Swing Hacks

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Chapter 8, Rendering

#60 Changing Fonts Throughout Your Application

HACK

}

});

frame.getContentPane( ).add(button);

frame.pack( );

frame.setVisible(true);

}

And that’s it! Now you can add full-screen color choosing to any compo-

nent without requiring native access at all. As an improvement, you could

make the preview actually show a magnified view of where the cursor is

instead of just the selected color.

H A C K

#60

Changing Fonts Throughout Your Application Hack #60

Get a quick font face-lift, without having to write a whole Look and Feel.

With no standards documents to obey and more flexible user expectations,

web designers get much more freedom with their fonts than Swing develop-

ers expect. They get to set font styles with CSS, while we’re expected to just

leave well enough alone. Sure, you can change fonts on a component-by-

component basis with

setFont( ), but it’s not like you can just say “from

now on, I want all

JLabels to use the Cheese Deluxe Demi-Bold font.” Well,

OK, you could create a subclass of

JLabel to set that font in its constructor,

but your change wouldn’t be picked up by any of

JLabel’s subclasses, like

the default renderers for list, table, and tree cells. Fortunately, there is a

much easier way than fighting with single inheritance.

Swing components get many of their defaults (e.g., fonts, icons, borders),

from a

Hashtable owned by the UIManager class. Actually, it is a subclass of

Hashtable, called UIDefaults, which offers strongly typed methods like

getFont( ), getBorder( ), getColor( ), etc., each of which takes a key object.

Now, since this is just a

Hashtable, you can put stuff in just as easily as you

can get it out. All you have to do is know what the key is. As it turns out, for

fonts, the keys are

Strings that end with a .font suffix. So, for demonstra-

tion purposes, you can iterate through the keys of the

UIDefaults, and every

time you find one that ends in

.font, put the Font of your choice back into

the

UIDefaults.

Changing the Default Fonts

The goal of the ChangeAllFonts example is to change the default font of all

Swing components, by changing all the appropriate keys it can find in

UIDefaults. It starts by getting a font name from the command line and cre-

ating a 12-point plain

Font instance.

Changing Fonts Throughout Your Application #60

Chapter 8, Rendering

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305

HACK

Next, it gets the UIDefaults object as a Hashtable and gets an Enumeration of

its keys. It walks the enumeration and, for every key ending in

.font, it uses

put( )

to replace the previous font with the user-selected font.

Finally, it creates a simple GUI with several typical

JComponent

s and shows

them in a

JFrame

. This short example is shown in Example 8-7.

Example 8-7. Changing default fonts via UIDefaults

public class ChangeAllFonts {

final static String[] LIST_ITEMS =

{ "JList", "with", "new Font" };

public static void main (String[] args) {

try {

// get user's font

if (args.length < 1) {

System.out.println (

"Usage: ChangeAllFonts font-name");

return;

}

String fontName = args[0];

Font font = new Font (fontName, Font.PLAIN, 12);

// put this font in the defaults table for every

// ui font resource key

Hashtable defaults = UIManager.getDefaults( );

Enumeration keys = defaults.keys( );

while (keys.hasMoreElements( )) {

Object key = keys.nextElement( );

if ((key instanceof String) &&

(((String) key).endsWith(".font"))) {

System.out.println (key);

defaults.put (key, font);

}

}

// now bring up a GUI to show this off

JPanel panel = new JPanel( );

panel.setLayout (new BoxLayout (panel, BoxLayout.Y_AXIS));

panel.add (new JLabel ("JLabel with font " + fontName));

panel.add (new JTextField ("JTextField with font " +

fontName));

panel.add (new JButton ("JButton with font " +

fontName));

JList list = new JList (LIST_ITEMS);

JScrollPane pane =

new JScrollPane (list,

ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,

ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);

panel.add (pane);