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JRootPane.javaAPI DocJava SE 6 API40901Tue Jun 10 00:26:38 BST 2008javax.swing

JRootPane

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 following text describes this graphic.

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 JInternalFrame 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 following text describes this graphic.
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: Swing is not thread safe. For more information see Swing's Threading Policy.

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 {@link java.beans.XMLEncoder}.

see
JLayeredPane
see
JMenuBar
see
JWindow
see
JFrame
see
JDialog
see
JApplet
see
JInternalFrame
see
JComponent
see
BoxLayout
see
Mixing Heavy and Light Components
version
1.98 08/08/06
author
David Kloba

Fields Summary
private static final String
uiClassID
private static final boolean
LOG_DISABLE_TRUE_DOUBLE_BUFFERING
Whether or not we should dump the stack when true double buffering is disabled. Default is false.
private static final boolean
IGNORE_DISABLE_TRUE_DOUBLE_BUFFERING
Whether or not we should ignore requests to disable true double buffering. Default is false.
public static final int
NONE
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should not provide any sort of Window decorations.
public static final int
FRAME
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Frame.
public static final int
PLAIN_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog.
public static final int
INFORMATION_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to display an informational message.
public static final int
ERROR_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to display an error message.
public static final int
COLOR_CHOOSER_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to display a JColorChooser.
public static final int
FILE_CHOOSER_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to display a JFileChooser.
public static final int
QUESTION_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to present a question to the user.
public static final int
WARNING_DIALOG
Constant used for the windowDecorationStyle property. Indicates that the JRootPane should provide decorations appropriate for a Dialog used to display a warning message.
private int
windowDecorationStyle
protected JMenuBar
menuBar
The menu bar.
protected Container
contentPane
The content pane.
protected JLayeredPane
layeredPane
The layered pane that manages the menu bar and content pane.
protected Component
glassPane
The glass pane that overlays the menu bar and content pane, so it can intercept mouse movements and such.
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 DefaultAction
defaultPressAction
As of Java 2 platform v1.3 this unusable field is no longer used. To override the default button you should replace the Action in the JRootPane's ActionMap. Please refer to the key bindings specification for further details.
protected DefaultAction
defaultReleaseAction
As of Java 2 platform v1.3 this unusable field is no longer used. To override the default button you should replace the Action in the JRootPane's ActionMap. Please refer to the key bindings specification for further details.
boolean
useTrueDoubleBuffering
Whether or not true double buffering should be used. This is typically true, but may be set to false in special situations. For example, heavy weight popups (backed by a window) set this to false.
Constructors Summary
public JRootPane()
Creates a JRootPane, setting up its glassPane, layeredPane, and contentPane.


     
        LOG_DISABLE_TRUE_DOUBLE_BUFFERING = 
            AccessController.doPrivileged(new GetBooleanAction(
                                   "swing.logDoubleBufferingDisable"));
        IGNORE_DISABLE_TRUE_DOUBLE_BUFFERING =
            AccessController.doPrivileged(new GetBooleanAction(
                                   "swing.ignoreDoubleBufferingDisable"));
    
        setGlassPane(createGlassPane());
        setLayeredPane(createLayeredPane());
        setContentPane(createContentPane());
        setLayout(createRootLayout());
        setDoubleBuffered(true);
	updateUI();
Methods Summary
protected voidaddImpl(java.awt.Component comp, java.lang.Object constraints, int index)
Overridden to enforce the position of the glass component as the zero child.

param
comp the component to be enhanced
param
constraints the constraints to be respected
param
index the index

        super.addImpl(comp, constraints, index);
        
        /// We are making sure the glassPane is on top. 
        if(glassPane != null 
            && glassPane.getParent() == this
            && getComponent(0) != glassPane) {
            add(glassPane, 0);
        }
public voidaddNotify()
Register ourselves with the SystemEventQueueUtils as a new root pane.

