public interface RootPaneContainer
getContentPane() is generally implemented
 like this:
     public Container getContentPane() {
         return getRootPane().getContentPane();
     }
 
 This interface serves as a marker for Swing GUI builders
 that need to treat components like JFrame, that contain a
 single JRootPane, specially.  For example in a GUI builder,
 dropping a component on a RootPaneContainer would be interpreted
 as frame.getContentPane().add(child).
 
 As a convenience, the standard classes that implement this interface
 (such as JFrame, JDialog, JWindow, JApplet,
 and JInternalFrame) have their add, remove,
 and setLayout methods overridden, so that they delegate calls
 to the corresponding methods of the ContentPane.
 For example, you can add a child component to a frame as follows:
 
       frame.add(child);
 
 instead of:
 
       frame.getContentPane().add(child);
 
 
 The behavior of the add and
 setLayout methods for
 JFrame, JDialog, JWindow,
 JApplet and JInternalFrame is controlled by
 the rootPaneCheckingEnabled property. If this property is
 true (the default), then calls to these methods are
 forwarded to the contentPane; if false, these
 methods operate directly on the RootPaneContainer. This
 property is only intended for subclasses, and is therefore protected.
| Modifier and Type | Method and Description | 
|---|---|
| Container | getContentPane()Returns the contentPane. | 
| Component | getGlassPane()Returns the glassPane. | 
| JLayeredPane | getLayeredPane()Returns the layeredPane. | 
| JRootPane | getRootPane()Return this component's single JRootPane child. | 
| void | setContentPane(Container contentPane)The "contentPane" is the primary container for application
 specific components. | 
| void | setGlassPane(Component glassPane)The glassPane is always the first child of the rootPane
 and the rootPanes layout manager ensures that it's always
 as big as the rootPane. | 
| void | setLayeredPane(JLayeredPane layeredPane)A Container that manages the contentPane and in some cases a menu bar. | 
JRootPane getRootPane()
JRootPanevoid setContentPane(Container contentPane)
The contentPane may not be null.
 Generally implemented with
 getRootPane().setContentPane(contentPane);
contentPane - the Container to use for the contents of this
        JRootPaneIllegalComponentStateException - (a runtime
            exception) if the content pane parameter is nullJRootPane.getContentPane(), 
getContentPane()Container getContentPane()
setContentPane(java.awt.Container)void setLayeredPane(JLayeredPane layeredPane)
The layeredPane may not be null.
Generally implemented with
    getRootPane().setLayeredPane(layeredPane);IllegalComponentStateException - (a runtime
            exception) if the layered pane parameter is nullgetLayeredPane(), 
JRootPane.getLayeredPane()JLayeredPane getLayeredPane()
setLayeredPane(javax.swing.JLayeredPane)void setGlassPane(Component glassPane)
The glassPane may not be null.
 Generally implemented with
 getRootPane().setGlassPane(glassPane);
Component getGlassPane()
setGlassPane(java.awt.Component) Submit a bug or feature 
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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