Class JLayer<V extends Component>

java.lang.Object
- java.awt.Component
- - java.awt.Container
  - - javax.swing.JComponent
    - - javax.swing.JLayer<V>

Type Parameters:: V - the type of JLayer's view component

All Implemented Interfaces:: ImageObserver, MenuContainer, PropertyChangeListener, Serializable, EventListener, Accessible, Scrollable

public final class JLayer<V extends Component>
extends JComponent
implements Scrollable, PropertyChangeListener, Accessible

JLayer is a universal decorator for Swing components which enables you to implement various advanced painting effects as well as receive notifications of all AWTEvents generated within its borders.

JLayer delegates the handling of painting and input events to a LayerUI object, which performs the actual decoration.

The custom painting implemented in the LayerUI and events notification work for the JLayer itself and all its subcomponents. This combination enables you to enrich existing components by adding new advanced functionality such as temporary locking of a hierarchy, data tips for compound components, enhanced mouse scrolling etc and so on.

JLayer is a good solution if you only need to do custom painting over compound component or catch input events from its subcomponents.

import javax.swing.*;
 import javax.swing.plaf.LayerUI;
 import java.awt.*;

 public class JLayerSample {

     private static JLayer<JComponent> createLayer() {
         // This custom layerUI will fill the layer with translucent green
         // and print out all mouseMotion events generated within its borders
         LayerUI<JComponent> layerUI = new LayerUI<JComponent>() {

             public void paint(Graphics g, JComponent c) {
                 // paint the layer as is
                 super.paint(g, c);
                 // fill it with the translucent green
                 g.setColor(new Color(0, 128, 0, 128));
                 g.fillRect(0, 0, c.getWidth(), c.getHeight());
             }

             public void installUI(JComponent c) {
                 super.installUI(c);
                 // enable mouse motion events for the layer's subcomponents
                 ((JLayer) c).setLayerEventMask(AWTEvent.MOUSE_MOTION_EVENT_MASK);
             }

             public void uninstallUI(JComponent c) {
                 super.uninstallUI(c);
                 // reset the layer event mask
                 ((JLayer) c).setLayerEventMask(0);
             }

             // overridden method which catches MouseMotion events
             public void eventDispatched(AWTEvent e, JLayer<? extends JComponent> l) {
                 System.out.println("AWTEvent detected: " + e);
             }
         };
         // create a component to be decorated with the layer
         JPanel panel = new JPanel();
         panel.add(new JButton("JButton"));

         // create the layer for the panel using our custom layerUI
         return new JLayer<JComponent>(panel, layerUI);
     }

     private static void createAndShowGUI() {
         final JFrame frame = new JFrame();
         frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

         // work with the layer as with any other Swing component
         frame.add(createLayer());

         frame.setSize(200, 200);
         frame.setLocationRelativeTo(null);
         frame.setVisible(true);
     }

     public static void main(String[] args) throws Exception {
         SwingUtilities.invokeAndWait(new Runnable() {
             public void run() {
                 createAndShowGUI();
             }
         });
     }
 }

Note: JLayer doesn't support the following methods:

using any of them will cause UnsupportedOperationException to be thrown, to add a component to JLayer use setView(Component) or setGlassPane(JPanel).

Since:: 1.7
See Also:: JLayer(Component), setView(Component), getView(), LayerUI, JLayer(Component, LayerUI), setUI(javax.swing.plaf.LayerUI), getUI(), Serialized Form

Nested Classes

Nested classes/interfaces declared in class javax.swing.JComponent

JComponent.AccessibleJComponent

Nested classes/interfaces declared in class java.awt.Container

Container.AccessibleAWTContainer

Nested classes/interfaces declared in class java.awt.Component

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

Fields

Fields declared in class javax.swing.JComponent

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

Fields declared in class java.awt.Component

accessibleContext, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields declared in interface java.awt.image.ImageObserver

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

Constructors

Constructor	Description
`JLayer()`	Creates a new `JLayer` object with a `null` view component and default `LayerUI`.
`JLayer(V view)`	Creates a new `JLayer` object with default `LayerUI`.
`JLayer(V view, LayerUI<V> ui)`	Creates a new `JLayer` object with the specified view component and `LayerUI` object.

