https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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package javax.swing;

import java.awt.Component;
import java.util.ArrayList;
import java.util.Hashtable;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import sun.awt.SunToolkit;

import javax.accessibility.*;


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: 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 JavaBeans™
has been added to the java.beans package. Please see XMLEncoder. 
Author:David Kloba
/**
 * <code>JLayeredPane</code> adds depth to a JFC/Swing container,
 * allowing components to overlap each other when needed.
 * An <code>Integer</code> object specifies each component's depth in the
 * container, where higher-numbered components sit &quot;on top&quot; of other
 * components.
 * For task-oriented documentation and examples of using layered panes see
 * <a href="https://docs.oracle.com/javase/tutorial/uiswing/components/layeredpane.html">How to Use a Layered Pane</a>,
 * a section in <em>The Java Tutorial</em>.
 *
 * <TABLE STYLE="FLOAT:RIGHT" BORDER="0" SUMMARY="layout">
 * <TR>
 *   <TD ALIGN="CENTER">
 *     <P STYLE="TEXT-ALIGN:CENTER"><IMG SRC="doc-files/JLayeredPane-1.gif"
 *     alt="The following text describes this image."
 *     WIDTH="269" HEIGHT="264" STYLE="FLOAT:BOTTOM; BORDER=0">
 *   </TD>
 * </TR>
 * </TABLE>
 * For convenience, <code>JLayeredPane</code> 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:
 * <DL>
 *    <DT><FONT SIZE="2">DEFAULT_LAYER</FONT></DT>
 *         <DD>The standard layer, where most components go. This the bottommost
 *         layer.
 *    <DT><FONT SIZE="2">PALETTE_LAYER</FONT></DT>
 *         <DD>The palette layer sits over the default layer. Useful for floating
 *         toolbars and palettes, so they can be positioned above other components.
 *    <DT><FONT SIZE="2">MODAL_LAYER</FONT></DT>
 *         <DD>The layer used for modal dialogs. They will appear on top of any
 *         toolbars, palettes, or standard components in the container.
 *    <DT><FONT SIZE="2">POPUP_LAYER</FONT></DT>
 *         <DD>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.
 *    <DT><FONT SIZE="2">DRAG_LAYER</FONT></DT>
 *         <DD>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.
 * </DL>
 * The <code>JLayeredPane</code> methods <code>moveToFront(Component)</code>,
 * <code>moveToBack(Component)</code> and <code>setPosition</code> can be used
 * to reposition a component within its layer. The <code>setLayer</code> method
 * can also be used to change the component's current layer.
 *
 * <h2>Details</h2>
 * <code>JLayeredPane</code> manages its list of children like
 * <code>Container</code>, but allows for the definition of a several
 * layers within itself. Children in the same layer are managed exactly
 * like the normal <code>Container</code> object,
 * with the added feature that when children components overlap, children
 * in higher layers display above the children in lower layers.
 * <p>
 * Each layer is a distinct integer number. The layer attribute can be set
 * on a <code>Component</code> by passing an <code>Integer</code>
 * object during the add call.<br> For example:
 * <PRE>
 *     layeredPane.add(child, JLayeredPane.DEFAULT_LAYER);
 * or
 *     layeredPane.add(child, new Integer(10));
 * </PRE>
 * The layer attribute can also be set on a Component by calling<PRE>
 *     layeredPaneParent.setLayer(child, 10)</PRE>
 * on the <code>JLayeredPane</code> that is the parent of component. The layer
 * should be set <i>before</i> adding the child to the parent.
 * <p>
 * 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:<PRE>
 *       5a, 5b, 5c, 2a, 2b, 2c, 1a </PRE>
 * where the leftmost components are closest to the top of the display.
 * <p>
 * A component can be moved to the top or bottom position within its
 * layer by calling <code>moveToFront</code> or <code>moveToBack</code>.
 * <p>
 * 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 <i>lower</i> in the display.
 * <blockquote>
 * <b>Note:</b> This sequence (defined by java.awt.Container) is the reverse
 * of the layer numbering sequence. Usually though, you will use <code>moveToFront</code>,
 * <code>moveToBack</code>, and <code>setLayer</code>.
 * </blockquote>
 * Here are some examples using the method add(Component, layer, position):
 * Calling add(5x, 5, -1) results in:<PRE>
 *       5a, 5b, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
 *
 * Calling add(5z, 5, 2) results in:<PRE>
 *       5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1a </PRE>
 *
 * Calling add(3a, 3, 7) results in:<PRE>
 *       5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1a </PRE>
 *
 * Using normal paint/event mechanics results in 1a appearing at the bottom
 * and 5a being above all other components.
 * <p>
 * <b>Note:</b> that these layers are simply a logical construct and LayoutManagers
 * will affect all child components of this container without regard for
 * layer settings.
 * <p>
 * <strong>Warning:</strong> Swing is not thread safe. For more
 * information see <a
 * href="package-summary.html#threading">Swing's Threading
 * Policy</a>.
 * <p>
 * <strong>Warning:</strong>
 * 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&trade;
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @author David Kloba
 */
@SuppressWarnings("serial")
public class JLayeredPane extends JComponent implements Accessible {
    /// Watch the values in getObjectForLayer()
    
