javax.swing
Class JRootPane

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JRootPane
All Implemented Interfaces:
Accessible, ImageObserver, MenuContainer, Serializable
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 JavaBeansTM 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

 

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 inherited from class javax.swing.JComponent
 
Nested classes inherited from class java.awt.Container
 
Nested classes inherited from class java.awt.Component
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, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getDefaultLocale, getGraphics, getHeight, getInputMap, getInputMap, getInputVerifier, getInsets, getInsets, getListeners, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFont, setForeground, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText,