Class LayoutFocusTraversalPolicy

All Implemented Interfaces:
Serializable
public class LayoutFocusTraversalPolicy
extends SortingFocusTraversalPolicy
implements Serializable

A SortingFocusTraversalPolicy which sorts Components based on their size, position, and orientation. Based on their size and position, Components are roughly categorized into rows and columns. For a Container with horizontal orientation, columns run left-to-right or right-to-left, and rows run top- to-bottom. For a Container with vertical orientation, columns run top-to- bottom and rows run left-to-right or right-to-left. See ComponentOrientation for more information. All columns in a row are fully traversed before proceeding to the next row.

Since:
1.4
See Also:
ComponentOrientation, Serialized Form

Constructors

Constructor Description
LayoutFocusTraversalPolicy()

Constructs a LayoutFocusTraversalPolicy.

Methods

Modifier and Type Method Description
protected boolean accept​(Component aComponent)

Determines whether the specified Component is an acceptable choice as the new focus owner.
Component getComponentAfter​(Container aContainer, Component aComponent)

Returns the Component that should receive the focus after aComponent.
Component getComponentBefore​(Container aContainer, Component aComponent)

Returns the Component that should receive the focus before aComponent.
Component getFirstComponent​(Container aContainer)

Returns the first Component in the traversal cycle.
Component getLastComponent​(Container aContainer)

Returns the last Component in the traversal cycle.

Methods declared in class javax.swing.SortingFocusTraversalPolicy

getComparator, getDefaultComponent, getImplicitDownCycleTraversal, setComparator, setImplicitDownCycleTraversal

Methods declared in class javax.swing.InternalFrameFocusTraversalPolicy

getInitialComponent

Methods declared in class java.awt.FocusTraversalPolicy

getInitialComponent

Methods declared in class java.lang.Object

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

Constructors

LayoutFocusTraversalPolicy

public LayoutFocusTraversalPolicy()

Constructs a LayoutFocusTraversalPolicy.

Methods

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.

By default, LayoutFocusTraversalPolicy 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.

Overrides:
getComponentAfter in class SortingFocusTraversalPolicy
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.

By default, LayoutFocusTraversalPolicy 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.

Overrides:
getComponentBefore in class SortingFocusTraversalPolicy
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.

Overrides:
getFirstComponent in class SortingFocusTraversalPolicy
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.

Overrides:
getLastComponent in class SortingFocusTraversalPolicy
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

accept

protected boolean accept(Component aComponent)

Determines whether the specified Component is an acceptable choice as the new focus owner. This method performs the following sequence of operations:

  1. Checks whether aComponent is visible, displayable, enabled, and focusable. If any of these properties is false, this method returns false.
  2. If aComponent is an instance of JTable, returns true.
  3. If aComponent is an instance of JComboBox, then returns the value of aComponent.getUI().isFocusTraversable(aComponent).
  4. If aComponent is a JComponent with a JComponent.WHEN_FOCUSED InputMap that is neither null nor empty, returns true.
  5. Returns the value of DefaultFocusTraversalPolicy.accept(aComponent).

Overrides:
accept in class SortingFocusTraversalPolicy
Parameters:
aComponent - the Component whose fitness as a focus owner is to be tested
Returns:
true if aComponent is a valid choice for a focus owner; otherwise false
See Also:
Component.isVisible(), Component.isDisplayable(), Component.isEnabled(), Component.isFocusable(), ComboBoxUI.isFocusTraversable(javax.swing.JComboBox<?>), JComponent.getInputMap(int), DefaultFocusTraversalPolicy.accept(java.awt.Component)

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https://docs.oracle.com/en/java/javase/11/docs/api/java.desktop/javax/swing/LayoutFocusTraversalPolicy.html