Java Swing, 2nd Edition

The JFrame Class

The most common Swing container for Java applications is the JFrame class. Like java.awt.Frame, JFrame provides a top-level window with a title, border, and other platform-specific adornments (e.g., minimize, maximize, and close buttons). Because it uses a JRootPane as its only child, working with a JFrame is slightly different than working with an AWT Frame. An empty JFrame is shown in Figure 8-9.

Figure 8-9. Empty JFrame instances on Unix, Mac, and Windows platforms

The primary difference is that calls to add( ) must be replaced with calls to getContentPane( ).add( ). In fact, the addImpl( ) method is implemented so that a call made directly to add( ) throws an Error. (The error message tells you not to call add( ) directly.)

Properties

JFrame defines the properties shown in Table 8-8. The accessibleContext property is as expected. ContentPane , glassPane, layeredPane, and JMenuBar are really properties of JRootPane (described earlier in the chapter). JFrame provides direct access to these panes, as required by the RootPaneContainer interface.

Table 8-8. JFrame properties

Property	Data type	get	is	set	Default value
accessibleContext o	AccessibleContext	·			JFrame.Accessible-JFrame( )
background o	Color	·		·	UIManager.getColor ("control")
contentPane o	Container	·		·	From rootPane
defaultCloseOperation	int	·		·	HIDE_ON_CLOSE
glassPane o	Component	·		·	From rootPane ...