# 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`

@JavaBean(defaultProperty="accessibleContext") 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.

Example:

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, Integer.valueOf(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`.

Since:
  1.2

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `protected class`
  `JLayeredPane.AccessibleJLayeredPane`
  This class implements accessibility support for the `JLayeredPane` class.

  ### Nested classes/interfaces declared in class JComponent

  `JComponent.AccessibleJComponent`

  ### Nested classes/interfaces declared in class Container

  `Container.AccessibleAWTContainer`

  ### Nested classes/interfaces declared in class Component

  `Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy`

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final Integer`
  `DEFAULT_LAYER`
  Convenience object defining the Default layer.
  `static final Integer`
  `DRAG_LAYER`
  Convenience object defining the Drag layer.
  `static final Integer`
  `FRAME_CONTENT_LAYER`
  Convenience object defining the Frame Content layer.
  `static final String`
  `LAYER_PROPERTY`
  Bound property
  `static final Integer`
  `MODAL_LAYER`
  Convenience object defining the Modal layer.
  `static final Integer`
  `PALETTE_LAYER`
  Convenience object defining the Palette layer.
  `static final Integer`
  `POPUP_LAYER`
  Convenience object defining the Popup layer.

  ### Fields declared in class JComponent

  `listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW`

  ### Fields declared in class Component

  `accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT`

  ### Fields declared in interface ImageObserver

  `ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `JLayeredPane()`
  Create a new JLayeredPane

- ## Method Summary

  Modifier and Type
  Method
  Description
  `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 declared in class JComponent

  `addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBaseline, getBaselineResizeBehavior, 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, getUI, getUIClassID, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, hide, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isPaintingForPrint, isPaintingOrigin, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyEvent, processMouseEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setBorder, setComponentPopupMenu, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update, updateUI`

  ### Methods declared in class Container

  `add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, getMousePosition, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setLayout, transferFocusDownCycle, validate, validateTree`

  ### Methods declared in class Component

  `action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setMixingCutoutShape, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle`

  ### Methods declared in class Object

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

- ## Field Details

  - ### DEFAULT_LAYER

    public static final Integer DEFAULT_LAYER
    Convenience object defining the Default layer. Equivalent to Integer.valueOf(0).

  - ### PALETTE_LAYER

    public static final Integer PALETTE_LAYER
    Convenience object defining the Palette layer. Equivalent to Integer.valueOf(100).

  - ### MODAL_LAYER

    public static final Integer MODAL_LAYER
    Convenience object defining the Modal layer. Equivalent to Integer.valueOf(200).

  - ### POPUP_LAYER

    public static final Integer POPUP_LAYER
    Convenience object defining the Popup layer. Equivalent to Integer.valueOf(300).

  - ### DRAG_LAYER

    public static final Integer DRAG_LAYER
    Convenience object defining the Drag layer. Equivalent to Integer.valueOf(400).

  - ### FRAME_CONTENT_LAYER

    public static final Integer FRAME_CONTENT_LAYER
    Convenience object defining the Frame Content layer. This layer is normally only use to position the contentPane and menuBar components of JFrame. Equivalent to Integer.valueOf(-30000).
    See Also:
      - `JFrame`

  - ### LAYER_PROPERTY

    public static final String LAYER_PROPERTY
    Bound property
    See Also:
      - Constant Field Values

- ## Constructor Details

  - ### JLayeredPane

    public JLayeredPane()
    Create a new JLayeredPane

- ## Method Details

  - ### remove

    public void remove(int index)
    Remove the indexed component from this pane. This is the absolute index, ignoring layers.
    Overrides:
      `remove` in class `Container`
    Parameters:
      `index` - an int specifying the component to remove
    See Also:
      - `getIndexOf(Component)`

  - ### removeAll

    public void removeAll()
    Removes all the components from this container.
    Overrides:
      `removeAll` in class `Container`
    Since:
      1.5
    See Also:
      - `Container.add(Component)`
      - `Container.remove(int)`
      - `Container.invalidate()`

  - ### isOptimizedDrawingEnabled

    @BeanProperty(bound=false) public boolean isOptimizedDrawingEnabled()
    Returns false if components in the pane can overlap, which makes optimized drawing impossible. Otherwise, returns true.
    Overrides:
      `isOptimizedDrawingEnabled` in class `JComponent`
    Returns:
      false if components can overlap, else true
    See Also:
      - `JComponent.isOptimizedDrawingEnabled()`

  - ### putLayer

    public static void putLayer(JComponent c, int layer)
    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).
    Parameters:
      `c` - the JComponent to move
      `layer` - an int specifying the layer to move it to
    See Also:
      - `setLayer(Component, int)`

