Class DefaultFocusTraversalPolicy

java.lang.Object

java.awt.FocusTraversalPolicy

java.awt.ContainerOrderFocusTraversalPolicy

java.awt.DefaultFocusTraversalPolicy

All Implemented Interfaces:

Serializable

public class DefaultFocusTraversalPolicy
extends ContainerOrderFocusTraversalPolicy

A FocusTraversalPolicy that determines traversal order based on the order of child Components in a Container. From a particular focus cycle root, the policy makes a pre-order traversal of the Component hierarchy, and traverses a Container's children according to the ordering of the array returned by Container.getComponents(). Portions of the hierarchy that are not visible and displayable will not be searched.

If client code has explicitly set the focusability of a Component by either overriding Component.isFocusTraversable() or Component.isFocusable(), or by calling Component.setFocusable(), then a DefaultFocusTraversalPolicy behaves exactly like a ContainerOrderFocusTraversalPolicy. If, however, the Component is relying on default focusability, then a DefaultFocusTraversalPolicy will reject all Components with non-focusable peers. This is the default FocusTraversalPolicy for all AWT Containers.

The focusability of a peer is implementation-dependent. Sun recommends that all implementations for a particular native platform construct peers with the same focusability. The recommendations for Windows and Unix are that Canvases, Labels, Panels, Scrollbars, ScrollPanes, Windows, and lightweight Components have non-focusable peers, and all other Components have focusable peers. These recommendations are used in the Sun AWT implementations. Note that the focusability of a Component's peer is different from, and does not impact, the focusability of the Component itself.

Please see How to Use the Focus Subsystem, a section in The Java Tutorial, and the Focus Specification for more information.

Since:

1.4

See Also:

• Container.getComponents()
• Component.isFocusable()
• Component.setFocusable(boolean)
• Serialized Form

Constructor Summary

Constructors

Constructor	Description
DefaultFocusTraversalPolicy()	Constructs a DefaultFocusTraversalPolicy.

Method Summary

Modifier and Type	Method	Description
protected boolean	accept(Component aComponent)	Determines whether a Component is an acceptable choice as the new focus owner.

Methods declared in class ContainerOrderFocusTraversalPolicy

getComponentAfter, getComponentBefore, getDefaultComponent, getFirstComponent, getImplicitDownCycleTraversal, getLastComponent, setImplicitDownCycleTraversal

Modifier and Type	Method	Description
Component	getComponentAfter(Container aContainer, Component aComponent)	Returns the Component that should receive the focus after aComponent. aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.
Component	getComponentBefore(Container aContainer, Component aComponent)	Returns the Component that should receive the focus before aComponent. aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.
Component	getDefaultComponent(Container aContainer)	Returns the default Component to focus.
Component	getFirstComponent(Container aContainer)	Returns the first Component in the traversal cycle.
boolean	getImplicitDownCycleTraversal()	Returns whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly.
Component	getLastComponent(Container aContainer)	Returns the last Component in the traversal cycle.
void	setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)	Sets whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly.

Methods declared in class FocusTraversalPolicy

getInitialComponent

Modifier and Type	Method	Description
Component	getInitialComponent(Window window)	Returns the Component that should receive the focus when a Window is made visible for the first time.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

DefaultFocusTraversalPolicy

public DefaultFocusTraversalPolicy()

Constructs a DefaultFocusTraversalPolicy.

Method Details

accept

protected boolean accept(Component aComponent)

Determines whether a Component is an acceptable choice as the new focus owner. The Component must be visible, displayable, and enabled to be accepted. If client code has explicitly set the focusability of the Component by either overriding Component.isFocusTraversable() or Component.isFocusable(), or by calling Component.setFocusable(), then the Component will be accepted if and only if it is focusable. If, however, the Component is relying on default focusability, then all Canvases, Labels, Panels, Scrollbars, ScrollPanes, Windows, and lightweight Components will be rejected.

Overrides:

accept in class ContainerOrderFocusTraversalPolicy

Parameters:

aComponent - the Component whose fitness as a focus owner is to be tested

Returns:

true if aComponent meets the above requirements; false otherwise