javax.swing
Class JRootPane

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--javax.swing.JComponent
                    |
                    +--javax.swing.JRootPane

public class JRootPane

extends JComponent

implements Accessible

The fundamental component in the container hierarchy. In the same way that JComponent is fundamental to the JFC/Swing components, JRootPane is fundamental to the JFC/Swing window, frame, and pane containers. However, while other classes use inheritance to take advantage of JComponent's capabilities, the container classes delegate operations to a JRootPane instance. Those containers are the heavyweight containers: JFrame, JDialog, JWindow, and JApplet, as well as the lightweight container, JInternalFrame.

The following image shows these relationships:

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 5 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.

The contentPane must be the parent of any children of the JRootPane. Rather than adding directly to a JRootPane, like this:

       rootPane.add(child);
 

You instead add to the contentPane of the JRootPane, like this:

       rootPane.getContentPane().add(child);
 

The same priniciple 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. 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, if present, 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!

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. A future release of Swing will provide support for long term persistence.

See Also:

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

Inner Class Summary

protected class	JRootPane.AccessibleJRootPane The class used to obtain the accessible role for this object.
protected class	JRootPane.RootLayout A custom layout manager that is responsible for the layout of layeredPane, glassPane, and menuBar.

Inner classes inherited from class javax.swing.JComponent

JComponent.AccessibleJComponent

Field Summary

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 The action to take when the defaultButton is pressed.
protected javax.swing.JRootPane.DefaultAction	defaultReleaseAction The action to take when the defaultButton is released.
protected Component	glassPane The glass pane that overlays the menu bar and content pane, so it can intercept mouse movements and such.
protected JLayeredPane	layeredPane The layered pane that manages the menu bar and content pane.
protected JMenuBar	menuBar The menu bar.

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

Constructor Summary

JRootPane()
Create 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.
Component	findComponentAt(int x, int y) Locates the visible child component that contains the specified position.
AccessibleContext	getAccessibleContext() Get the AccessibleContext associated with this JComponent
Container	getContentPane() Returns the content pane -- the container that holds the components parented by the root pane.
JButton	getDefaultButton() Returns the current default button for this JRootPane.
Component	getGlassPane() Returns the current glass pane for this JRootPane.
JMenuBar	getJMenuBar() Returns the menu bar from the layered pane.
JLayeredPane	getLayeredPane() Get the layered pane used by the root pane.
JMenuBar	getMenuBar() Deprecated. As of Swing version 1.0.3 replaced by getJMenubar().
boolean	isFocusCycleRoot() Make JRootPane be the root of a focus cycle.
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 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) Set the layered pane for the root pane.
void	setMenuBar(JMenuBar menu) Deprecated. As of Swing version 1.0.3 replaced by setJMenuBar(JMenuBar menu).

Methods inherited from class javax.swing.JComponent

addAncestorListener, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInsets, getInsets, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getUIClassID, getVisibleRect, getWidth, getX, getY, grabFocus, hasFocus, isDoubleBuffered, isFocusTraversable, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, processComponentKeyEvent, processFocusEvent, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setDebugGraphicsOptions, setDoubleBuffered, setEnabled, setFont, setForeground, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setUI, setVisible, unregisterKeyboardAction, update, updateUI

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, countComponents, deliverEvent, doLayout, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getLayout, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paintComponents, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, setCursor, setLayout, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hide, imageUpdate, inside, isDisplayable, isEnabled, isLightweight, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processInputMethodEvent, processMouseEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setDropTarget, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

menuBar

protected JMenuBar menuBar

The menu bar.

contentPane

protected Container contentPane

The content pane.

layeredPane

protected JLayeredPane layeredPane

The layered pane that manages the menu bar and content pane.

glassPane

protected Component glassPane

The glass pane that overlays the menu bar and content pane, so it can intercept mouse movements and such.

defaultButton

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.

defaultPressAction

protected javax.swing.JRootPane.DefaultAction defaultPressAction

The action to take when the defaultButton is pressed.

See Also:

defaultButton

defaultReleaseAction

protected javax.swing.JRootPane.DefaultAction defaultReleaseAction

The action to take when the defaultButton is released.

See Also:

defaultButton

Constructor Detail

JRootPane

public JRootPane()

Create a JRootPane, setting up its glassPane, LayeredPane, and contentPane.

Method Detail

createLayeredPane

protected JLayeredPane createLayeredPane()

Called by the constructor methods to create the default layeredPane. Bt default it creates a new JLayeredPane.

createContentPane

protected Container createContentPane()

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.

createGlassPane

protected Component createGlassPane()

Called by the constructor methods to create the default glassPane. By default this method creates a new JComponent with visibility set to false.

createRootLayout

protected LayoutManager createRootLayout()

Called by the constructor methods to create the default layoutManager.

setJMenuBar

public void setJMenuBar(JMenuBar menu)

Adds or changes the menu bar used in the layered pane.

Parameters:

menu - the JMenuBar to add

setMenuBar

public void setMenuBar(JMenuBar menu)

Deprecated. As of Swing version 1.0.3 replaced by setJMenuBar(JMenuBar menu).

Specifies the menu bar value.

getJMenuBar

public JMenuBar getJMenuBar()

Returns the menu bar from the layered pane.