Methods

Modifier and Type	Method	Description
`protected void`	`addImpl(Component comp, Object constraints, int index)`	This method is not supported by `JLayer` and always throws `UnsupportedOperationException`
`JPanel`	`createGlassPane()`	Called by the constructor methods to create a default `glassPane`.
`void`	`doLayout()`	Delegates its functionality to the `LayerUI.doLayout(JLayer)` method, if `LayerUI` is set.
`AccessibleContext`	`getAccessibleContext()`	Gets the AccessibleContext associated with this `JLayer`.
`Border`	`getBorder()`	Delegates its functionality to the `getView().getBorder()` method, if the view component is an instance of `javax.swing.JComponent`, otherwise returns `null`.
`JPanel`	`getGlassPane()`	Returns the `JLayer`'s glassPane component or `null`.
`long`	`getLayerEventMask()`	Returns the bitmap of event mask to receive by this `JLayer` and its `LayerUI`.
`Dimension`	`getPreferredScrollableViewportSize()`	Returns the preferred size of the viewport for a view component.
`int`	`getScrollableBlockIncrement(Rectangle visibleRect, int orientation, int direction)`	Returns a scroll increment, which is required for components that display logical rows or columns in order to completely expose one block of rows or columns, depending on the value of orientation.
`boolean`	`getScrollableTracksViewportHeight()`	Returns `false` to indicate that the height of the viewport does not determine the height of the layer, unless the preferred height of the layer is smaller than the height of the viewport.
`boolean`	`getScrollableTracksViewportWidth()`	Returns `false` to indicate that the width of the viewport does not determine the width of the layer, unless the preferred width of the layer is smaller than the width of the viewport.
`int`	`getScrollableUnitIncrement(Rectangle visibleRect, int orientation, int direction)`	Returns a scroll increment, which is required for components that display logical rows or columns in order to completely expose one new row or column, depending on the value of orientation.
`LayerUI<? super V>`	`getUI()`	Returns the `LayerUI` for this `JLayer`.
`V`	`getView()`	Returns the `JLayer`'s view component or `null`.
`boolean`	`imageUpdate(Image img, int infoflags, int x, int y, int w, int h)`	Delegates its functionality to the `LayerUI.imageUpdate(java.awt.Image, int, int, int, int, int, JLayer)` method, if the `LayerUI` is set.
`boolean`	`isOptimizedDrawingEnabled()`	The `JLayer` overrides the default implementation of this method (in `JComponent`) to return `false`.
`protected boolean`	`isPaintingOrigin()`	Always returns `true` to cause painting to originate from `JLayer`, or one of its ancestors.
`void`	`paint(Graphics g)`	Delegates all painting to the `LayerUI` object.
`protected void`	`paintComponent(Graphics g)`	This method is empty, because all painting is done by `paint(Graphics)` and `ComponentUI.update(Graphics, JComponent)` methods
`void`	`paintImmediately(int x, int y, int w, int h)`	Delegates its functionality to the `LayerUI.paintImmediately(int, int, int, int, JLayer)` method, if `LayerUI` is set.
`void`	`setBorder(Border border)`	Delegates its functionality to the `getView().setBorder(Border)` method, if the view component is an instance of `javax.swing.JComponent`, otherwise this method is a no-op.
`void`	`setGlassPane(JPanel glassPane)`	Sets the `JLayer`'s glassPane component, which can be `null`.
`void`	`setLayerEventMask(long layerEventMask)`	Enables the events from JLayer and all its descendants defined by the specified event mask parameter to be delivered to the `LayerUI.eventDispatched(AWTEvent, JLayer)` method.
`void`	`setLayout(LayoutManager mgr)`	Sets the layout manager for this container.
`void`	`setUI(LayerUI<? super V> ui)`	Sets the `LayerUI` which will perform painting and receive input events for this `JLayer`.
`void`	`setView(V view)`	Sets the `JLayer`'s view component, which can be `null`.
`void`	`updateUI()`	Delegates its functionality to the `LayerUI.updateUI(JLayer)` method, if `LayerUI` is set.

