Package Summary Overview Summary

### class:JLayer [NONE]
- 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 `AWTEvent`s 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(JFrame.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: `Container.add(java.awt.Component)` `Container.add(String, java.awt.Component)` `Container.add(java.awt.Component, int)` `Container.add(java.awt.Component, Object)` `Container.add(java.awt.Component, Object, int)` using any of 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()`

### constructor:JLayer() [NONE]
- #### 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>)`

### constructor:JLayer(V) [NONE]
- #### 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>)`

### constructor:JLayer(V, javax.swing.plaf.LayerUI) [NONE]
- #### 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`

### method:getView() [NONE]
- #### 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)`

### method:setView(V) [NONE]
- #### 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()`

### method:setUI(javax.swing.plaf.LayerUI) [NONE]
- #### 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`

### method:getUI() [NONE]
- #### getUI
      public LayerUI<? super V> getUI()
Returns the `LayerUI` for this `JLayer`. Returns: the `LayerUI` for this `JLayer`

### method:getGlassPane() [NONE]
- #### 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)`

### method:setGlassPane(javax.swing.JPanel) [NONE]
- #### 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()`

### method:createGlassPane() [NONE]
- #### 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`

### method:setLayout(java.awt.LayoutManager) [NONE]
- #### 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()`

### method:setBorder(javax.swing.border.Border) [NONE]
- #### 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)`

### method:getBorder() [NONE]
- #### 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()`

### method:addImpl(java.awt.Component, java.lang.Object, int) [NONE]
- #### 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)`

### method:remove(java.awt.Component) [NONE]
- #### remove
      public void remove(Component comp)
Removes the specified component from this container. This method also notifies the layout manager to remove the component from this container's layout via the `removeLayoutComponent` method. This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to reflect the changes. Overrides: `remove` in class `Container` Parameters: `comp` - the component to be removed See Also: `Container.add(java.awt.Component)`, `Container.invalidate()`, `Container.validate()`, `Container.remove(int)`

### method:removeAll() [NONE]
- #### removeAll
      public void removeAll()
Removes all the components from this container. This method also notifies the layout manager to remove the components from this container's layout via the `removeLayoutComponent` method. This method changes layout-related information, and therefore, invalidates the component hierarchy. If the container has already been displayed, the hierarchy must be validated thereafter in order to reflect the changes. Overrides: `removeAll` in class `Container` See Also: `Container.add(java.awt.Component)`, `Container.remove(int)`, `Container.invalidate()`

### method:isPaintingOrigin() [NONE]
- #### 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()`

### method:paintImmediately(int, int, int, int) [NONE]
- #### 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()`

### method:imageUpdate(java.awt.Image, int, int, int, int, int) [NONE]
- #### 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)`

### method:paint(java.awt.Graphics) [NONE]
- #### 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)`

### method:paintComponent(java.awt.Graphics) [NONE]
- #### 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`

### method:isOptimizedDrawingEnabled() [NONE]
- #### 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

### method:propertyChange(java.beans.PropertyChangeEvent) [NONE]
- #### propertyChange
      public void propertyChange(PropertyChangeEvent evt)
This method gets called when a bound property is changed. Specified by: `propertyChange` in interface `PropertyChangeListener` Parameters: `evt` - A PropertyChangeEvent object describing the event source and the property that has changed.

### method:setLayerEventMask(long) [NONE]
- #### 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()`

### method:getLayerEventMask() [NONE]
- #### 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`

### method:updateUI() [NONE]
- #### 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)`

### method:getPreferredScrollableViewportSize() [NONE]
- #### getPreferredScrollableViewportSize
      public Dimension getPreferredScrollableViewportSize()
Returns the preferred size of the viewport for a view component. If the view component of this layer implements `Scrollable`, this method delegates its implementation to the view component. Specified by: `getPreferredScrollableViewportSize` in interface `Scrollable` Returns: the preferred size of the viewport for a view component See Also: `Scrollable`

### method:getScrollableBlockIncrement(java.awt.Rectangle, int, int) [NONE]
- #### getScrollableBlockIncrement
      public 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. If the view component of this layer implements `Scrollable`, this method delegates its implementation to the view component. Specified by: `getScrollableBlockIncrement` in interface `Scrollable` Parameters: `visibleRect` - The view area visible within the viewport `orientation` - Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL. `direction` - Less than zero to scroll up/left, greater than zero for down/right. Returns: the "block" increment for scrolling in the specified direction See Also: `Scrollable`

### method:getScrollableTracksViewportHeight() [NONE]
- #### getScrollableTracksViewportHeight
      public 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. If the view component of this layer implements `Scrollable`, this method delegates its implementation to the view component. Specified by: `getScrollableTracksViewportHeight` in interface `Scrollable` Returns: whether the layer should track the height of the viewport See Also: `Scrollable`

### method:getScrollableTracksViewportWidth() [NONE]
- #### getScrollableTracksViewportWidth
      public 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. If the view component of this layer implements `Scrollable`, this method delegates its implementation to the view component. Specified by: `getScrollableTracksViewportWidth` in interface `Scrollable` Returns: whether the layer should track the width of the viewport See Also: `Scrollable`

### method:getScrollableUnitIncrement(java.awt.Rectangle, int, int) [NONE]
- #### getScrollableUnitIncrement
      public 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. Ideally, components should handle a partially exposed row or column by returning the distance required to completely expose the item. Scrolling containers, like `JScrollPane`, will use this method each time the user requests a unit scroll. If the view component of this layer implements `Scrollable`, this method delegates its implementation to the view component. Specified by: `getScrollableUnitIncrement` in interface `Scrollable` Parameters: `visibleRect` - The view area visible within the viewport `orientation` - Either SwingConstants.VERTICAL or SwingConstants.HORIZONTAL. `direction` - Less than zero to scroll up/left, greater than zero for down/right. Returns: The "unit" increment for scrolling in the specified direction. This value should always be positive. See Also: `Scrollable`

### method:addNotify() [NONE]
- #### addNotify
      public void addNotify()
Notifies this component that it now has a parent component. When this method is invoked, the chain of parent components is set up with `KeyboardAction` event listeners. This method is called by the toolkit internally and should not be called directly by programs. Overrides: `addNotify` in class `JComponent` See Also: `JComponent.registerKeyboardAction(java.awt.event.ActionListener, java.lang.String, javax.swing.KeyStroke, int)`

### method:removeNotify() [NONE]
- #### removeNotify
      public void removeNotify()
Notifies this component that it no longer has a parent component. When this method is invoked, any `KeyboardAction`s set up in the the chain of parent components are removed. This method is called by the toolkit internally and should not be called directly by programs. Overrides: `removeNotify` in class `JComponent` See Also: `JComponent.registerKeyboardAction(java.awt.event.ActionListener, java.lang.String, javax.swing.KeyStroke, int)`

### method:doLayout() [NONE]
- #### doLayout
      public void doLayout()
Delegates its functionality to the `LayerUI.doLayout(JLayer)` method, if `LayerUI` is set. Overrides: `doLayout` in class `Container` See Also: `LayoutManager.layoutContainer(java.awt.Container)`, `Container.setLayout(java.awt.LayoutManager)`, `Container.validate()`

### method:getAccessibleContext() [NONE]
- #### getAccessibleContext
      public AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this `JLayer`. Specified by: `getAccessibleContext` in interface `Accessible` Overrides: `getAccessibleContext` in class `Component` Returns: the AccessibleContext associated with this `JLayer`.