Core Swing Components - The Definitive Guide to Java Swing - page 102

JButton Properties
The JButton component doesn't add much to the AbstractButton . As Table 4-14 shows, of the
four properties of JButton , the only new behavior added is enabling the button to be the default.

Table 4-14. JButton Properties
Property Name

Data Type Access

accessibleContext AccessibleContext Read-only

defaultButton boolean

Read-only

defaultCapable boolean Read-write bound

UIClassID String Read-only

The default button tends to be drawn with a different and darker border than the remaining
buttons. When a button is the default, pressing the Enter key while in the top-level window
causes the button to be selected. This works only as long as the component with the input
focus, such as a text component or another button, doesn't consume the Enter key. Because
the defaultButton property is read-only, how (you might be asking) do you set a button as the
default? All top-level Swing windows contain a JRootPane , to be described in Chapter 8. You tell
this JRootPane which button is the default by setting its defaultButton property. Only buttons
whose defaultCapable property is true can be configured to be the default. Figure 4-13 shows
the top-right button set as the default.

Figure 4-13. Setting a default button

Listing 4-6 demonstrates setting the default button component, as well as using a basic
JButton . If the default button appearance doesn't seem that obvious in Figure 4-13, wait until
the JOptionPane is described in Chapter 9, where the difference in appearance will be more
obvious. Figure 4-13 uses a 2-by-2 GridLayout for the screen. The extra two arguments to the
constructor represent gaps to help make the default button's appearance more obvious.