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Java™ Platform Standard Ed. 6 |
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java.lang.Object java.awt.FocusTraversalPolicy
public abstract class FocusTraversalPolicy
A FocusTraversalPolicy defines the order in which Components with a particular focus cycle root are traversed. Instances can apply the policy to arbitrary focus cycle roots, allowing themselves to be shared across Containers. They do not need to be reinitialized when the focus cycle roots of a Component hierarchy change.
The core responsibility of a FocusTraversalPolicy is to provide algorithms determining the next and previous Components to focus when traversing forward or backward in a UI. Each FocusTraversalPolicy must also provide algorithms for determining the first, last, and default Components in a traversal cycle. First and last Components are used when normal forward and backward traversal, respectively, wraps. The default Component is the first to receive focus when traversing down into a new focus traversal cycle. A FocusTraversalPolicy can optionally provide an algorithm for determining a Window's initial Component. The initial Component is the first to receive focus when a Window is first made visible.
FocusTraversalPolicy 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.
Please see How to Use the Focus Subsystem, a section in The Java Tutorial, and the Focus Specification for more information.
Container.setFocusTraversalPolicy(java.awt.FocusTraversalPolicy)
,
Container.getFocusTraversalPolicy()
,
Container.setFocusCycleRoot(boolean)
,
Container.isFocusCycleRoot(java.awt.Container)
,
Container.setFocusTraversalPolicyProvider(boolean)
,
Container.isFocusTraversalPolicyProvider()
,
KeyboardFocusManager.setDefaultFocusTraversalPolicy(java.awt.FocusTraversalPolicy)
,
KeyboardFocusManager.getDefaultFocusTraversalPolicy()
Constructor Summary | |
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FocusTraversalPolicy()
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Method Summary | |
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abstract Component |
getComponentAfter(Container aContainer,
Component aComponent)
Returns the Component that should receive the focus after aComponent. |
abstract Component |
getComponentBefore(Container aContainer,
Component aComponent)
Returns the Component that should receive the focus before aComponent. |
abstract Component |
getDefaultComponent(Container aContainer)
Returns the default Component to focus. |
abstract Component |
getFirstComponent(Container aContainer)
Returns the first Component in the traversal cycle. |
Component |
getInitialComponent(Window window)
Returns the Component that should receive the focus when a Window is made visible for the first time. |
abstract Component |
getLastComponent(Container aContainer)
Returns the last Component in the traversal cycle. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public FocusTraversalPolicy()
Method Detail |
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public abstract Component getComponentAfter(Container aContainer, Component aComponent)
aContainer
- a focus cycle root of aComponent or focus traversal
policy provideraComponent
- a (possibly indirect) child of aContainer, or
aContainer itself
IllegalArgumentException
- if aContainer is not a focus cycle
root of aComponent or a focus traversal policy provider, or if
either aContainer or aComponent is nullpublic abstract Component getComponentBefore(Container aContainer, Component aComponent)
aContainer
- a focus cycle root of aComponent or focus traversal
policy provideraComponent
- a (possibly indirect) child of aContainer, or
aContainer itself
IllegalArgumentException
- if aContainer is not a focus cycle
root of aComponent or a focus traversal policy provider, or if
either aContainer or aComponent is nullpublic abstract Component getFirstComponent(Container aContainer)
aContainer
- the focus cycle root or focus traversal policy provider
whose first Component is to be returned
IllegalArgumentException
- if aContainer is nullpublic abstract Component getLastComponent(Container aContainer)
aContainer
- the focus cycle root or focus traversal policy
provider whose last Component is to be returned
IllegalArgumentException
- if aContainer is nullpublic abstract Component getDefaultComponent(Container aContainer)
aContainer
- the focus cycle root or focus traversal policy
provider whose default Component is to be returned
IllegalArgumentException
- if aContainer is nullpublic Component getInitialComponent(Window window)
show()
or setVisible(true)
, the
initial Component will not be used again. Instead, if the Window loses
and subsequently regains focus, or is made invisible or undisplayable
and subsequently made visible and displayable, the Window's most
recently focused Component will become the focus owner. The default
implementation of this method returns the default Component.
window
- the Window whose initial Component is to be returned
IllegalArgumentException
- if window is nullgetDefaultComponent(java.awt.Container)
,
Window.getMostRecentFocusOwner()
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Java™ Platform Standard Ed. 6 |
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