java.awt

Class Container

java.lang.Object

java.awt.Component

java.awt.Container

All Implemented Interfaces:

ImageObserver, Serializable

Direct Known Subclasses:

HContainer, HScene, Window

public class Container
extends Component

A generic Abstract Window Toolkit(AWT) container object is a component that can contain other AWT components.

Components added to a container are tracked in a list. The order of the list will define the components' front-to-back stacking order within the container. If no index is specified when adding a component to a container, it will be added to the end of the list (and hence to the bottom of the stacking order).

Since:

JDK1.0

Version:

1.239, 02/26/03

Author:

Arthur van Hoff, Sami Shaio

See Also:

add(java.awt.Component, int), getComponent(int), LayoutManager, Serialized Form

Field Summary

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

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

Constructor Summary

Constructors

Constructor and Description
Container() Constructs a new Container.

Method Summary

Methods

Modifier and Type	Method and Description
Component	add(Component comp) Appends the specified component to the end of this container.
Component	add(Component comp, int index) Adds the specified component to this container at the given position.
void	add(Component comp, Object constraints) Adds the specified component to the end of this container.
void	add(Component comp, Object constraints, int index) Adds the specified component to this container with the specified constraints at the specified index.
Component	add(String name, Component comp) Adds the specified component to this container.
void	addContainerListener(ContainerListener l) Adds the specified container listener to receive container events from this container.
protected void	addImpl(Component comp, Object constraints, int index) Adds the specified component to this container at the specified index.
boolean	areFocusTraversalKeysSet(int id) Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Container.
void	doLayout() Causes this container to lay out its components.
Component	findComponentAt(int x, int y) Locates the visible child component that contains the specified position.
Component	findComponentAt(Point p) Locates the visible child component that contains the specified point.
float	getAlignmentX() Returns the alignment along the x axis.
float	getAlignmentY() Returns the alignment along the y axis.
Component	getComponent(int n) Gets the nth component in this container.
Component	getComponentAt(int x, int y) Locates the component that contains the x,y position.
Component	getComponentAt(Point p) Gets the component that contains the specified point.
int	getComponentCount() Gets the number of components in this panel.
Component[]	getComponents() Gets all the components in this container.
ContainerListener[]	getContainerListeners() Returns an array of all the container listeners registered on this container.
Set	getFocusTraversalKeys(int id) Returns the Set of focus traversal keys for a given traversal operation for this Container.
FocusTraversalPolicy	getFocusTraversalPolicy() Returns the focus traversal policy that will manage keyboard traversal of this Container's children, or null if this Container is not a focus cycle root.
Insets	getInsets() Determines the insets of this container, which indicate the size of the container's border.
LayoutManager	getLayout() Gets the layout manager for this container.
Dimension	getMaximumSize() Returns the maximum size of this container.
Dimension	getMinimumSize() Returns the minimum size of this container.
Dimension	getPreferredSize() Returns the preferred size of this container.
void	invalidate() Invalidates the container.
boolean	isAncestorOf(Component c) Checks if the component is contained in the component hierarchy of this container.
boolean	isFocusCycleRoot() Returns whether this Container is the root of a focus traversal cycle.
boolean	isFocusCycleRoot(Container container) Returns whether the specified Container is the focus cycle root of this Container's focus traversal cycle.
boolean	isFocusTraversalPolicySet() Returns whether the focus traversal policy has been explicitly set for this Container.
void	list(PrintStream out, int indent) Prints a listing of this container to the specified output stream.
void	list(PrintWriter out, int indent) Prints out a list, starting at the specified indention, to the specified print writer.
void	paint(Graphics g) Paints the container.
void	paintComponents(Graphics g) Paints each of the components in this container.
protected String	paramString() Returns a string representing the state of this Container.
void	print(Graphics g) Prints the container.
void	printComponents(Graphics g) Prints each of the components in this container.
protected void	processContainerEvent(ContainerEvent e) Processes container events occurring on this container by dispatching them to any registered ContainerListener objects.
protected void	processEvent(AWTEvent e) Processes events on this container.
void	remove(Component comp) Removes the specified component from this container.
void	remove(int index) Removes the component, specified by index, from this container.
void	removeAll() Removes all the components from this container.
void	removeContainerListener(ContainerListener l) Removes the specified container listener so it no longer receives container events from this container.
void	setFocusCycleRoot(boolean focusCycleRoot) Sets whether this Container is the root of a focus traversal cycle.
void	setFocusTraversalKeys(int id, Set keystrokes) Sets the focus traversal keys for a given traversal operation for this Container.
void	setFocusTraversalPolicy(FocusTraversalPolicy policy) Sets the focus traversal policy that will manage keyboard traversal of this Container's children, if this Container is a focus cycle root.
void	setFont(Font f) Sets the font of this container.
void	setLayout(LayoutManager mgr) Sets the layout manager for this container.
void	transferFocusBackward() Transfers the focus to the previous component, as though this Component were the focus owner.
void	transferFocusDownCycle() Transfers the focus down one focus traversal cycle.
void	update(Graphics g) Updates the container.
void	validate() Validates this container and all of its subcomponents.
protected void	validateTree() Recursively descends the container tree and recomputes the layout for any subtrees marked as needing it (those marked as invalid).