Methods declared in class javax.swing.JComponent

addAncestorListener, addNotify, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, disable, enable, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBaseline, getBaselineResizeBehavior, 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, getUIClassID, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isOpaque, isPaintingForPrint, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paintBorder, paintChildren, paintImmediately, paramString, 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, setComponentPopupMenu, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFocusTraversalKeys, setFont, setForeground, setInheritsPopupMenu, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, unregisterKeyboardAction, update

Methods declared in class java.awt.Container

add, add, add, add, add, addContainerListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, 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, remove, removeAll, removeContainerListener, setComponentZOrder, setFocusCycleRoot, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, transferFocusDownCycle, validate, validateTree

Methods declared in class java.awt.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, hide, 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 java.lang.Object

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

Methods declared in interface java.beans.PropertyChangeListener

propertyChange

Constructors

JLayer

public JLayer()

Creates a new JLayer object with a null view component and default LayerUI.

See Also:: setView(V), setUI(javax.swing.plaf.LayerUI<? super V>)

JLayer

public JLayer(V view)

Creates a new JLayer object with default LayerUI.

Parameters:: view - the component to be decorated by this JLayer
See Also:: setUI(javax.swing.plaf.LayerUI<? super V>)

JLayer

public JLayer(V view,
              LayerUI<V> ui)

Creates a new JLayer object with the specified view component and LayerUI object.

Parameters:: view - the component to be decorated; ui - the LayerUI delegate to be used by this JLayer

Methods

getView

public V getView()

Returns the JLayer's view component or null.
This is a bound property.

Returns:: the JLayer's view component or null if none exists
See Also:: setView(Component)

setView

public void setView(V view)

Sets the JLayer's view component, which can be null.
This is a bound property.

Parameters:: view - the view component for this JLayer
See Also:: getView()

setUI

public void setUI(LayerUI<? super V> ui)

Sets the LayerUI which will perform painting and receive input events for this JLayer.

Parameters:: ui - the LayerUI for this JLayer

getUI

public LayerUI<? super V> getUI()

Returns the LayerUI for this JLayer.

Overrides:: getUI in class JComponent
Returns:: the LayerUI for this JLayer

getGlassPane

public JPanel getGlassPane()

Returns the JLayer's glassPane component or null.
This is a bound property.

Returns:: the JLayer's glassPane component or null if none exists
See Also:: setGlassPane(JPanel)

setGlassPane

public void setGlassPane(JPanel glassPane)

Sets the JLayer's glassPane component, which can be null.
This is a bound property.

Parameters:: glassPane - the glassPane component of this JLayer
See Also:: getGlassPane()

createGlassPane

public JPanel createGlassPane()

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

Returns:: the default glassPane

setLayout

public void setLayout(LayoutManager mgr)

Sets the layout manager for this container. This method is overridden to prevent the layout manager from being set.

Note: If mgr is non-null, this method will throw an exception as layout managers are not supported on a JLayer.

Overrides:: setLayout in class Container
Parameters:: mgr - the specified layout manager
Throws:: IllegalArgumentException - this method is not supported
See Also:: Container.doLayout(), Container.getLayout(), Container.invalidate()

setBorder

public void setBorder(Border border)

Delegates its functionality to the getView().setBorder(Border) method, if the view component is an instance of javax.swing.JComponent, otherwise this method is a no-op.

Overrides:: setBorder in class JComponent
Parameters:: border - the border to be rendered for the view component
See Also:: getView(), JComponent.setBorder(Border)

getBorder

public Border getBorder()

Delegates its functionality to the getView().getBorder() method, if the view component is an instance of javax.swing.JComponent, otherwise returns null.

Overrides:: getBorder in class JComponent
Returns:: the border object for the view component
See Also:: getView(), setBorder(javax.swing.border.Border), JComponent.getBorder()

addImpl

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

This method is not supported by JLayer and always throws UnsupportedOperationException

Overrides:: addImpl in class Container
Parameters:: comp - the component to be added; constraints - an object expressing layout constraints for this component; index - the position in the container's list at which to insert the component, where -1 means append to the end
Throws:: UnsupportedOperationException - this method is not supported
See Also:: setView(Component), setGlassPane(JPanel)

isPaintingOrigin

protected boolean isPaintingOrigin()

Always returns true to cause painting to originate from JLayer, or one of its ancestors.

Overrides:: isPaintingOrigin in class JComponent
Returns:: true
See Also:: JComponent.isPaintingOrigin()

paintImmediately

public void paintImmediately(int x,
                             int y,
                             int w,
                             int h)

Delegates its functionality to the LayerUI.paintImmediately(int, int, int, int, JLayer) method, if LayerUI is set.

