AUTO_RESIZE_NEXT_COLUMN);

    JScrollPane jsp = new JScrollPane(jt);
    setContentPane(jsp);
  }

  public static void main(String args[]) {
    SimpleTable st = new SimpleTable();
    st.setSize(300, 100);
    st.setVisible(true);
  }
}

First, try enlarging the "Header 1" column by placing the cursor on the border of "Header 1" and "Header 2" and dragging to the right. Note that both headers resize themselves to support the change.

Next, delete the line...

    jt.setAutoResizeMode(JTable.AUTO_RESIZE_NEXT_COLUMN);

    jt.setAutoResizeMode(JTable.AUTO_RESIZE_SUBSEQUENT_COLUMNS);

Support for these resizing policies has resulted in a new field in the TableColumn class to maintain the preferred width of the column; you probably won't need to worry about this. However, when you're working with tables, it is recommended that you use the setPreferredWidth() method instead of the setWidth() to set the default width of each of the table columns (you can get each of the columns with JTable's getColumn() method), as the latter approach is now deprecated. The preferred width of the column does not change if the table is reduced in size such that each column falls below its preferred width.

Text Package

If you're familiar with how the emacs text editor works, you'll be glad to know that the default text storage mechanism is now a class called GapContent. This class provides a more simplistic approach to working with a document by providing a "gap" in the Unicode which forms a smaller buffer by which changes to the text can be made. Again, this is an underlying class which most programmers will not need to be familiar with.

Localization

Internet Explorer 4.0

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