javax.swing
Class JLayeredPane

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

All Implemented Interfaces:

ImageObserver , MenuContainer , Serializable , Accessible

Direct Known Subclasses:

JDesktopPane

public class JLayeredPane
extends JComponent   
implements Accessible   

JLayeredPane adds depth to a JFC/Swing container, allowing components to overlap each other when needed. An Integer object specifies each component's depth in the container, where higher-numbered components sit "on top" of other components. For task-oriented documentation and examples of using layered panes see How to Use a Layered Pane, a section in The Java Tutorial.

For convenience, JLayeredPane divides the depth-range into several different layers. Putting a component into one of those layers makes it easy to ensure that components overlap properly, without having to worry about specifying numbers for specific depths:

DEFAULT_LAYER

The standard layer, where most components go. This the bottommost layer.

PALETTE_LAYER

The palette layer sits over the default layer. Useful for floating toolbars and palettes, so they can be positioned above other components.

MODAL_LAYER

The layer used for modal dialogs. They will appear on top of any toolbars, palettes, or standard components in the container.

POPUP_LAYER

The popup layer displays above dialogs. That way, the popup windows associated with combo boxes, tooltips, and other help text will appear above the component, palette, or dialog that generated them.

DRAG_LAYER

When dragging a component, reassigning it to the drag layer ensures that it is positioned over every other component in the container. When finished dragging, it can be reassigned to its normal layer.

The JLayeredPane methods moveToFront(Component), moveToBack(Component) and setPosition can be used to reposition a component within its layer. The setLayer method can also be used to change the component's current layer.

Details

JLayeredPane manages its list of children like Container, but allows for the definition of a several layers within itself. Children in the same layer are managed exactly like the normal Container object, with the added feature that when children components overlap, children in higher layers display above the children in lower layers.

Each layer is a distinct integer number. The layer attribute can be set on a Component by passing an Integer object during the add call.
For example:

     layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
 or
     layeredPane.add(child, new Integer(10));
 

The layer attribute can also be set on a Component by calling

     layeredPaneParent.setLayer(child, 10)

on the JLayeredPane that is the parent of component. The layer should be set before adding the child to the parent.

Higher number layers display above lower number layers. So, using numbers for the layers and letters for individual components, a representative list order would look like this:

       5a, 5b, 5c, 2a, 2b, 2c, 1a 

where the leftmost components are closest to the top of the display.

A component can be moved to the top or bottom position within its layer by calling moveToFront or moveToBack.

The position of a component within a layer can also be specified directly. Valid positions range from 0 up to one less than the number of components in that layer. A value of -1 indicates the bottommost position. A value of 0 indicates the topmost position. Unlike layer numbers, higher position values are lower in the display.

Note: This sequence (defined by java.awt.Container) is the reverse of the layer numbering sequence. Usually though, you will use moveToFront, moveToBack, and setLayer.

Here are some examples using the method add(Component, layer, position): Calling add(5x, 5, -1) results in:

       5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a 

Calling add(5z, 5, 2) results in:

       5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a 

Calling add(3a, 3, 7) results in:

       5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a 

Using normal paint/event mechanics results in 1a appearing at the bottom and 5a being above all other components.

Note: that these layers are simply a logical construct and LayoutManagers will affect all child components of this container without regard for layer settings.

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:

Serialized Form

Nested Class Summary

protected class

JLayeredPane.AccessibleJLayeredPane This class implements accessibility support for the JLayeredPane class.

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 Integer	DEFAULT_LAYER Convenience object defining the Default layer.
static Integer	DRAG_LAYER Convenience object defining the Drag layer.
static Integer	FRAME_CONTENT_LAYER Convenience object defining the Frame Content layer.
static String	LAYER_PROPERTY Bound property
static Integer	MODAL_LAYER Convenience object defining the Modal layer.
static Integer	PALETTE_LAYER Convenience object defining the Palette layer.
static Integer	POPUP_LAYER Convenience object defining the Popup layer.

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

JLayeredPane ()
Create a new JLayeredPane

Method Summary

protected void	addImpl (Component comp, Object constraints, int index) Adds the specified component to this container at the specified index.
AccessibleContext	getAccessibleContext () Gets the AccessibleContext associated with this JLayeredPane.
int	getComponentCountInLayer (int layer) Returns the number of children currently in the specified layer.
Component []	getComponentsInLayer (int layer) Returns an array of the components in the specified layer.
protected Hashtable <Component ,Integer >	getComponentToLayer () Returns the hashtable that maps components to layers.
int	getIndexOf (Component c) Returns the index of the specified Component.
int	getLayer (Component c) Returns the layer attribute for the specified Component.
static int	getLayer (JComponent c) Gets the layer property for a JComponent, it does not cause any side effects like setLayer().
static JLayeredPane	getLayeredPaneAbove (Component c) Convenience method that returns the first JLayeredPane which contains the specified component.
protected Integer	getObjectForLayer (int layer) Returns the Integer object associated with a specified layer.
int	getPosition (Component c) Get the relative position of the component within its layer.
int	highestLayer () Returns the highest layer value from all current children.
protected int	insertIndexForLayer (int layer, int position) Primitive method that determines the proper location to insert a new child based on layer and position requests.
boolean	isOptimizedDrawingEnabled () Returns false if components in the pane can overlap, which makes optimized drawing impossible.
int	lowestLayer () Returns the lowest layer value from all current children.
void	moveToBack (Component c) Moves the component to the bottom of the components in its current layer (position -1).
void	moveToFront (Component c) Moves the component to the top of the components in its current layer (position 0).
void	paint (Graphics g) Paints this JLayeredPane within the specified graphics context.
protected String	paramString () Returns a string representation of this JLayeredPane.
static void	putLayer (JComponent c, int layer) Sets the layer property on a JComponent.
void	remove (int index) Remove the indexed component from this pane.
void	removeAll () Removes all the components from this container.
void	setLayer (Component c, int layer) Sets the layer attribute on the specified component, making it the bottommost component in that layer.
void	setLayer (Component c, int layer, int position) Sets the layer attribute for the specified component and also sets its position within that layer.
void	setPosition (Component c, int position) Moves the component to position within its current layer, where 0 is the topmost position within the layer and -1 is the bottommost position.

Methods inherited from class javax.swing.JComponent

addAncestorListener , addNotify , addVetoableChangeListener , computeVisibleRect , contains , createToolTip , disable , enable , firePropertyChange , firePropertyChange , firePropertyChange , fireVetoableChange , getActionForKeyStroke , getActionMap , getAlignmentX , getAlignmentY , getAncestorListeners , getAutoscrolls , getBorder , getBounds , getClientProperty , getComponentGraphics , getComponentPopupMenu , getConditionForKeyStroke , getDebugGraphicsOptions , getDefaultLocale , getFontMetrics , getGraphics , getHeight , getInheritsPopupMenu , getInputMap , getInputMap , getInputVerifier , getInsets , getInsets , getListeners , getLocation , getMaximumSize , getMinimumSize , getNextFocusableComponent , getPopupLocation , getPreferredSize , getRegisteredKeyStrokes , getRootPane , getSize , getToolTipLocation , getToolTipText , getToolTipText , getTopLevelAncestor , getTransferHandler