FocusTraversalPolicypublic abstract class FocusTraversalPolicy extends Object | 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. |
| Methods Summary |
|---|
| public abstract java.awt.Component | getComponentAfter(java.awt.Container aContainer, java.awt.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.
| | public abstract java.awt.Component | getComponentBefore(java.awt.Container aContainer, java.awt.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.
| | public abstract java.awt.Component | getDefaultComponent(java.awt.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.
| | public abstract java.awt.Component | getFirstComponent(java.awt.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.
| | public java.awt.Component | getInitialComponent(java.awt.Window window)Returns the Component that should receive the focus when a Window is
made visible for the first time. Once the Window has been made visible
by a call to 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.
if ( window == null ){
throw new IllegalArgumentException("window cannot be equal to null.");
}
Component def = getDefaultComponent(window);
if (def == null && window.isFocusableWindow()) {
def = window;
}
return def;
| | public abstract java.awt.Component | getLastComponent(java.awt.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.
|
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