Convenience object defining the Default layer. Equivalent to new Integer(0).
/** Convenience object defining the Default layer. Equivalent to new Integer(0).*/
    public final static Integer DEFAULT_LAYER = new Integer(0);
    
Convenience object defining the Palette layer. Equivalent to new Integer(100).
/** Convenience object defining the Palette layer. Equivalent to new Integer(100).*/
    public final static Integer PALETTE_LAYER = new Integer(100);
    
Convenience object defining the Modal layer. Equivalent to new Integer(200).
/** Convenience object defining the Modal layer. Equivalent to new Integer(200).*/
    public final static Integer MODAL_LAYER = new Integer(200);
    
Convenience object defining the Popup layer. Equivalent to new Integer(300).
/** Convenience object defining the Popup layer. Equivalent to new Integer(300).*/
    public final static Integer POPUP_LAYER = new Integer(300);
    
Convenience object defining the Drag layer. Equivalent to new Integer(400).
/** Convenience object defining the Drag layer. Equivalent to new Integer(400).*/
    public final static Integer DRAG_LAYER = new Integer(400);
    
Convenience object defining the Frame Content layer.
This layer is normally only use to position the contentPane and menuBar
components of JFrame.
Equivalent to new Integer(-30000).

See Also:
  • JFrame
/** Convenience object defining the Frame Content layer.
      * This layer is normally only use to position the contentPane and menuBar
      * components of JFrame.
      * Equivalent to new Integer(-30000).
      * @see JFrame
      */
    public final static Integer FRAME_CONTENT_LAYER = new Integer(-30000);

    
Bound property 
/** Bound property */
    public final static String LAYER_PROPERTY = "layeredContainerLayer";
    // Hashtable to store layer values for non-JComponent components
    private Hashtable<Component,Integer> componentToLayer;
    private boolean optimizedDrawingPossible = true;


//////////////////////////////////////////////////////////////////////////////
//// Container Override methods
//////////////////////////////////////////////////////////////////////////////
    
Create a new JLayeredPane 
/** Create a new JLayeredPane */
    public JLayeredPane() {
        setLayout(null);
    }

    private void validateOptimizedDrawing() {
        boolean layeredComponentFound = false;
        synchronized(getTreeLock()) {
            Integer layer;

            for (Component c : getComponents()) {
                layer = null;

                if(SunToolkit.isInstanceOf(c, "javax.swing.JInternalFrame") ||
                       (c instanceof JComponent &&
                        (layer = (Integer)((JComponent)c).
                                     getClientProperty(LAYER_PROPERTY)) != null))
                {
                    if(layer != null && layer.equals(FRAME_CONTENT_LAYER))
                        continue;
                    layeredComponentFound = true;
                    break;
                }
            }
        }

        if(layeredComponentFound)
            optimizedDrawingPossible = false;
        else
            optimizedDrawingPossible = true;
    }

    protected void addImpl(Component comp, Object constraints, int index) {
        int layer;
        int pos;

        if(constraints instanceof Integer) {
            layer = ((Integer)constraints).intValue();
            setLayer(comp, layer);
        } else
            layer = getLayer(comp);

        pos = insertIndexForLayer(layer, index);
        super.addImpl(comp, constraints, pos);
        comp.validate();
        comp.repaint();
        validateOptimizedDrawing();
    }

    
Remove the indexed component from this pane.
This is the absolute index, ignoring layers.

