javax.swing
Class JRootPane

java.lang.Object   
  java.awt.Component   
      java.awt.Container   
          javax.swing.JComponent   
              javax.swing.JRootPane

All Implemented Interfaces:

ImageObserver , MenuContainer , Serializable , Accessible

public class JRootPane
extends JComponent   
implements Accessible   

A lightweight container used behind the scenes by JFrame, JDialog, JWindow, JApplet, and JInternalFrame. For task-oriented information on functionality provided by root panes see How to Use Root Panes, a section in The Java Tutorial.

The following image shows the relationships between the classes that use root panes.

The "heavyweight" components (those that delegate to a peer, or native component on the host system) are shown with a darker, heavier box. The four heavyweight JFC/Swing containers (JFrame, JDialog, JWindow, and JApplet) are shown in relation to the AWT classes they extend. These four components are the only heavyweight containers in the Swing library. The lightweight container JInternalPane is also shown. All five of these JFC/Swing containers implement the RootPaneContainer interface, and they all delegate their operations to a JRootPane (shown with a little "handle" on top).

Note: The JComponent method getRootPane can be used to obtain the JRootPane that contains a given component.

The diagram at right shows the structure of a JRootPane. A JRootpane is made up of a glassPane, an optional menuBar, and a contentPane. (The JLayeredPane manages the menuBar and the contentPane.) The glassPane sits over the top of everything, where it is in a position to intercept mouse movements. Since the glassPane (like the contentPane) can be an arbitrary component, it is also possible to set up the glassPane for drawing. Lines and images on the glassPane can then range over the frames underneath without being limited by their boundaries.

Although the menuBar component is optional, the layeredPane, contentPane, and glassPane always exist. Attempting to set them to null generates an exception.

To add components to the JRootPane (other than the optional menu bar), you add the object to the contentPane of the JRootPane, like this:

       rootPane.getContentPane().add(child);
 

The same principle holds true for setting layout managers, removing components, listing children, etc. All these methods are invoked on the contentPane instead of on the JRootPane.

Note: The default layout manager for the contentPane is a BorderLayout manager. However, the JRootPane uses a custom LayoutManager. So, when you want to change the layout manager for the components you added to a JRootPane, be sure to use code like this:

    rootPane.getContentPane().setLayout(new BoxLayout());
 

If a JMenuBar component is set on the JRootPane, it is positioned along the upper edge of the frame. The contentPane is adjusted in location and size to fill the remaining area. (The JMenuBar and the contentPane are added to the layeredPane component at the JLayeredPane.FRAME_CONTENT_LAYER layer.)

The layeredPane is the parent of all children in the JRootPane -- both as the direct parent of the menu and the grandparent of all components added to the contentPane. It is an instance of JLayeredPane, which provides the ability to add components at several layers. This capability is very useful when working with menu popups, dialog boxes, and dragging -- situations in which you need to place a component on top of all other components in the pane.

The glassPane sits on top of all other components in the JRootPane. That provides a convenient place to draw above all other components, and makes it possible to intercept mouse events, which is useful both for dragging and for drawing. Developers can use setVisible on the glassPane to control when the glassPane displays over the other children. By default the glassPane is not visible.

The custom LayoutManager used by JRootPane ensures that:

1. The glassPane fills the entire viewable area of the JRootPane (bounds - insets).
2. The layeredPane fills the entire viewable area of the JRootPane. (bounds - insets)
3. The menuBar is positioned at the upper edge of the layeredPane.
4. The contentPane fills the entire viewable area, minus the menuBar, if present.

Any other views in the JRootPane view hierarchy are ignored.

If you replace the LayoutManager of the JRootPane, you are responsible for managing all of these views. So ordinarily you will want to be sure that you change the layout manager for the contentPane rather than for the JRootPane itself!

The painting architecture of Swing requires an opaque JComponent to exist in the containment hieararchy above all other components. This is typically provided by way of the content pane. If you replace the content pane, it is recommended that you make the content pane opaque by way of setOpaque(true). Additionally, if the content pane overrides paintComponent, it will need to completely fill in the background in an opaque color in paintComponent.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see XMLEncoder .

See Also:

JLayeredPane , JMenuBar , JWindow , JFrame , JDialog , JApplet , JInternalFrame , JComponent , BoxLayout , Mixing Heavy and Light Components, Serialized Form

Nested Class Summary

protected class	JRootPane.AccessibleJRootPane This class implements accessibility support for the JRootPane class.
protected class	JRootPane.RootLayout A custom layout manager that is responsible for the layout of layeredPane, glassPane, and menuBar.

