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.
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: 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. 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 callinglayeredPaneParent.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, 1awhere 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, 1aCalling add(5z, 5, 2) results in:
5a, 5b, 5z, 5c, 5x, 2a, 2b, 2c, 1aCalling add(3a, 3, 7) results in:
5a, 5b, 5z, 5c, 5x, 3a, 2a, 2b, 2c, 1aUsing 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.
| Modifier and Type | Class and Description |
|---|---|
protected class |
JLayeredPane.AccessibleJLayeredPane This class implements accessibility support for the |
JComponent.AccessibleJComponent Container.AccessibleAWTContainer Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy public static final Integer DEFAULT_LAYER
Convenience object defining the Default layer. Equivalent to new Integer(0).
public static final Integer PALETTE_LAYER
Convenience object defining the Palette layer. Equivalent to new Integer(100).
public static final Integer MODAL_LAYER
Convenience object defining the Modal layer. Equivalent to new Integer(200).
public static final Integer POPUP_LAYER
Convenience object defining the Popup layer. Equivalent to new Integer(300).
public static final Integer DRAG_LAYER
Convenience object defining the Drag layer. Equivalent to new Integer(400).
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 new Integer(-30000).
JFramepublic static final String LAYER_PROPERTY
Bound property
public JLayeredPane()
Create a new JLayeredPane
protected void addImpl(Component comp,
Object constraints,
int index) Description copied from class: Container
Adds the specified component to this container at the specified index. This method also notifies the layout manager to add the component to this container's layout using the specified constraints object via the addLayoutComponent method.
The constraints are defined by the particular layout manager being used. For example, the BorderLayout class defines five constraints: BorderLayout.NORTH, BorderLayout.SOUTH, BorderLayout.EAST, BorderLayout.WEST, and BorderLayout.CENTER.
The GridBagLayout class requires a GridBagConstraints object. Failure to pass the correct type of constraints object results in an IllegalArgumentException.
If the current layout manager implements LayoutManager2, then LayoutManager2.addLayoutComponent(Component,Object) is invoked on it. If the current layout manager does not implement LayoutManager2, and constraints is a String, then LayoutManager.addLayoutComponent(String,Component) is invoked on it.
If the component is not an ancestor of this container and has a non-null parent, it is removed from its current parent before it is added to this container.
This is the method to override if a program needs to track every add request to a container as all other add methods defer to this one. An overriding method should usually include a call to the superclass's version of the method:
super.addImpl(comp, constraints, index)
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 display the added component.
addImpl in class Container
comp - the component to be addedconstraints - an object expressing layout constraints for this componentindex - the position in the container's list at which to insert the component, where -1 means append to the endContainer.add(Component), Container.add(Component, int), Container.add(Component, java.lang.Object), Container.invalidate(), LayoutManager, LayoutManager2
public void remove(int index)
Remove the indexed component from this pane. This is the absolute index, ignoring layers.
remove in class Container
index - an int specifying the component to removegetIndexOf(java.awt.Component)public void removeAll()
Removes all the components from this container.
removeAll in class Container
Container.add(java.awt.Component), Container.remove(int), Container.invalidate()
public boolean isOptimizedDrawingEnabled()
Returns false if components in the pane can overlap, which makes optimized drawing impossible. Otherwise, returns true.
isOptimizedDrawingEnabled in class JComponent
JComponent.isOptimizedDrawingEnabled()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).
c - the JComponent to movelayer - an int specifying the layer to move it tosetLayer(java.awt.Component, int)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().
c - the JComponent to checkpublic 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.
c - the Component to checkJFrame, JRootPane
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.
c - the Component to set the layer forlayer - an int specifying the layer to set, where lower numbers are closer to the bottompublic void setLayer(Component c,
int layer,
int position) Sets the layer attribute for the specified component and also sets its position within that layer.
c - the Component to set the layer forlayer - an int specifying the layer to set, where lower numbers are closer to the bottomposition - an int specifying the position within the layer, where 0 is the topmost position and -1 is the bottommost positionpublic int getLayer(Component c)
Returns the layer attribute for the specified Component.
c - the Component to checkpublic 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.
c - the Component to checkpublic void moveToFront(Component c)
Moves the component to the top of the components in its current layer (position 0).
c - the Component to movesetPosition(Component, int)public void moveToBack(Component c)
Moves the component to the bottom of the components in its current layer (position -1).
c - the Component to movesetPosition(Component, int)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.
c - the Component to moveposition - an int in the range -1..N-1, where N is the number of components in the component's current layerpublic int getPosition(Component c)
Get the relative position of the component within its layer.
c - the Component to checkgetComponentCountInLayer(int)public int highestLayer()
Returns the highest layer value from all current children. Returns 0 if there are no children.
public int lowestLayer()
Returns the lowest layer value from all current children. Returns 0 if there are no children.
public int getComponentCountInLayer(int layer)
Returns the number of children currently in the specified layer.
layer - an int specifying the layer to checkpublic Component[] getComponentsInLayer(int layer)
Returns an array of the components in the specified layer.
layer - an int specifying the layer to checkpublic void paint(Graphics g)
Paints this JLayeredPane within the specified graphics context.
paint in class JComponent
g - the Graphics context within which to paintJComponent.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)
protected Hashtable<Component,Integer> getComponentToLayer()
Returns the hashtable that maps components to layers.
protected Integer getObjectForLayer(int layer)
Returns the Integer object associated with a specified layer.
layer - an int specifying the layerprotected int insertIndexForLayer(int layer,
int position) Primitive method that determines the proper location to insert a new child based on layer and position requests.
layer - an int specifying the layerposition - an int specifying the position within the layergetIndexOf(java.awt.Component)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.
paramString in class JComponent
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.
getAccessibleContext in interface Accessible
getAccessibleContext in class Component
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