Params:
  • index –  an int specifying the component to remove
See Also:
/**
     * Remove the indexed component from this pane.
     * This is the absolute index, ignoring layers.
     *
     * @param index  an int specifying the component to remove
     * @see #getIndexOf
     */
    public void remove(int index) {
        Component c = getComponent(index);
        super.remove(index);
        if (c != null && !(c instanceof JComponent)) {
            getComponentToLayer().remove(c);
        }
        validateOptimizedDrawing();
    }

    
Removes all the components from this container.

Since:1.5
/**
     * Removes all the components from this container.
     *
     * @since 1.5
     */
    public void removeAll() {
        Component[] children = getComponents();
        Hashtable<Component, Integer> cToL = getComponentToLayer();
        for (int counter = children.length - 1; counter >= 0; counter--) {
            Component c = children[counter];
            if (c != null && !(c instanceof JComponent)) {
                cToL.remove(c);
            }
        }
        super.removeAll();
    }

    
Returns false if components in the pane can overlap, which makes
optimized drawing impossible. Otherwise, returns true.

See Also:
Returns:false if components can overlap, else true
/**
     * Returns false if components in the pane can overlap, which makes
     * optimized drawing impossible. Otherwise, returns true.
     *
     * @return false if components can overlap, else true
     * @see JComponent#isOptimizedDrawingEnabled
     */
    public boolean isOptimizedDrawingEnabled() {
        return optimizedDrawingPossible;
    }


//////////////////////////////////////////////////////////////////////////////
//// New methods for managing layers
//////////////////////////////////////////////////////////////////////////////
    
Sets the layer property on a JComponent. This method does not cause
any side effects like setLayer() (painting, add/remove, etc).
Normally you should use the instance method setLayer(), in order to
get the desired side-effects (like repainting).

Params:
  • c –      the JComponent to move
  • layer –  an int specifying the layer to move it to
See Also:
/** Sets the layer property on a JComponent. This method does not cause
      * any side effects like setLayer() (painting, add/remove, etc).
      * Normally you should use the instance method setLayer(), in order to
      * get the desired side-effects (like repainting).
      *
      * @param c      the JComponent to move
      * @param layer  an int specifying the layer to move it to
      * @see #setLayer
      */
    public static void putLayer(JComponent c, int layer) {
        /// MAKE SURE THIS AND setLayer(Component c, int layer, int position)  are SYNCED
        Integer layerObj;

        layerObj = new Integer(layer);
        c.putClientProperty(LAYER_PROPERTY, layerObj);
    }

    
Gets the layer property for a JComponent, it
does not cause any side effects like setLayer(). (painting, add/remove, etc)
Normally you should use the instance method getLayer().

Params:
  • c –  the JComponent to check
Returns:  an int specifying the component's layer
/** Gets the layer property for a JComponent, it
      * does not cause any side effects like setLayer(). (painting, add/remove, etc)
      * Normally you should use the instance method getLayer().
      *
      * @param c  the JComponent to check
      * @return   an int specifying the component's layer
      */
    public static int getLayer(JComponent c) {
        Integer i;
        if((i = (Integer)c.getClientProperty(LAYER_PROPERTY)) != null)
            return i.intValue();
        return DEFAULT_LAYER.intValue();
    }

    
Convenience method that returns the first JLayeredPane which
contains the specified component. Note that all JFrames have a
JLayeredPane at their root, so any component in a JFrame will
have a JLayeredPane parent.

