# Class SortingFocusTraversalPolicy

java.lang.Object
java.awt.FocusTraversalPolicy
javax.swing.InternalFrameFocusTraversalPolicy
javax.swing.SortingFocusTraversalPolicy

Direct Known Subclasses:
  `LayoutFocusTraversalPolicy`

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.

Since:
  1.4
See Also:
  - `Comparator`

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`SortingFocusTraversalPolicy()`
Constructs a SortingFocusTraversalPolicy without a Comparator.
``
`SortingFocusTraversalPolicy(Comparator<? super Component> comparator)`
Constructs a SortingFocusTraversalPolicy with the specified Comparator.

## 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.
`protected Comparator<? super Component>`
`getComparator()`
Returns the Comparator which will be used to sort the Components in a focus traversal cycle.
`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 SortingFocusTraversalPolicy transfers focus down- cycle implicitly.
`Component`
`getLastComponent(Container aContainer)`
Returns the last Component in the traversal cycle.
`protected void`
`setComparator(Comparator<? super Component> comparator)`
Sets the Comparator which will be used to sort the Components in a focus traversal cycle.
`void`
`setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)`
Sets whether this SortingFocusTraversalPolicy transfers focus down-cycle implicitly.

### Methods declared in class InternalFrameFocusTraversalPolicy

`getInitialComponent`

### Methods declared in class FocusTraversalPolicy

`getInitialComponent`

### Methods declared in class Object

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

## Constructor Details

### 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.

Parameters:
  `comparator` - the `Comparator` to sort by

## Method Details

### getComponentAfter

public 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.

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.

If aContainer is focus traversal policy provider, the focus is always transferred down-cycle.

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)
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.

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.

If aContainer is focus traversal policy provider, the focus is always transferred down-cycle.

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(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(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(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