	SystemEventQueueUtilities.addRunnableCanvas(this);
        super.addNotify();
        enableEvents(AWTEvent.KEY_EVENT_MASK);
protected java.awt.ContainercreateContentPane()
Called by the constructor methods to create the default contentPane. By default this method creates a new JComponent add sets a BorderLayout as its LayoutManager.

return
the default contentPane

        JComponent c = new JPanel();
        c.setName(this.getName()+".contentPane");
        c.setLayout(new BorderLayout() {
            /* This BorderLayout subclass maps a null constraint to CENTER.
             * Although the reference BorderLayout also does this, some VMs
             * throw an IllegalArgumentException.
             */
            public void addLayoutComponent(Component comp, Object constraints) {
                if (constraints == null) {
                    constraints = BorderLayout.CENTER;
                }
                super.addLayoutComponent(comp, constraints);
            }
        });
        return c;
protected java.awt.ComponentcreateGlassPane()
Called by the constructor methods to create the default glassPane. By default this method creates a new JComponent with visibility set to false.

return
the default glassPane

        JComponent c = new JPanel();
        c.setName(this.getName()+".glassPane");
        c.setVisible(false);
        ((JPanel)c).setOpaque(false);
        return c;
protected javax.swing.JLayeredPanecreateLayeredPane()
Called by the constructor methods to create the default layeredPane. Bt default it creates a new JLayeredPane.

return
the default layeredPane

        JLayeredPane p = new JLayeredPane();
        p.setName(this.getName()+".layeredPane");
        return p;
protected java.awt.LayoutManagercreateRootLayout()
Called by the constructor methods to create the default layoutManager.

return
the default layoutManager.

        return new RootLayout();
final voiddisableTrueDoubleBuffering()

        if (useTrueDoubleBuffering) {
            if (!IGNORE_DISABLE_TRUE_DOUBLE_BUFFERING) {
                if (LOG_DISABLE_TRUE_DOUBLE_BUFFERING) {
                    System.out.println("Disabling true double buffering for " +
                                       this);
                    Thread.dumpStack();
                }
                useTrueDoubleBuffering = false;
                RepaintManager.currentManager(this).
                        doubleBufferingChanged(this);
            }
        }
public javax.accessibility.AccessibleContextgetAccessibleContext()
Gets the AccessibleContext associated with this JRootPane. For root panes, the AccessibleContext takes the form of an AccessibleJRootPane. A new AccessibleJRootPane instance is created if necessary.

return
an AccessibleJRootPane that serves as the AccessibleContext of this JRootPane

        if (accessibleContext == null) {
            accessibleContext = new AccessibleJRootPane();
        }
        return accessibleContext;
public java.awt.ContainergetContentPane()
Returns the content pane -- the container that holds the components parented by the root pane.

return
the Container that holds the component-contents

 return contentPane;
public javax.swing.JButtongetDefaultButton()
Returns the value of the defaultButton property.

return
the JButton which is currently the default button
see
#setDefaultButton

 
        return defaultButton;
public java.awt.ComponentgetGlassPane()
Returns the current glass pane for this JRootPane.

return
the current glass pane
see
#setGlassPane

 
        return glassPane;
public javax.swing.JMenuBargetJMenuBar()
Returns the menu bar from the layered pane.

return
the JMenuBar used in the pane

 return menuBar;
public javax.swing.JLayeredPanegetLayeredPane()
Gets the layered pane used by the root pane. The layered pane typically holds a content pane and an optional JMenuBar.

return
the JLayeredPane currently in use

 return layeredPane;
public javax.swing.JMenuBargetMenuBar()
Returns the menu bar value.

deprecated
As of Swing version 1.0.3 replaced by getJMenuBar().
return
the JMenuBar used in the pane

 return menuBar;
public javax.swing.plaf.RootPaneUIgetUI()
Returns the L&F object that renders this component.

return
LabelUI object
since
1.3

        return (RootPaneUI)ui;
public java.lang.StringgetUIClassID()
Returns a string that specifies the name of the L&F class that renders this component.

return
the string "RootPaneUI"
see
JComponent#getUIClassID
see
UIDefaults#getUI

        return uiClassID;
final booleangetUseTrueDoubleBuffering()

        return useTrueDoubleBuffering;
public intgetWindowDecorationStyle()
Returns a constant identifying the type of Window decorations the JRootPane is providing.