Params:
  • c – the Component to check
See Also:
Returns:the JLayeredPane that contains the component, or
        null if no JLayeredPane is found in the component
        hierarchy
/** Convenience method that returns the first JLayeredPane which
      * contains the specified component. Note that all JFrames have a
      * JLayeredPane at their root, so any component in a JFrame will
      * have a JLayeredPane parent.
      *
      * @param c the Component to check
      * @return the JLayeredPane that contains the component, or
      *         null if no JLayeredPane is found in the component
      *         hierarchy
      * @see JFrame
      * @see JRootPane
      */
    public static JLayeredPane getLayeredPaneAbove(Component c) {
        if(c == null) return null;

        Component parent = c.getParent();
        while(parent != null && !(parent instanceof JLayeredPane))
            parent = parent.getParent();
        return (JLayeredPane)parent;
    }

    
Sets the layer attribute on the specified component,
making it the bottommost component in that layer.
Should be called before adding to parent.

Params:
  • c –     the Component to set the layer for
  • layer – an int specifying the layer to set, where
             lower numbers are closer to the bottom
/** Sets the layer attribute on the specified component,
      * making it the bottommost component in that layer.
      * Should be called before adding to parent.
      *
      * @param c     the Component to set the layer for
      * @param layer an int specifying the layer to set, where
      *              lower numbers are closer to the bottom
      */
    public void setLayer(Component c, int layer)  {
        setLayer(c, layer, -1);
    }

    
Sets the layer attribute for the specified component and
also sets its position within that layer.

Params:
  • c –         the Component to set the layer for
  • layer –     an int specifying the layer to set, where
                 lower numbers are closer to the bottom
  • position –  an int specifying the position within the
                 layer, where 0 is the topmost position and -1
                 is the bottommost position
/** Sets the layer attribute for the specified component and
      * also sets its position within that layer.
      *
      * @param c         the Component to set the layer for
      * @param layer     an int specifying the layer to set, where
      *                  lower numbers are closer to the bottom
      * @param position  an int specifying the position within the
      *                  layer, where 0 is the topmost position and -1
      *                  is the bottommost position
      */
    public void setLayer(Component c, int layer, int position)  {
        Integer layerObj;
        layerObj = getObjectForLayer(layer);

        if(layer == getLayer(c) && position == getPosition(c)) {
                repaint(c.getBounds());
            return;
        }

        /// MAKE SURE THIS AND putLayer(JComponent c, int layer) are SYNCED
        if(c instanceof JComponent)
            ((JComponent)c).putClientProperty(LAYER_PROPERTY, layerObj);
        else
            getComponentToLayer().put(c, layerObj);

        if(c.getParent() == null || c.getParent() != this) {
            repaint(c.getBounds());
            return;
        }

        int index = insertIndexForLayer(c, layer, position);

        setComponentZOrder(c, index);
        repaint(c.getBounds());
    }

    
Returns the layer attribute for the specified Component.

Params:
  • c –  the Component to check
Returns:an int specifying the component's current layer
/**
     * Returns the layer attribute for the specified Component.
     *
     * @param c  the Component to check
     * @return an int specifying the component's current layer
     */
    public int getLayer(Component c) {
        Integer i;
        if(c instanceof JComponent)
            i = (Integer)((JComponent)c).getClientProperty(LAYER_PROPERTY);
        else
            i = getComponentToLayer().get(c);

        if(i == null)
            return DEFAULT_LAYER.intValue();
        return i.intValue();
    }

    
Returns the index of the specified Component.
This is the absolute index, ignoring layers.
Index numbers, like position numbers, have the topmost component
at index zero. Larger numbers are closer to the bottom.

Params:
  • c –  the Component to check
Returns:an int specifying the component's index
/**
     * Returns the index of the specified Component.
     * This is the absolute index, ignoring layers.
     * Index numbers, like position numbers, have the topmost component
     * at index zero. Larger numbers are closer to the bottom.
     *
     * @param c  the Component to check
     * @return an int specifying the component's index
     */
    public int getIndexOf(Component c) {
        int i, count;

        count = getComponentCount();
        for(i = 0; i < count; i++) {
            if(c == getComponent(i))
                return i;
        }
        return -1;
    }
    
Moves the component to the top of the components in its current layer
(position 0).

Params:
  • c – the Component to move
See Also:
/**
     * Moves the component to the top of the components in its current layer
     * (position 0).
     *
     * @param c the Component to move
     * @see #setPosition(Component, int)
     */
    public void moveToFront(Component c) {
        setPosition(c, 0);
    }

    
Moves the component to the bottom of the components in its current layer
(position -1).

