Class SortingFocusTraversalPolicy

public class SortingFocusTraversalPolicy
extends InternalFrameFocusTraversalPolicy

A FocusTraversalPolicy that determines traversal order by sorting the Components of a focus traversal cycle based on a given Comparator. Portions of the Component hierarchy that are not visible and displayable will not be included.

By default, SortingFocusTraversalPolicy implicitly transfers focus down- cycle. That is, during normal focus traversal, the Component traversed after a focus cycle root will be the focus-cycle-root's default Component to focus. This behavior can be disabled using the setImplicitDownCycleTraversal method.

By default, methods of this class with return a Component only if it is visible, displayable, enabled, and focusable. Subclasses can modify this behavior by overriding the accept method.

This policy takes into account focus traversal policy providers. When searching for first/last/next/previous Component, if a focus traversal policy provider is encountered, its focus traversal policy is used to perform the search operation.

Constructors

SortingFocusTraversalPolicy

protected SortingFocusTraversalPolicy()

Constructs a SortingFocusTraversalPolicy without a Comparator. Subclasses must set the Comparator using setComparator before installing this FocusTraversalPolicy on a focus cycle root or KeyboardFocusManager.

SortingFocusTraversalPolicy

public SortingFocusTraversalPolicy(Comparator<? super Component> comparator)

Constructs a SortingFocusTraversalPolicy with the specified Comparator.

Methods

getComponentAfter

public Component getComponentAfter(Container aContainer,
                                   Component aComponent)

Specified by:

getComponentAfter in class FocusTraversalPolicy

Parameters:

aContainer - a focus cycle root of aComponent or a focus traversal policy provider

aComponent - a (possibly indirect) child of aContainer, or aContainer itself

Returns:

the Component that should receive the focus after aComponent, or null if no suitable Component can be found

Throws:

IllegalArgumentException - if aContainer is not a focus cycle root of aComponent or a focus traversal policy provider, or if either aContainer or aComponent is null

getComponentBefore

public Component getComponentBefore(Container aContainer,
                                    Component aComponent)

Specified by:

getComponentBefore in class FocusTraversalPolicy

Parameters:

aContainer - a focus cycle root of aComponent or a focus traversal policy provider

aComponent - a (possibly indirect) child of aContainer, or aContainer itself

Returns:

the Component that should receive the focus before aComponent, or null if no suitable Component can be found

Throws:

IllegalArgumentException - if aContainer is not a focus cycle root of aComponent or a focus traversal policy provider, or if either aContainer or aComponent is null

getFirstComponent

public Component getFirstComponent(Container aContainer)

Returns the first Component in the traversal cycle. This method is used to determine the next Component to focus when traversal wraps in the forward direction.

Specified by:

getFirstComponent in class FocusTraversalPolicy

Parameters:

aContainer - a focus cycle root of aComponent or a focus traversal policy provider whose first Component is to be returned

Returns:

the first Component in the traversal cycle of aContainer, or null if no suitable Component can be found

Throws:

IllegalArgumentException - if aContainer is null

getLastComponent

public Component getLastComponent(Container aContainer)

Returns the last Component in the traversal cycle. This method is used to determine the next Component to focus when traversal wraps in the reverse direction.

Specified by:

getLastComponent in class FocusTraversalPolicy

Parameters:

aContainer - a focus cycle root of aComponent or a focus traversal policy provider whose last Component is to be returned

Returns:

the last Component in the traversal cycle of aContainer, or null if no suitable Component can be found

Throws:

IllegalArgumentException - if aContainer is null

getDefaultComponent

public Component getDefaultComponent(Container aContainer)

Returns the default Component to focus. This Component will be the first to receive focus when traversing down into a new focus traversal cycle rooted at aContainer. The default implementation of this method returns the same Component as getFirstComponent.

Specified by:

getDefaultComponent in class FocusTraversalPolicy

Parameters:

aContainer - a focus cycle root of aComponent or a focus traversal policy provider whose default Component is to be returned

Returns:

the default Component in the traversal cycle of aContainer, or null if no suitable Component can be found

Throws:

IllegalArgumentException - if aContainer is null

See Also:

getFirstComponent(java.awt.Container)

setImplicitDownCycleTraversal

public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)

Sets whether this SortingFocusTraversalPolicy transfers focus down-cycle implicitly. If true, during normal focus traversal, the Component traversed after a focus cycle root will be the focus- cycle-root's default Component to focus. If false, the next Component in the focus traversal cycle rooted at the specified focus cycle root will be traversed instead. The default value for this property is true.

Parameters:

implicitDownCycleTraversal - whether this SortingFocusTraversalPolicy transfers focus down-cycle implicitly

See Also:

getImplicitDownCycleTraversal(), getFirstComponent(java.awt.Container)

getImplicitDownCycleTraversal

public boolean getImplicitDownCycleTraversal()

Returns whether this SortingFocusTraversalPolicy transfers focus down- cycle implicitly. If true, during normal focus traversal, the Component traversed after a focus cycle root will be the focus-cycle-root's default Component to focus. If false, the next Component in the focus traversal cycle rooted at the specified focus cycle root will be traversed instead.

Returns:

whether this SortingFocusTraversalPolicy transfers focus down- cycle implicitly

See Also:

setImplicitDownCycleTraversal(boolean), getFirstComponent(java.awt.Container)

setComparator

protected void setComparator(Comparator<? super Component> comparator)

Sets the Comparator which will be used to sort the Components in a focus traversal cycle.

Parameters:

comparator - the Comparator which will be used for sorting

getComparator

protected Comparator<? super Component> getComparator()

Returns the Comparator which will be used to sort the Components in a focus traversal cycle.

Returns:

the Comparator which will be used for sorting

accept

protected boolean accept(Component aComponent)

Determines whether a Component is an acceptable choice as the new focus owner. By default, this method will accept a Component if and only if it is visible, displayable, enabled, and focusable.

Parameters:

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

Returns:

true if aComponent is visible, displayable, enabled, and focusable; false otherwise