Methods inherited from class java.awt.Component

addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, addNotify, addPropertyChangeListener, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enableEvents, enableInputMethods, firePropertyChange, getBackground, getBounds, getBounds, getColorModel, getComponentListeners, getCursor, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMouseWheelListeners, getName, getParent, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, hasFocus, imageUpdate, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isOpaque, isShowing, isValid, isVisible, list, list, list, paintAll, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removeNotify, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, setBackground, setBounds, setBounds, setCursor, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, toString, transferFocus, transferFocusUpCycle

Methods inherited from class java.lang.Object

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

Constructor Detail

Container

public Container()

Constructs a new Container. Containers can be extended directly, but are lightweight in this case and must be contained by a parent somewhere higher up in the component tree that is native. (such as Frame for example).

Method Detail

getComponentCount

public int getComponentCount()

Gets the number of components in this panel.

Returns:

the number of components in this panel.

Since:

JDK1.1

See Also:

getComponent(int)

getComponent

public Component getComponent(int n)

Gets the nth component in this container.

Parameters:

n - the index of the component to get.

Returns:

the n^th component in this container.

Throws:

ArrayIndexOutOfBoundsException - if the n^th value does not exist.

getComponents

public Component[] getComponents()

Gets all the components in this container.

Returns:

an array of all the components in this container.

getInsets

public Insets getInsets()

Determines the insets of this container, which indicate the size of the container's border.

A Frame object, for example, has a top inset that corresponds to the height of the frame's title bar.

Returns:

the insets of this container.

Since:

JDK1.1

See Also:

Insets, LayoutManager

add

public Component add(Component comp)

Appends the specified component to the end of this container. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

Returns:

the component argument

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate()

add

public Component add(String name,
            Component comp)

Adds the specified component to this container. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

This method is obsolete as of 1.1. Please use the method add(Component, Object) instead.

See Also:

add(Component, Object)

add

public Component add(Component comp,
            int index)

Adds the specified component to this container at the given position. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

index - the position at which to insert the component, or -1 to append the component to the end

Returns:

the component comp

See Also:

addImpl(java.awt.Component, java.lang.Object, int), remove(int), validate()

add

public void add(Component comp,
       Object constraints)

Adds the specified component to the end of this container. Also notifies the layout manager to add the component to this container's layout using the specified constraints object. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

constraints - an object expressing layout contraints for this component

Since:

JDK1.1

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate(), LayoutManager

add

public void add(Component comp,
       Object constraints,
       int index)

Adds the specified component to this container with the specified constraints at the specified index. Also notifies the layout manager to add the component to the this container's layout using the specified constraints object. This is a convenience method for addImpl(java.awt.Component, java.lang.Object, int).

Note: If a component has been added to a container that has been displayed, validate must be called on that container to display the new component. If multiple components are being added, you can improve efficiency by calling validate only once, after all the components have been added.

Parameters:

comp - the component to be added

constraints - an object expressing layout contraints for this

index - the position in the container's list at which to insert the component; -1 means insert at the end component

See Also:

addImpl(java.awt.Component, java.lang.Object, int), validate(), remove(int), LayoutManager

addImpl

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

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.

Note that if the component already exists in this container or a child of this container, it is removed from that container before being 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)

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:

IllegalArgumentException - if index is invalid

IllegalArgumentException - if adding the container's parent to itself

IllegalArgumentException - if adding a window to a container

Since:

JDK1.1

See Also:

add(Component), add(Component, int), add(Component, java.lang.Object), LayoutManager, LayoutManager2

remove

public void remove(int index)

Removes the component, specified by index, from this container.

Parameters:

index - the index of the component to be removed.