Params:
  • c – the Component to move
See Also:
/**
     * Moves the component to the bottom of the components in its current layer
     * (position -1).
     *
     * @param c the Component to move
     * @see #setPosition(Component, int)
     */
    public void moveToBack(Component c) {
        setPosition(c, -1);
    }

    
Moves the component to position within its current layer,
where 0 is the topmost position within the layer and -1 is the bottommost
position.


Note: Position numbering is defined by java.awt.Container, and
is the opposite of layer numbering. Lower position numbers are closer
to the top (0 is topmost), and higher position numbers are closer to
the bottom.

Params:
  • c –         the Component to move
  • position –  an int in the range -1..N-1, where N is the number of
                 components in the component's current layer
/**
     * Moves the component to <code>position</code> within its current layer,
     * where 0 is the topmost position within the layer and -1 is the bottommost
     * position.
     * <p>
     * <b>Note:</b> Position numbering is defined by java.awt.Container, and
     * is the opposite of layer numbering. Lower position numbers are closer
     * to the top (0 is topmost), and higher position numbers are closer to
     * the bottom.
     *
     * @param c         the Component to move
     * @param position  an int in the range -1..N-1, where N is the number of
     *                  components in the component's current layer
     */
    public void setPosition(Component c, int position) {
        setLayer(c, getLayer(c), position);
    }

    
Get the relative position of the component within its layer.

Params:
  • c –  the Component to check
See Also:
Returns:an int giving the component's position, where 0 is the
        topmost position and the highest index value = the count
        count of components at that layer, minus 1
/**
     * Get the relative position of the component within its layer.
     *
     * @param c  the Component to check
     * @return an int giving the component's position, where 0 is the
     *         topmost position and the highest index value = the count
     *         count of components at that layer, minus 1
     *
     * @see #getComponentCountInLayer
     */
    public int getPosition(Component c) {
        int i, startLayer, curLayer, startLocation, pos = 0;

        getComponentCount();
        startLocation = getIndexOf(c);

        if(startLocation == -1)
            return -1;

        startLayer = getLayer(c);
        for(i = startLocation - 1; i >= 0; i--) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == startLayer)
                pos++;
            else
                return pos;
        }
        return pos;
    }

    
Returns the highest layer value from all current children.
Returns 0 if there are no children.

Returns:an int indicating the layer of the topmost component in the
        pane, or zero if there are no children
/** Returns the highest layer value from all current children.
      * Returns 0 if there are no children.
      *
      * @return an int indicating the layer of the topmost component in the
      *         pane, or zero if there are no children
      */
    public int highestLayer() {
        if(getComponentCount() > 0)
            return getLayer(getComponent(0));
        return 0;
    }

    
Returns the lowest layer value from all current children.
Returns 0 if there are no children.

Returns:an int indicating the layer of the bottommost component in the
        pane, or zero if there are no children
/** Returns the lowest layer value from all current children.
      * Returns 0 if there are no children.
      *
      * @return an int indicating the layer of the bottommost component in the
      *         pane, or zero if there are no children
      */
    public int lowestLayer() {
        int count = getComponentCount();
        if(count > 0)
            return getLayer(getComponent(count-1));
        return 0;
    }

    
Returns the number of children currently in the specified layer.

Params:
  • layer –  an int specifying the layer to check
Returns:an int specifying the number of components in that layer
/**
     * Returns the number of children currently in the specified layer.
     *
     * @param layer  an int specifying the layer to check
     * @return an int specifying the number of components in that layer
     */
    public int getComponentCountInLayer(int layer) {
        int i, count, curLayer;
        int layerCount = 0;

        count = getComponentCount();
        for(i = 0; i < count; i++) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == layer) {
                layerCount++;
            /// Short circut the counting when we have them all
            } else if(layerCount > 0 || curLayer < layer) {
                break;
            }
        }

        return layerCount;
    }

    
Returns an array of the components in the specified layer.

