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Trail: Creating a GUI with JFC/Swing
Lesson: Using Swing Components

Using HTML in Swing Components

Many Swing components display a text string as part of their GUI. By default, a component's text is displayed in a single font and color, all on one line. You can determine the font and color of a component's text by invoking the component's setFont and setForeground methods, respectively. For example, the following code creates a label and then sets its font and color: 
label = new JLabel("A label");
label.setFont(new Font("Serif", Font.PLAIN, 14));
label.setForeground(new Color(0xffffdd));
If you want to mix fonts or colors within the text, or to have formatting such as multiple lines, you can use HTML. HTML formatting can be used in all Swing buttons, menu items, labels, tool tips, and tabbed panes, as well as in components such as trees and tables that use labels as renderers.

To specify that a component's text has HTML formatting, just put the <html> tag at the beginning of the text, then use any valid HTML in the remainder. Here is an example of using HTML in a button's text: 

button = new JButton("<html><b><u>T</u>wo</b><br>lines</html>");
Here's the resulting button.

[PENDING: Figure: A button with HTML formatting]

Performance note: Because Swing's HTML rendering support uses many classes, users on older systems might notice a delay the first time a component with HTML formatting is shown. One way to avoid the possible delay is not to show the HTML-formatted component immediately, and to create it (or another component that uses HTML) on a background thread.

An Example: HtmlDemo

The following snapshot shows an application called HtmlDemo that lets you play with HTML formatting by setting the text on a label.

[PENDING: Figure: The HtmlDemo application]

Try This: 
  1. Run HtmlDemo using JavaTM Web Start (in the Creating a GUI with JFC/Swing trail). Or, to compile and run the example yourself, consult the example index.
  2. Edit the HTML in the text area at the left and click the "Change the label" button. The label at the right shows the result.
  3. Remove <html> from the text area on the left. The label's text is no longer parsed as HTML.

Example 2: ButtonHtmlDemo

Let's look at another example that uses HTML. ButtonHtmlDemo adds font, color, and other text formatting to three buttons. You can find its full source code in ButtonHtmlDemo.java (in a .java source file) and links to its image files in the example index. You can run ButtonHtmlDemo using Java Web Start (in the Creating a GUI with JFC/Swing trail).

[PENDING: Figure: The ButtonHtmlDemo application]

The left and right buttons have multiple lines and text styles and are implemented using HTML. The middle button, on the other hand, uses just one line, font, and color, so it doesn't require HTML. Here is the code that specifies the text formatting for these three buttons: 

b1 = new JButton("<html><center><b><u>D</u>isable</b><br>"
                 + "<font color=#ffffdd>middle button</font>",
                 leftButtonIcon);
Font font = b1.getFont().deriveFont(Font.PLAIN);
b1.setFont(font);
...
b2 = new JButton("middle button", middleButtonIcon);
b2.setFont(font);
b2.setForeground(new Color(0xffffdd));
...
b3 = new JButton("<html><center><b><u>E</u>nable</b><br>"
                 + "<font color=#ffffdd>middle button</font>",
                 rightButtonIcon);
b3.setFont(font);
Note that we had to use a <u> tag to cause the mnemonic characters "D" and "E" to be underlined in the HTML-using buttons. Note also that when a button is disabled, its HTML text unfortunately remains black, instead of becoming gray. (Keep an eye on bug #4783068 (outside of the tutorial) to see if this situation changes.)

This section discussed how to use HTML in ordinary, non-text components. For information on components whose primary purpose is formatting text, see Using Text Components (in the Creating a GUI with JFC/Swing trail).

Version note: HTML rendering in ordinary Swing components was first added in v 1.2.2 and completed in 1.3. The components that supported HTML in 1.2.2 were JButton, JLabel, JMenuItem, JMenu, JRadioButtonMenuItem, JCheckBoxMenuItem, JTabbedPane, and JToolTip. HTML support was added in 1.3 to JToggleButton, JCheckBox, and JRadioButton.

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