Since:

JDK1.1

See Also:

add(java.awt.Component)

remove

public void remove(Component comp)

Removes the specified component from this container.

Parameters:

comp - the component to be removed

See Also:

add(java.awt.Component)

removeAll

public void removeAll()

Removes all the components from this container.

See Also:

add(java.awt.Component), remove(int)

getLayout

public LayoutManager getLayout()

Gets the layout manager for this container.

See Also:

doLayout(), setLayout(java.awt.LayoutManager)

setLayout

public void setLayout(LayoutManager mgr)

Sets the layout manager for this container.

Parameters:

mgr - the specified layout manager

See Also:

doLayout(), getLayout()

doLayout

public void doLayout()

Causes this container to lay out its components. Most programs should not call this method directly, but should invoke the validate method instead.

Overrides:

doLayout in class Component

Since:

JDK1.1

See Also:

LayoutManager.layoutContainer(java.awt.Container), setLayout(java.awt.LayoutManager), validate()

invalidate

public void invalidate()

Invalidates the container. The container and all parents above it are marked as needing to be laid out. This method can be called often, so it needs to execute quickly.

Overrides:

invalidate in class Component

See Also:

validate(), LayoutManager

validate

public void validate()

Validates this container and all of its subcomponents.

The validate method is used to cause a container to lay out its subcomponents again. It should be invoked when this container's subcomponents are modified (added to or removed from the container, or layout-related information changed) after the container has been displayed.

Overrides:

validate in class Component

See Also:

add(java.awt.Component), Component.invalidate()

validateTree

protected void validateTree()

Recursively descends the container tree and recomputes the layout for any subtrees marked as needing it (those marked as invalid). Synchronization should be provided by the method that calls this one: validate.

setFont

public void setFont(Font f)

Sets the font of this container.

Overrides:

setFont in class Component

Parameters:

f - The font to become this container's font.

Since:

JDK1.0

See Also:

Component.getFont()

getPreferredSize

public Dimension getPreferredSize()

Returns the preferred size of this container.

Overrides:

getPreferredSize in class Component

Returns:

an instance of Dimension that represents the preferred size of this container.

See Also:

getMinimumSize(), getLayout(), LayoutManager.preferredLayoutSize(Container), Component.getPreferredSize()

getMinimumSize

public Dimension getMinimumSize()

Returns the minimum size of this container.

Overrides:

getMinimumSize in class Component

Returns:

an instance of Dimension that represents the minimum size of this container.

Since:

JDK1.1

See Also:

getPreferredSize(), getLayout(), LayoutManager.minimumLayoutSize(Container), Component.getMinimumSize()

getMaximumSize

public Dimension getMaximumSize()

Returns the maximum size of this container.

Overrides:

getMaximumSize in class Component

Returns:

a dimension object indicating this component's maximum size

See Also:

getPreferredSize()

getAlignmentX

public float getAlignmentX()

Returns the alignment along the x axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.

Overrides:

getAlignmentX in class Component

getAlignmentY

public float getAlignmentY()

Returns the alignment along the y axis. This specifies how the component would like to be aligned relative to other components. The value should be a number between 0 and 1 where 0 represents alignment along the origin, 1 is aligned the furthest away from the origin, 0.5 is centered, etc.

Overrides:

getAlignmentY in class Component

paint

public void paint(Graphics g)

Paints the container. This forwards the paint to any lightweight components that are children of this container. If this method is reimplemented, super.paint(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, paint() will not be forwarded to that child.

Overrides:

paint in class Component

Parameters:

g - the specified Graphics window

See Also:

Component.update(Graphics)

update

public void update(Graphics g)

Updates the container. This forwards the update to any lightweight components that are children of this container. If this method is reimplemented, super.update(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, update() will not be forwarded to that child.

Overrides:

update in class Component

Parameters:

g - the specified Graphics window

See Also:

Component.update(Graphics)

print

public void print(Graphics g)

Prints the container. This forwards the print to any lightweight components that are children of this container. If this method is reimplemented, super.print(g) should be called so that lightweight components are properly rendered. If a child component is entirely clipped by the current clipping setting in g, print() will not be forwarded to that child.

Overrides:

print in class Component

Parameters:

g - the specified Graphics window

See Also:

Component.update(Graphics)

paintComponents

public void paintComponents(Graphics g)

Paints each of the components in this container.

Parameters:

g - the graphics context.

