Swing Hacks

434

|

Chapter 11, Native Integration and Packaging

#86 Make Quick Look and Feel Changes

HACK

H A C K

#86

Make Quick Look and Feel Changes

Hack #86

Customize Metal with custom fonts, colors, and even system-bound

properties using just a few API calls.

Swing is a very customizable UI toolkit. The most advanced way of chang-

ing the look of your application is with a custom Look and Feel (L&F), but

they can be tricky to build. Swing’s L&F API is very complicated, often

requiring thousands of lines of code for a complete custom theme. Fortu-

nately, if you want to change just a few colors or fonts, the L&F API pro-

vides a much easier way. This hack shows how to create simple visual

changes using UI properties.

Look and Feel Properties

Every Look and Feel that extends the javax.swing.plaf.basic.* classes can

accept special properties that define the behavior of each Swing component.

For example, there is property to control the background color of every

JButton. If you change this property at the start of your program, then every

JButton you create will have that background color.

The UI properties are stored in a static class called the

UIManager. To set a

property, just put in the name of the property and a value object like a

Color. To set the background color of a button to green, you would do

something like this:

UIManager.put("Button.background", Color.green);

It is important to set these properties before any compo-

nents are created or they won’t pick up the new settings.

Below is the code for a simple program that shows a few components in a

frame. It has a button, label, and text field along the top and a text area in a

scroll pane in the middle. There is also a simple file menu at the top. Before

creating any components, it sets the foreground and background colors for

the button, label, text field, and panel to light and dark green:

public static void main(String[] args) throws Exception {

Color bg = Color.green.brighter( );

Color fg = Color.green.darker( );

UIManager.put("Button.background",bg);

UIManager.put("Button.foreground",fg);

Make Quick Look and Feel Changes #86

Chapter 11, Native Integration and Packaging

|

435

HACK

UIManager.put("Label.background",bg);

UIManager.put("Label.foreground",fg);

UIManager.put("TextField.background",bg);

UIManager.put("TextField.foreground",fg);

UIManager.put("Panel.background",bg);

UIManager.put("Panel.foreground",fg);

JTextArea jta = new JTextArea( );

jta.setText("text\ntext\ntext\ntext\ntext\ntext"+

"\ntext\ntext\ntext\ntext\ntext");

JScrollPane scroll = new JScrollPane(jta);

JButton button = new JButton("A Button");

JLabel label = new JLabel("A Label");

JTextField text = new JTextField("A TextField");

JMenuBar mb = new JMenuBar( );

JMenu file = new JMenu("File");

file.add(new JMenuItem("Open"));

file.add(new JMenuItem("Close"));

mb.add(file);

JFrame frame = new JFrame("Custom LaF Defaults");

JPanel top = new JPanel( );

top.setLayout(new BoxLayout(top,BoxLayout.X_AXIS));

top.add(button);

top.add(label);

top.add(text);

JPanel panel = new JPanel( );

panel.setLayout(new BorderLayout( ));

panel.add("North",top);

panel.add("Center",scroll);

frame.getContentPane( ).add(panel);

frame.setJMenuBar(mb);

frame.pack( );

frame.setSize(300,200);

frame.setVisible(true);

}

When compiled, this will look like Figure 11-11.

Swing provides over 300 properties that define the colors and fonts of each

standard component. This lets you customize almost anything in your pro-

gram. You can even set a color to be transparent, which may look interest-

ing if you have a pattern background.