Params:
  • layer –  an int specifying the layer to check
Returns:an array of Components contained in that layer
/**
     * Returns an array of the components in the specified layer.
     *
     * @param layer  an int specifying the layer to check
     * @return an array of Components contained in that layer
     */
    public Component[] getComponentsInLayer(int layer) {
        int i, count, curLayer;
        int layerCount = 0;
        Component[] results;

        results = new Component[getComponentCountInLayer(layer)];
        count = getComponentCount();
        for(i = 0; i < count; i++) {
            curLayer = getLayer(getComponent(i));
            if(curLayer == layer) {
                results[layerCount++] = getComponent(i);
            /// Short circut the counting when we have them all
            } else if(layerCount > 0 || curLayer < layer) {
                break;
            }
        }

        return results;
    }

    
Paints this JLayeredPane within the specified graphics context.

Params:
  • g –  the Graphics context within which to paint
/**
     * Paints this JLayeredPane within the specified graphics context.
     *
     * @param g  the Graphics context within which to paint
     */
    public void paint(Graphics g) {
        if(isOpaque()) {
            Rectangle r = g.getClipBounds();
            Color c = getBackground();
            if(c == null)
                c = Color.lightGray;
            g.setColor(c);
            if (r != null) {
                g.fillRect(r.x, r.y, r.width, r.height);
            }
            else {
                g.fillRect(0, 0, getWidth(), getHeight());
            }
        }
        super.paint(g);
    }

//////////////////////////////////////////////////////////////////////////////
//// Implementation Details
//////////////////////////////////////////////////////////////////////////////

    
Returns the hashtable that maps components to layers.

Returns:the Hashtable used to map components to their layers
/**
     * Returns the hashtable that maps components to layers.
     *
     * @return the Hashtable used to map components to their layers
     */
    protected Hashtable<Component,Integer> getComponentToLayer() {
        if(componentToLayer == null)
            componentToLayer = new Hashtable<Component,Integer>(4);
        return componentToLayer;
    }

    
Returns the Integer object associated with a specified layer.

Params:
  • layer – an int specifying the layer
Returns:an Integer object for that layer
/**
     * Returns the Integer object associated with a specified layer.
     *
     * @param layer an int specifying the layer
     * @return an Integer object for that layer
     */
    protected Integer getObjectForLayer(int layer) {
        Integer layerObj;
        switch(layer) {
        case 0:
            layerObj = DEFAULT_LAYER;
            break;
        case 100:
            layerObj = PALETTE_LAYER;
            break;
        case 200:
            layerObj = MODAL_LAYER;
            break;
        case 300:
            layerObj = POPUP_LAYER;
            break;
        case 400:
            layerObj = DRAG_LAYER;
            break;
        default:
            layerObj = new Integer(layer);
        }
        return layerObj;
    }

    
Primitive method that determines the proper location to
insert a new child based on layer and position requests.

Params:
  • layer –     an int specifying the layer
  • position –  an int specifying the position within the layer
See Also:
Returns:an int giving the (absolute) insertion-index
/**
     * Primitive method that determines the proper location to
     * insert a new child based on layer and position requests.
     *
     * @param layer     an int specifying the layer
     * @param position  an int specifying the position within the layer
     * @return an int giving the (absolute) insertion-index
     *
     * @see #getIndexOf
     */
    protected int insertIndexForLayer(int layer, int position) {
        return insertIndexForLayer(null, layer, position);
    }

    
This method is an extended version of insertIndexForLayer()
to support setLayer which uses Container.setZOrder which does
not remove the component from the containment hierarchy though
we need to ignore it when calculating the insertion index.

Params:
  • comp –      component to ignore when determining index
  • layer –     an int specifying the layer
  • position –  an int specifying the position within the layer
See Also:
Returns:an int giving the (absolute) insertion-index
/**
     * This method is an extended version of insertIndexForLayer()
     * to support setLayer which uses Container.setZOrder which does
     * not remove the component from the containment hierarchy though
     * we need to ignore it when calculating the insertion index.
     *
     * @param comp      component to ignore when determining index
     * @param layer     an int specifying the layer
     * @param position  an int specifying the position within the layer
     * @return an int giving the (absolute) insertion-index
     *
     * @see #getIndexOf
     */
    private int insertIndexForLayer(Component comp, int layer, int position) {
        int i, count, curLayer;
        int layerStart = -1;
        int layerEnd = -1;
        int componentCount = getComponentCount();