Returns:

the JMenuBar used in the pane

getMenuBar

public JMenuBar getMenuBar()

Deprecated. As of Swing version 1.0.3 replaced by getJMenubar().

Returns the menu bar value.

setContentPane

public void setContentPane(Container content)

Sets the content pane -- the container that holds the components parented by the root pane.

Parameters:

content - the Container to use for component-contents

Throws:

IllegalComponentStateException - (a runtime exception) if the content pane parameter is null

getContentPane

public Container getContentPane()

Returns the content pane -- the container that holds the components parented by the root pane.

Returns:

the Container that holds the component-contents

setLayeredPane

public void setLayeredPane(JLayeredPane layered)

Set the layered pane for the root pane. The layered pane typically holds a content pane and an optional JMenuBar.

Parameters:

layered - the JLayeredPane to use.

Throws:

IllegalComponentStateException - (a runtime exception) if the layered pane parameter is null

getLayeredPane

public JLayeredPane getLayeredPane()

Get the layered pane used by the root pane. The layered pane typically holds a content pane and an optional JMenuBar.

Returns:

the JLayeredPane currently in use

setGlassPane

public void setGlassPane(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. For example, only one JInternalFrame is ever active when using a DefaultDesktop, and any inactive JInternalFrames' glass panes are made visible so that clicking anywhere within an inactive JInternalFrame can activate it.

Parameters:

glass - the Component to use as the glass pane for this JRootPane.

getGlassPane

public Component getGlassPane()

Returns the current glass pane for this JRootPane.

Returns:

the current glass pane.

See Also:

setGlassPane(java.awt.Component)

isFocusCycleRoot

public boolean isFocusCycleRoot()

Make JRootPane be the root of a focus cycle. That means that, by default, tabbing within the root pane will move between components of the pane, but not out of the pane.

Overrides:

isFocusCycleRoot in class JComponent

Returns:

true

See Also:

JComponent.isFocusCycleRoot()

isValidateRoot

public boolean isValidateRoot()

If a descendant of this JRootPane calls revalidate, validate from here on down.

Deferred requests to relayout a component and it's descendants, i.e. calls to revalidate(), are pushed upwards to either a JRootPane or a JScrollPane because both classes override isValidateRoot() to return true.

Overrides:

isValidateRoot in class JComponent

Returns:

true

See Also:

JComponent.isValidateRoot()

addNotify

public void addNotify()

Register ourselves with the SystemEventQueueUtils as a new root pane.

Overrides:

addNotify in class JComponent

Tags copied from class: JComponent

See Also:

JComponent.registerKeyboardAction(java.awt.event.ActionListener, java.lang.String, javax.swing.KeyStroke, int)

removeNotify

public void removeNotify()

Unregister ourselves from SystemEventQueueUtils.

Overrides:

removeNotify in class JComponent

Tags copied from class: JComponent

See Also:

JComponent.registerKeyboardAction(java.awt.event.ActionListener, java.lang.String, javax.swing.KeyStroke, int)

setDefaultButton

public void setDefaultButton(JButton defaultButton)

Sets 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 RootPane regardless of whether or not the button has keyboard focus (unless there is another component within the RootPane which consumes the activation event, such as a JTextPane). For default activation to work, the button must be an enabled descendent of the RootPane when activation occurs. To remove a default button from this RootPane, set this property to null.

Parameters:

default - the JButton which is to be the default button

See Also:

JButton.isDefaultButton()

getDefaultButton

public JButton getDefaultButton()

Returns the current default button for this JRootPane.

Returns:

the JButton which is currently the default button

addImpl

protected void addImpl(Component comp,
                       Object constraints,
                       int index)

Overridden to enforce the position of the glass component as the zero child.

Overrides:

addImpl in class Container

Tags copied from class: Container

Parameters:

comp - the component to be added.

constraints - an object expressing layout contraints for this component.

index - the position in the container's list at which to insert the component, where -1 means insert at the end.

See Also:

Container.add(java.awt.Component), Container.add(java.awt.Component, int), Container.add(java.awt.Component, java.lang.Object), LayoutManager

findComponentAt

public Component findComponentAt(int x,
                                 int y)

Locates the visible child component that contains the specified position. The top-most child component is returned in the case where there is overlap in the components. If the containing child component is a Container, this method will continue searching for the deepest nested child component. Components which are not visible are ignored during the search.

This method is similar to Container.findComponentAt, except that the JRootPane.glassPane is ignored during the search. This is needed to to support drag&drop. Since the glassPane is the same size as the JRootPane instance, if there's a need to test whether the mouse is over the glassPane, just test that it's over the JRootPane instead.

Overrides:

findComponentAt in class Container

Parameters:

x - the x coordinate

y - the yReturns:

null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of this instance, then this JRootPane itself is returned.

See Also:

Container.findComponentAt, Container.getComponentAt

paramString

protected String paramString()

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.

Overrides:

paramString in class JComponent

Returns:

a string representation of this JRootPane.

getAccessibleContext

public AccessibleContext getAccessibleContext()

Get the AccessibleContext associated with this JComponent

Specified by:

getAccessibleContext in interface Accessible

Overrides:

getAccessibleContext in class JComponent

Returns:

the AccessibleContext of this JComponent