Nested classes/interfaces inherited from class javax.swing.JComponent

JComponent.AccessibleJComponent

Nested classes/interfaces inherited from class java.awt.Container

Container.AccessibleAWTContainer

Nested classes/interfaces inherited from class java.awt.Component

Component.AccessibleAWTComponent , Component.BltBufferStrategy , Component.FlipBufferStrategy

Field Summary

static int	COLOR_CHOOSER_DIALOG Constant used for the windowDecorationStyle property.
protected Container	contentPane The content pane.
protected JButton	defaultButton The button that gets activated when the pane has the focus and a UI-specific action like pressing the Enter key occurs.
protected javax.swing.JRootPane.DefaultAction	defaultPressAction Deprecated. As of Java 2 platform v1.3.
protected javax.swing.JRootPane.DefaultAction	defaultReleaseAction Deprecated. As of Java 2 platform v1.3.
static int	ERROR_DIALOG Constant used for the windowDecorationStyle property.
static int	FILE_CHOOSER_DIALOG Constant used for the windowDecorationStyle property.
static int	FRAME Constant used for the windowDecorationStyle property.
protected Component	glassPane The glass pane that overlays the menu bar and content pane, so it can intercept mouse movements and such.
static int	INFORMATION_DIALOG Constant used for the windowDecorationStyle property.
protected JLayeredPane	layeredPane The layered pane that manages the menu bar and content pane.
protected JMenuBar	menuBar The menu bar.
static int	NONE Constant used for the windowDecorationStyle property.
static int	PLAIN_DIALOG Constant used for the windowDecorationStyle property.
static int	QUESTION_DIALOG Constant used for the windowDecorationStyle property.
static int	WARNING_DIALOG Constant used for the windowDecorationStyle property.

Fields inherited from class javax.swing.JComponent

accessibleContext , listenerList , TOOL_TIP_TEXT_KEY , ui , UNDEFINED_CONDITION , WHEN_ANCESTOR_OF_FOCUSED_COMPONENT , WHEN_FOCUSED , WHEN_IN_FOCUSED_WINDOW

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT , CENTER_ALIGNMENT , LEFT_ALIGNMENT , RIGHT_ALIGNMENT , TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT , ALLBITS , ERROR , FRAMEBITS , HEIGHT , PROPERTIES , SOMEBITS , WIDTH

Constructor Summary

JRootPane ()
Creates a JRootPane, setting up its glassPane, layeredPane, and contentPane.

Method Summary

protected void	addImpl (Component comp, Object constraints, int index) Overridden to enforce the position of the glass component as the zero child.
void	addNotify () Register ourselves with the SystemEventQueueUtils as a new root pane.
protected Container	createContentPane () Called by the constructor methods to create the default contentPane.
protected Component	createGlassPane () Called by the constructor methods to create the default glassPane.
protected JLayeredPane	createLayeredPane () Called by the constructor methods to create the default layeredPane.
protected LayoutManager	createRootLayout () Called by the constructor methods to create the default layoutManager.
AccessibleContext	getAccessibleContext () Gets the AccessibleContext associated with this JRootPane.
Container	getContentPane () Returns the content pane -- the container that holds the components parented by the root pane.
JButton	getDefaultButton () Returns the value of the defaultButton property.
Component	getGlassPane () Returns the current glass pane for this JRootPane.
JMenuBar	getJMenuBar () Returns the menu bar from the layered pane.
JLayeredPane	getLayeredPane () Gets the layered pane used by the root pane.
JMenuBar	getMenuBar () Deprecated. As of Swing version 1.0.3 replaced by getJMenubar().
RootPaneUI	getUI () Returns the L&F object that renders this component.
String	getUIClassID () Returns a string that specifies the name of the L&F class that renders this component.
int	getWindowDecorationStyle () Returns a constant identifying the type of Window decorations the JRootPane is providing.
boolean	isOptimizedDrawingEnabled () The glassPane and contentPane have the same bounds, which means JRootPane does not tiles its children and this should return false.
boolean	isValidateRoot () If a descendant of this JRootPane calls revalidate, validate from here on down.
protected String	paramString () Returns a string representation of this JRootPane.
void	removeNotify () Unregister ourselves from SystemEventQueueUtils.
void	setContentPane (Container content) Sets the content pane -- the container that holds the components parented by the root pane.
void	setDefaultButton (JButton defaultButton) Sets the defaultButton property, which determines the current default button for this JRootPane.
void	setGlassPane (Component glass) Sets a specified Component to be the glass pane for this root pane.
void	setJMenuBar (JMenuBar menu) Adds or changes the menu bar used in the layered pane.
void	setLayeredPane (JLayeredPane layered) Sets the layered pane for the root pane.
void	setMenuBar (JMenuBar menu) Deprecated. As of Swing version 1.0.3 replaced by setJMenuBar(JMenuBar menu).
void	setUI (RootPaneUI ui) Sets the L&F object that renders this component.
void	setWindowDecorationStyle (int windowDecorationStyle) Sets the type of Window decorations (such as borders, widgets for closing a Window, title ...) the JRootPane should provide.
void	updateUI () Resets the UI property to a value from the current look and feel.

Methods inherited from class javax.swing.JComponent

addAncestorListener , addVetoableChangeListener , computeVisibleRect , contains , createToolTip , disable , enable , firePropertyChange , firePropertyChange , firePropertyChange , fireVetoableChange , getActionForKeyStroke , getActionMap , getAlignmentX , getAlignmentY , getAncestorListeners , getAutoscrolls , getBorder , getBounds , getClientProperty , getComponentGraphics , getComponentPopupMenu , getConditionForKeyStroke , getDebugGraphicsOptions , getDefaultLocale