        ArrayList<Component> compList =
            new ArrayList<Component>(componentCount);
        for (int index = 0; index < componentCount; index++) {
            if (getComponent(index) != comp) {
                compList.add(getComponent(index));
            }
        }

        count = compList.size();
        for (i = 0; i < count; i++) {
            curLayer = getLayer(compList.get(i));
            if (layerStart == -1 && curLayer == layer) {
                layerStart = i;
            }
            if (curLayer < layer) {
                if (i == 0) {
                    // layer is greater than any current layer
                    // [ ASSERT(layer > highestLayer()) ]
                    layerStart = 0;
                    layerEnd = 0;
                } else {
                    layerEnd = i;
                }
                break;
            }
        }

        // layer requested is lower than any current layer
        // [ ASSERT(layer < lowestLayer()) ]
        // put it on the bottom of the stack
        if (layerStart == -1 && layerEnd == -1)
            return count;

        // In the case of a single layer entry handle the degenerative cases
        if (layerStart != -1 && layerEnd == -1)
            layerEnd = count;

        if (layerEnd != -1 && layerStart == -1)
            layerStart = layerEnd;

        // If we are adding to the bottom, return the last element
        if (position == -1)
            return layerEnd;

        // Otherwise make sure the requested position falls in the
        // proper range
        if (position > -1 && layerStart + position <= layerEnd)
            return layerStart + position;

        // Otherwise return the end of the layer
        return layerEnd;
    }

    
Returns a string representation of this JLayeredPane. 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.

Returns: a string representation of this JLayeredPane.
/**
     * Returns a string representation of this JLayeredPane. 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 <code>null</code>.
     *
     * @return  a string representation of this JLayeredPane.
     */
    protected String paramString() {
        String optimizedDrawingPossibleString = (optimizedDrawingPossible ?
                                                 "true" : "false");

        return super.paramString() +
        ",optimizedDrawingPossible=" + optimizedDrawingPossibleString;
    }

/////////////////
// Accessibility support
////////////////

    
Gets the AccessibleContext associated with this JLayeredPane.
For layered panes, the AccessibleContext takes the form of an
AccessibleJLayeredPane.
A new AccessibleJLayeredPane instance is created if necessary.

Returns:an AccessibleJLayeredPane that serves as the
        AccessibleContext of this JLayeredPane
/**
     * Gets the AccessibleContext associated with this JLayeredPane.
     * For layered panes, the AccessibleContext takes the form of an
     * AccessibleJLayeredPane.
     * A new AccessibleJLayeredPane instance is created if necessary.
     *
     * @return an AccessibleJLayeredPane that serves as the
     *         AccessibleContext of this JLayeredPane
     */
    public AccessibleContext getAccessibleContext() {
        if (accessibleContext == null) {
            accessibleContext = new AccessibleJLayeredPane();
        }
        return accessibleContext;
    }

    
This class implements accessibility support for the
JLayeredPane class.  It provides an implementation of the
Java Accessibility API appropriate to layered pane user-interface
elements.


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™
has been added to the java.beans package. Please see XMLEncoder. 
/**
     * This class implements accessibility support for the
     * <code>JLayeredPane</code> class.  It provides an implementation of the
     * Java Accessibility API appropriate to layered pane user-interface
     * elements.
     * <p>
     * <strong>Warning:</strong>
     * 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&trade;
     * has been added to the <code>java.beans</code> package.
     * Please see {@link java.beans.XMLEncoder}.
     */
    @SuppressWarnings("serial")
    protected class AccessibleJLayeredPane extends AccessibleJComponent {

        
Get the role of this object.

See Also:
Returns:an instance of AccessibleRole describing the role of the
object
/**
         * Get the role of this object.
         *
         * @return an instance of AccessibleRole describing the role of the
         * object
         * @see AccessibleRole
         */
        public AccessibleRole getAccessibleRole() {
            return AccessibleRole.LAYERED_PANE;
        }
    }
}