Java Swing, 2nd Edition

The Root Pane

Now that we’ve seen the simplest example of a Swing container, we’ll move on to something a bit more powerful. Most of the other Swing containers (JFrame, JApplet, JWindow, JDialog, and even JInternalFrame) contain an instance of another class, JRootPane , as their only component, and implement a common interface, RootPaneContainer . In this section, we’ll look at JRootPane and RootPaneContainer, as well as another class JRootPane uses, JLayeredPane .

Before jumping into the descriptions of these classes, let’s take a look at how the classes and interfaces that make up the Swing root containers fit together. Figure 8-2 shows that JApplet, JFrame, JDialog, and JWindow do not extend JComponent as the other Swing components do. Instead, they extend their AWT counterparts, serving as top-level user interface windows. This implies that these components (unlike the lightweight Swing components) have native AWT peer objects.

Figure 8-2. Swing “root” container class diagram

Notice that these Swing containers (as well as JInternalFrame) implement a common interface, RootPaneContainer . This interface gives access to the JRootPane’s properties. Furthermore, each of the five containers uses a JRootPane as the “true” container of child components managed by the container. This class is discussed later in this chapter.

The JRootPane Class

JRootPane is a special container that extends ...