See Also:

Component.paint(java.awt.Graphics), Component.paintAll(java.awt.Graphics)

printComponents

public void printComponents(Graphics g)

Prints each of the components in this container.

Parameters:

g - the graphics context.

See Also:

Component.print(java.awt.Graphics), Component.printAll(java.awt.Graphics)

addContainerListener

public void addContainerListener(ContainerListener l)

Adds the specified container listener to receive container events from this container. If l is null, no exception is thrown and no action is performed.

Parameters:

l - the container listener

See Also:

removeContainerListener(java.awt.event.ContainerListener)

removeContainerListener

public void removeContainerListener(ContainerListener l)

Removes the specified container listener so it no longer receives container events from this container. If l is null, no exception is thrown and no action is performed.

Parameters:

l - the container listener

See Also:

addContainerListener(java.awt.event.ContainerListener)

getContainerListeners

public ContainerListener[] getContainerListeners()

Returns an array of all the container listeners registered on this container.

Returns:

all of this container's ContainerListeners or an empty array if no container listeners are currently registered

Since:

1.4

See Also:

addContainerListener(java.awt.event.ContainerListener), removeContainerListener(java.awt.event.ContainerListener)

processEvent

protected void processEvent(AWTEvent e)

Processes events on this container. If the event is a ContainerEvent, it invokes the processContainerEvent method, else it invokes its superclass's processEvent.

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Overrides:

processEvent in class Component

Parameters:

e - the event

See Also:

Component.processComponentEvent(java.awt.event.ComponentEvent), Component.processFocusEvent(java.awt.event.FocusEvent), Component.processKeyEvent(java.awt.event.KeyEvent), Component.processMouseEvent(java.awt.event.MouseEvent), Component.processMouseMotionEvent(java.awt.event.MouseEvent), Component.processInputMethodEvent(java.awt.event.InputMethodEvent), Component.processMouseWheelEvent(java.awt.event.MouseWheelEvent)

processContainerEvent

protected void processContainerEvent(ContainerEvent e)

Processes container events occurring on this container by dispatching them to any registered ContainerListener objects. NOTE: This method will not be called unless container events are enabled for this component; this happens when one of the following occurs:

• A ContainerListener object is registered via addContainerListener
• Container events are enabled via enableEvents

Note that if the event parameter is null the behavior is unspecified and may result in an exception.

Parameters:

e - the container event

See Also:

Component.enableEvents(long)

getComponentAt

public Component getComponentAt(int x,
                       int y)

Locates the component that contains the x,y position. The top-most child component is returned in the case where there is overlap in the components. This is determined by finding the component closest to the index 0 that claims to contain the given point via Component.contains(), except that Components which have native peers take precedence over those which do not (i.e., lightweight Components).

Overrides:

getComponentAt in class Component

Parameters:

x - the x coordinate

y - the y coordinate

Returns:

null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned; otherwise the top-most child is returned.

Since:

JDK1.1

See Also:

Component.contains(int, int)

getComponentAt

public Component getComponentAt(Point p)

Gets the component that contains the specified point.

Overrides:

getComponentAt in class Component

Parameters:

p - the point.

Returns:

returns the component that contains the point, or null if the component does not contain the point.

Since:

JDK1.1

See Also:

Component.contains(int, int)

findComponentAt

public Component findComponentAt(int x,
                        int y)

Locates the visible child component that contains the specified position. The top-most child component is returned in the case where there is overlap in the components. If the containing child component is a Container, this method will continue searching for the deepest nested child component. Components which are not visible are ignored during the search.

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.

Parameters:

x - the x coordinate

y - the y coordinate

Returns:

null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.

Since:

1.2

See Also:

Component.contains(int, int), getComponentAt(int, int)

findComponentAt

public Component findComponentAt(Point p)

Locates the visible child component that contains the specified point. The top-most child component is returned in the case where there is overlap in the components. If the containing child component is a Container, this method will continue searching for the deepest nested child component. Components which are not visible are ignored during the search.

The findComponentAt method is different from getComponentAt in that getComponentAt only searches the Container's immediate children; if the containing component is a Container, findComponentAt will search that child to find a nested component.

Parameters:

p - the point.

Returns:

null if the component does not contain the position. If there is no child component at the requested point and the point is within the bounds of the container the container itself is returned.

Since:

1.2

See Also:

Component.contains(int, int), getComponentAt(int, int)

isAncestorOf

public boolean isAncestorOf(Component c)

Checks if the component is contained in the component hierarchy of this container.