  - ### getLayer

    public static int getLayer(JComponent c)
    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().
    Parameters:
      `c` - the JComponent to check
    Returns:
      an int specifying the component's layer

  - ### getLayeredPaneAbove

    public static JLayeredPane getLayeredPaneAbove(Component c)
    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.
    Parameters:
      `c` - the Component to check
    Returns:
      the JLayeredPane that contains the component, or null if no JLayeredPane is found in the component hierarchy
    See Also:
      - `JFrame`
      - `JRootPane`

  - ### setLayer

    public void setLayer(Component c, int layer)
    Sets the layer attribute on the specified component, making it the bottommost component in that layer. Should be called before adding to parent.
    Parameters:
      `c` - the Component to set the layer for
      `layer` - an int specifying the layer to set, where lower numbers are closer to the bottom

  - ### setLayer

    public void setLayer(Component c, int layer, int position)
    Sets the layer attribute for the specified component and also sets its position within that layer.
    Parameters:
      `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

  - ### getLayer

    public int getLayer(Component c)
    Returns the layer attribute for the specified Component.
    Parameters:
      `c` - the Component to check
    Returns:
      an int specifying the component's current layer

  - ### getIndexOf

    public int getIndexOf(Component c)
    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.
    Parameters:
      `c` - the Component to check
    Returns:
      an int specifying the component's index

  - ### moveToFront

    public void moveToFront(Component c)
    Moves the component to the top of the components in its current layer (position 0).
    Parameters:
      `c` - the Component to move
    See Also:
      - `setPosition(Component, int)`

  - ### moveToBack

    public void moveToBack(Component c)
    Moves the component to the bottom of the components in its current layer (position -1).
    Parameters:
      `c` - the Component to move
    See Also:
      - `setPosition(Component, int)`

  - ### setPosition

    public 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.

    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.

    Parameters:
      `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

  - ### getPosition

    public int getPosition(Component c)
    Get the relative position of the component within its layer.
    Parameters:
      `c` - the Component to check
    Returns:
      an int giving the component's position, where 0 is the topmost position and the highest index value = the count of components at that layer minus 1
    See Also:
      - `getComponentCountInLayer(int)`

  - ### highestLayer

    public int highestLayer()
    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

  - ### lowestLayer

    public int lowestLayer()
    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

  - ### getComponentCountInLayer

    public int getComponentCountInLayer(int layer)
    Returns the number of children currently in the specified layer.
    Parameters:
      `layer` - an int specifying the layer to check
    Returns:
      an int specifying the number of components in that layer

  - ### getComponentsInLayer

    public Component[] getComponentsInLayer(int layer)
    Returns an array of the components in the specified layer.
    Parameters:
      `layer` - an int specifying the layer to check
    Returns:
      an array of Components contained in that layer

  - ### paint

    public void paint(Graphics g)
    Paints this JLayeredPane within the specified graphics context.
    Overrides:
      `paint` in class `JComponent`
    Parameters:
      `g` - the Graphics context within which to paint
    See Also:
      - `JComponent.paintComponent(Graphics)`
      - `JComponent.paintBorder(Graphics)`
      - `JComponent.paintChildren(Graphics)`
      - `JComponent.getComponentGraphics(Graphics)`
      - `JComponent.repaint(long, int, int, int, int)`

  - ### getComponentToLayer

    protected Hashtable<Component, Integer> getComponentToLayer()
    Returns the hashtable that maps components to layers.
    Returns:
      the Hashtable used to map components to their layers

  - ### getObjectForLayer

    protected Integer getObjectForLayer(int layer)
    Returns the Integer object associated with a specified layer.
    Parameters:
      `layer` - an int specifying the layer
    Returns:
      an Integer object for that layer

  - ### insertIndexForLayer

    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.
    Parameters:
      `layer` - an int specifying the layer
      `position` - an int specifying the position within the layer
    Returns:
      an int giving the (absolute) insertion-index
    See Also:
      - `getIndexOf(Component)`

  - ### paramString

    protected String paramString()
    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`.
    Overrides:
      `paramString` in class `JComponent`
    Returns:
      a string representation of this JLayeredPane.

  - ### getAccessibleContext

    @BeanProperty(bound=false) public AccessibleContext getAccessibleContext()
    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.
    Specified by:
      `getAccessibleContext` in interface `Accessible`
    Overrides:
      `getAccessibleContext` in class `Component`
    Returns:
      an AccessibleJLayeredPane that serves as the AccessibleContext of this JLayeredPane