return
One of NONE, FRAME, PLAIN_DIALOG, INFORMATION_DIALOG, ERROR_DIALOG, COLOR_CHOOSER_DIALOG, FILE_CHOOSER_DIALOG, QUESTION_DIALOG or WARNING_DIALOG.
see
#setWindowDecorationStyle
since
1.4

        return windowDecorationStyle;
public booleanisOptimizedDrawingEnabled()
The glassPane and contentPane have the same bounds, which means JRootPane does not tiles its children and this should return false. On the other hand, the glassPane is normally not visible, and so this can return true if the glassPane isn't visible. Therefore, the return value here depends upon the visiblity of the glassPane.

return
true if this component's children don't overlap

        return !glassPane.isVisible();
public booleanisValidateRoot()
If a descendant of this JRootPane calls revalidate, validate from here on down.

Deferred requests to layout a component and its descendents again. For example, calls to revalidate, are pushed upwards to either a JRootPane or a JScrollPane because both classes override isValidateRoot to return true.

see
JComponent#isValidateRoot
return
true

	return true;
protected java.lang.StringparamString()
Returns a string representation of this JRootPane. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

return
a string representation of this JRootPane.

	return super.paramString();
public voidremoveNotify()
Unregister ourselves from SystemEventQueueUtils.

see
#addNotify

	SystemEventQueueUtilities.removeRunnableCanvas(this);
        super.removeNotify();
public voidsetContentPane(java.awt.Container content)
Sets the content pane -- the container that holds the components parented by the root pane.

Swing's painting architecture requires an opaque JComponent in the containment hiearchy. This is typically provided by the content pane. If you replace the content pane it is recommended you replace it with an opaque JComponent.

param
content the Container to use for component-contents
exception
java.awt.IllegalComponentStateException (a runtime exception) if the content pane parameter is null

        if(content == null)
            throw new IllegalComponentStateException("contentPane cannot be set to null.");
        if(contentPane != null && contentPane.getParent() == layeredPane)
            layeredPane.remove(contentPane);
        contentPane = content;

        layeredPane.add(contentPane, JLayeredPane.FRAME_CONTENT_LAYER);
public voidsetDefaultButton(javax.swing.JButton defaultButton)
Sets the defaultButton property, which determines the current default button for this JRootPane. The default button is the button which will be activated when a UI-defined activation event (typically the Enter key) occurs in the root pane regardless of whether or not the button has keyboard focus (unless there is another component within the root pane which consumes the activation event, such as a JTextPane). For default activation to work, the button must be an enabled descendent of the root pane when activation occurs. To remove a default button from this root pane, set this property to null.

see
JButton#isDefaultButton
param
defaultButton the JButton which is to be the default button
beaninfo
description: The button activated by default in this root pane

 
        JButton oldDefault = this.defaultButton;

        if (oldDefault != defaultButton) {
            this.defaultButton = defaultButton;

            if (oldDefault != null) {
                oldDefault.repaint();
            }
            if (defaultButton != null) {
                defaultButton.repaint();
            } 
        }

        firePropertyChange("defaultButton", oldDefault, defaultButton);
public voidsetDoubleBuffered(boolean aFlag)
{@inheritDoc}

since
1.6

        if (isDoubleBuffered() != aFlag) {
            super.setDoubleBuffered(aFlag);
            RepaintManager.currentManager(this).doubleBufferingChanged(this);
        }
public voidsetGlassPane(java.awt.Component glass)
Sets a specified Component to be the glass pane for this root pane. The glass pane should normally be a lightweight, transparent component, because it will be made visible when ever the root pane needs to grab input events.

The new glass pane's visibility is changed to match that of the current glass pane. An implication of this is that care must be taken when you want to replace the glass pane and make it visible. Either of the following will work: 

root.setGlassPane(newGlassPane);
newGlassPane.setVisible(true);
or: 
root.getGlassPane().setVisible(true);
root.setGlassPane(newGlassPane);

param
glass the Component to use as the glass pane for this JRootPane
exception
NullPointerException if the glass parameter is null

        if (glass == null) {
            throw new NullPointerException("glassPane cannot be set to null.");
        }

        boolean visible = false;
        if (glassPane != null && glassPane.getParent() == this) {
            this.remove(glassPane);
            visible = glassPane.isVisible();
        }

        glass.setVisible(visible);
        glassPane = glass;
        this.add(glassPane, 0);
        if (visible) {
            repaint();
        }
public voidsetJMenuBar(javax.swing.JMenuBar menu)
Adds or changes the menu bar used in the layered pane.