Parameters:

c - the component

Returns:

true if it is an ancestor; false otherwise.

Since:

JDK1.1

paramString

protected String paramString()

Returns a string representing the state of this Container. 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 Component

Returns:

the parameter string of this container

list

public void list(PrintStream out,
        int indent)

Prints a listing of this container to the specified output stream. The listing starts at the specified indentation.

Overrides:

list in class Component

Parameters:

out - a print stream.

indent - the number of spaces to indent.

Since:

JDK1.0

See Also:

Component.list(java.io.PrintStream, int)

list

public void list(PrintWriter out,
        int indent)

Prints out a list, starting at the specified indention, to the specified print writer.

Overrides:

list in class Component

Parameters:

out - the print writer to print to

indent - the number of spaces to indent

See Also:

PrintStream.println(java.lang.Object)

setFocusTraversalKeys

public void setFocusTraversalKeys(int id,
                         Set keystrokes)

Sets the focus traversal keys for a given traversal operation for this Container.

The default values for a Container's focus traversal keys are implementation-dependent. Sun recommends that all implementations for a particular native platform use the same default values. The recommendations for Windows and Unix are listed below. These recommendations are used in the Sun AWT implementations.

Identifier	Meaning	Default
KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS	Normal forward keyboard traversal	TAB on KEY_PRESSED, CTRL-TAB on KEY_PRESSED
KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS	Normal reverse keyboard traversal	SHIFT-TAB on KEY_PRESSED, CTRL-SHIFT-TAB on KEY_PRESSED
KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS	Go up one focus traversal cycle	none
KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS		Go down one focus traversal cycle	none

To disable a traversal key, use an empty Set; Collections.EMPTY_SET is recommended.

Using the AWTKeyStroke API, client code can specify on which of two specific KeyEvents, KEY_PRESSED or KEY_RELEASED, the focus traversal operation will occur. Regardless of which KeyEvent is specified, however, all KeyEvents related to the focus traversal key, including the associated KEY_TYPED event, will be consumed, and will not be dispatched to any Container. It is a runtime error to specify a KEY_TYPED event as mapping to a focus traversal operation, or to map the same event to multiple default focus traversal operations.

If a value of null is specified for the Set, this Container inherits the Set from its parent. If all ancestors of this Container have null specified for the Set, then the current KeyboardFocusManager's default Set is used.

Overrides:

setFocusTraversalKeys in class Component

Parameters:

id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

keystrokes - the Set of AWTKeyStroke for the specified operation

Throws:

IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS, or if keystrokes contains null, or if any Object in keystrokes is not an AWTKeyStroke, or if any keystroke represents a KEY_TYPED event, or if any keystroke already maps to another focus traversal operation for this Container

Since:

1.4

See Also:

getFocusTraversalKeys(int), KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

getFocusTraversalKeys

public Set getFocusTraversalKeys(int id)

Returns the Set of focus traversal keys for a given traversal operation for this Container. (See setFocusTraversalKeys for a full description of each key.)

If a Set of traversal keys has not been explicitly defined for this Container, then this Container's parent's Set is returned. If no Set has been explicitly defined for any of this Container's ancestors, then the current KeyboardFocusManager's default Set is returned.

Overrides:

getFocusTraversalKeys in class Component

Parameters:

id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

Returns:

the Set of AWTKeyStrokes for the specified operation. The Set will be unmodifiable, and may be empty. null will never be returned.

Throws:

IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

Since:

1.4

See Also:

setFocusTraversalKeys(int, java.util.Set), KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

areFocusTraversalKeysSet

public boolean areFocusTraversalKeysSet(int id)

Returns whether the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Container. If this method returns false, this Container is inheriting the Set from an ancestor, or from the current KeyboardFocusManager.

Overrides:

areFocusTraversalKeysSet in class Component

Parameters:

id - one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

Returns:

true if the the Set of focus traversal keys for the given focus traversal operation has been explicitly defined for this Component; false otherwise.

Throws:

IllegalArgumentException - if id is not one of KeyboardFocusManager.FORWARD_TRAVERSAL_KEYS, KeyboardFocusManager.BACKWARD_TRAVERSAL_KEYS, KeyboardFocusManager.UP_CYCLE_TRAVERSAL_KEYS, or KeyboardFocusManager.DOWN_CYCLE_TRAVERSAL_KEYS

Since:

1.4

isFocusCycleRoot

public boolean isFocusCycleRoot(Container container)

Returns whether the specified Container is the focus cycle root of this Container's focus traversal cycle. Each focus traversal cycle has only a single focus cycle root and each Container which is not a focus cycle root belongs to only a single focus traversal cycle. Containers which are focus cycle roots belong to two cycles: one rooted at the Container itself, and one rooted at the Container's nearest focus-cycle-root ancestor. This method will return true for both such Containers in this case.