Overrides:: paintImmediately in class JComponent
Parameters:: x - the x value of the region to be painted; y - the y value of the region to be painted; w - the width of the region to be painted; h - the height of the region to be painted
See Also:: JComponent.repaint(long, int, int, int, int), JComponent.isPaintingOrigin()

imageUpdate

public boolean imageUpdate(Image img,
                           int infoflags,
                           int x,
                           int y,
                           int w,
                           int h)

Delegates its functionality to the LayerUI.imageUpdate(java.awt.Image, int, int, int, int, int, JLayer) method, if the LayerUI is set.

Specified by:: imageUpdate in interface ImageObserver
Overrides:: imageUpdate in class Component
Parameters:: img - the image being observed; infoflags - see imageUpdate for more information; x - the x coordinate; y - the y coordinate; w - the width; h - the height
Returns:: false if the infoflags indicate that the image is completely loaded; true otherwise.
See Also:: ImageObserver, Graphics.drawImage(Image, int, int, Color, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, int, int, Color, java.awt.image.ImageObserver), Graphics.drawImage(Image, int, int, int, int, java.awt.image.ImageObserver), ImageObserver.imageUpdate(java.awt.Image, int, int, int, int, int)

paint

public void paint(Graphics g)

Delegates all painting to the LayerUI object.

Overrides:: paint in class JComponent
Parameters:: g - the Graphics to render to
See Also:: JComponent.paintComponent(java.awt.Graphics), JComponent.paintBorder(java.awt.Graphics), JComponent.paintChildren(java.awt.Graphics), JComponent.getComponentGraphics(java.awt.Graphics), JComponent.repaint(long, int, int, int, int)

paintComponent

protected void paintComponent(Graphics g)

This method is empty, because all painting is done by paint(Graphics) and ComponentUI.update(Graphics, JComponent) methods

Overrides:: paintComponent in class JComponent
Parameters:: g - the Graphics object to protect
See Also:: JComponent.paint(java.awt.Graphics), ComponentUI

isOptimizedDrawingEnabled

public boolean isOptimizedDrawingEnabled()

The JLayer overrides the default implementation of this method (in JComponent) to return false. This ensures that the drawing machinery will call the JLayer's paint implementation rather than messaging the JLayer's children directly.

Overrides:: isOptimizedDrawingEnabled in class JComponent
Returns:: false

setLayerEventMask

public void setLayerEventMask(long layerEventMask)

Enables the events from JLayer and all its descendants defined by the specified event mask parameter to be delivered to the LayerUI.eventDispatched(AWTEvent, JLayer) method.

Events are delivered provided that LayerUI is set for this JLayer and the JLayer is displayable.

The following example shows how to correctly use this method in the LayerUI implementations:

public void installUI(JComponent c) {
       super.installUI(c);
       JLayer l = (JLayer) c;
       // this LayerUI will receive only key and focus events
       l.setLayerEventMask(AWTEvent.KEY_EVENT_MASK | AWTEvent.FOCUS_EVENT_MASK);
    }

    public void uninstallUI(JComponent c) {
       super.uninstallUI(c);
       JLayer l = (JLayer) c;
       // JLayer must be returned to its initial state
       l.setLayerEventMask(0);
    }

By default JLayer receives no events and its event mask is 0.

Parameters:: layerEventMask - the bitmask of event types to receive
See Also:: getLayerEventMask(), LayerUI.eventDispatched(AWTEvent, JLayer), Component.isDisplayable()

getLayerEventMask

public long getLayerEventMask()

Returns the bitmap of event mask to receive by this JLayer and its LayerUI.

It means that LayerUI.eventDispatched(AWTEvent, JLayer) method will only receive events that match the event mask.

By default JLayer receives no events.

Returns:: the bitmask of event types to receive for this JLayer

updateUI

public void updateUI()

Delegates its functionality to the LayerUI.updateUI(JLayer) method, if LayerUI is set.

Overrides:: updateUI in class JComponent
See Also:: JComponent.setUI(javax.swing.plaf.ComponentUI), UIManager.getLookAndFeel(), UIManager.getUI(javax.swing.JComponent)