param
menu the JMenuBar to add

        if(menuBar != null && menuBar.getParent() == layeredPane)
            layeredPane.remove(menuBar);
        menuBar = menu;

        if(menuBar != null)
            layeredPane.add(menuBar, JLayeredPane.FRAME_CONTENT_LAYER);
public voidsetLayeredPane(javax.swing.JLayeredPane layered)
Sets the layered pane for the root pane. The layered pane typically holds a content pane and an optional JMenuBar.

param
layered the JLayeredPane to use
exception
java.awt.IllegalComponentStateException (a runtime exception) if the layered pane parameter is null

        if(layered == null)
            throw new IllegalComponentStateException("layeredPane cannot be set to null.");
        if(layeredPane != null && layeredPane.getParent() == this)
            this.remove(layeredPane);
        layeredPane = layered;

        this.add(layeredPane, -1);
public voidsetMenuBar(javax.swing.JMenuBar menu)
Specifies the menu bar value.

deprecated
As of Swing version 1.0.3 replaced by setJMenuBar(JMenuBar menu).
param
menu the JMenuBar to add.

        if(menuBar != null && menuBar.getParent() == layeredPane)
            layeredPane.remove(menuBar);
        menuBar = menu;

        if(menuBar != null)
            layeredPane.add(menuBar, JLayeredPane.FRAME_CONTENT_LAYER);
public voidsetUI(javax.swing.plaf.RootPaneUI ui)
Sets the L&F object that renders this component.

param
ui the LabelUI L&F object
see
UIDefaults#getUI
beaninfo
bound: true hidden: true expert: true attribute: visualUpdate true description: The UI object that implements the Component's LookAndFeel.
since
1.3

        super.setUI(ui);
final voidsetUseTrueDoubleBuffering(boolean useTrueDoubleBuffering)

        this.useTrueDoubleBuffering = useTrueDoubleBuffering;
public voidsetWindowDecorationStyle(int windowDecorationStyle)
Sets the type of Window decorations (such as borders, widgets for closing a Window, title ...) the JRootPane should provide. The default is to provide no Window decorations (NONE).

This is only a hint, and some look and feels may not support this. This is a bound property.

param
windowDecorationStyle Constant identifying Window decorations to provide.
see
JDialog#setDefaultLookAndFeelDecorated
see
JFrame#setDefaultLookAndFeelDecorated
see
LookAndFeel#getSupportsWindowDecorations
throws
IllegalArgumentException if style is not one of: NONE, FRAME, PLAIN_DIALOG, INFORMATION_DIALOG, ERROR_DIALOG, COLOR_CHOOSER_DIALOG, FILE_CHOOSER_DIALOG, QUESTION_DIALOG, or WARNING_DIALOG.
since
1.4
beaninfo
bound: true enum: NONE JRootPane.NONE FRAME JRootPane.FRAME PLAIN_DIALOG JRootPane.PLAIN_DIALOG INFORMATION_DIALOG JRootPane.INFORMATION_DIALOG ERROR_DIALOG JRootPane.ERROR_DIALOG COLOR_CHOOSER_DIALOG JRootPane.COLOR_CHOOSER_DIALOG FILE_CHOOSER_DIALOG JRootPane.FILE_CHOOSER_DIALOG QUESTION_DIALOG JRootPane.QUESTION_DIALOG WARNING_DIALOG JRootPane.WARNING_DIALOG expert: true attribute: visualUpdate true description: Identifies the type of Window decorations to provide

        if (windowDecorationStyle < 0 ||
                  windowDecorationStyle > WARNING_DIALOG) {
            throw new IllegalArgumentException("Invalid decoration style");
        }
        int oldWindowDecorationStyle = getWindowDecorationStyle();
        this.windowDecorationStyle = windowDecorationStyle;
        firePropertyChange("windowDecorationStyle", 
                            oldWindowDecorationStyle,
                            windowDecorationStyle);
public voidupdateUI()
Resets the UI property to a value from the current look and feel.

see
JComponent#updateUI

        setUI((RootPaneUI)UIManager.getUI(this));