Overrides:

isFocusCycleRoot in class Component

Parameters:

container - the Container to be tested

Returns:

true if the specified Container is a focus-cycle- root of this Container; false otherwise

Since:

1.4

See Also:

isFocusCycleRoot()

transferFocusBackward

public void transferFocusBackward()

Description copied from class: Component

Transfers the focus to the previous component, as though this Component were the focus owner.

Overrides:

transferFocusBackward in class Component

See Also:

Component.requestFocus()

setFocusTraversalPolicy

public void setFocusTraversalPolicy(FocusTraversalPolicy policy)

Sets the focus traversal policy that will manage keyboard traversal of this Container's children, if this Container is a focus cycle root. If the argument is null, this Container inherits its policy from its focus- cycle-root ancestor. If the argument is non-null, this policy will be inherited by all focus-cycle-root children that have no keyboard- traversal policy of their own (as will, recursively, their focus-cycle- root children).

If this Container is not a focus cycle root, the policy will be remembered, but will not be used or inherited by this or any other Containers until this Container is made a focus cycle root.

Parameters:

policy - the new focus traversal policy for this Container

Since:

1.4

See Also:

getFocusTraversalPolicy(), setFocusCycleRoot(boolean), isFocusCycleRoot(java.awt.Container)

getFocusTraversalPolicy

public FocusTraversalPolicy getFocusTraversalPolicy()

Returns the focus traversal policy that will manage keyboard traversal of this Container's children, or null if this Container is not a focus cycle root. If no traversal policy has been explicitly set for this Container, then this Container's focus-cycle-root ancestor's policy is returned.

Returns:

this Container's focus traversal policy, or null if this Container is not a focus cycle root.

Since:

1.4

See Also:

setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), setFocusCycleRoot(boolean), isFocusCycleRoot(java.awt.Container)

isFocusTraversalPolicySet

public boolean isFocusTraversalPolicySet()

Returns whether the focus traversal policy has been explicitly set for this Container. If this method returns false, this Container will inherit its focus traversal policy from an ancestor.

Returns:

true if the focus traversal policy has been explicitly set for this Container; false otherwise.

Since:

1.4

setFocusCycleRoot

public void setFocusCycleRoot(boolean focusCycleRoot)

Sets whether this Container is the root of a focus traversal cycle. Once focus enters a traversal cycle, typically it cannot leave it via focus traversal unless one of the up- or down-cycle keys is pressed. Normal traversal is limited to this Container, and all of this Container's descendants that are not descendants of inferior focus cycle roots. Note that a FocusTraversalPolicy may bend these restrictions, however. For example, ContainerOrderFocusTraversalPolicy supports implicit down-cycle traversal.

Parameters:

focusCycleRoot - indicates whether this Container is the root of a focus traversal cycle

Since:

1.4

See Also:

isFocusCycleRoot(), setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), ContainerOrderFocusTraversalPolicy

isFocusCycleRoot

public boolean isFocusCycleRoot()

Returns whether this Container is the root of a focus traversal cycle. Once focus enters a traversal cycle, typically it cannot leave it via focus traversal unless one of the up- or down-cycle keys is pressed. Normal traversal is limited to this Container, and all of this Container's descendants that are not descendants of inferior focus cycle roots. Note that a FocusTraversalPolicy may bend these restrictions, however. For example, ContainerOrderFocusTraversalPolicy supports implicit down-cycle traversal.

Returns:

whether this Container is the root of a focus traversal cycle

Since:

1.4

See Also:

setFocusCycleRoot(boolean), setFocusTraversalPolicy(java.awt.FocusTraversalPolicy), getFocusTraversalPolicy(), ContainerOrderFocusTraversalPolicy

transferFocusDownCycle

public void transferFocusDownCycle()

Transfers the focus down one focus traversal cycle. If this Container is a focus cycle root, then the focus owner is set to this Container's default Component to focus, and the current focus cycle root is set to this Container. If this Container is not a focus cycle root, then no focus traversal operation occurs.

Since:

1.4

See Also:

Component.requestFocus(), isFocusCycleRoot(java.awt.Container), setFocusCycleRoot(boolean)