Container.getComponents(). Portions of the hierarchy that are
* not visible and displayable will not be searched.
*
* By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus
* down-cycle. That is, during normal forward 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.
*
* @author David Mendenhall
*
* @see Container#getComponents
* @since 1.4
*/
public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy
implements java.io.Serializable
{
private static final Logger log = Logger.getLogger("java.awt.ContainerOrderFocusTraversalPolicy");
final private int FORWARD_TRAVERSAL = 0;
final private int BACKWARD_TRAVERSAL = 1;
/*
* JDK 1.4 serialVersionUID
*/
private static final long serialVersionUID = 486933713763926351L;
private boolean implicitDownCycleTraversal = true;
/**
* Used by getComponentAfter and getComponentBefore for efficiency. In
* order to maintain compliance with the specification of
* FocusTraversalPolicy, if traversal wraps, we should invoke
* getFirstComponent or getLastComponent. These methods may be overriden in
* subclasses to behave in a non-generic way. However, in the generic case,
* these methods will simply return the first or last Components of the
* sorted list, respectively. Since getComponentAfter and
* getComponentBefore have already built the list before determining
* that they need to invoke getFirstComponent or getLastComponent, the
* list should be reused if possible.
*/
transient private Container cachedRoot;
transient private List cachedCycle;
/*
* We suppose to use getFocusTraversalCycle & getComponentIndex methods in order
* to divide the policy into two parts:
* 1) Making the focus traversal cycle.
* 2) Traversing the cycle.
* The 1st point assumes producing a list of components representing the focus
* traversal cycle. The two methods mentioned above should implement this logic.
* The 2nd point assumes implementing the common concepts of operating on the
* cycle: traversing back and forth, retrieving the initial/default/first/last
* component. These concepts are described in the AWT Focus Spec and they are
* applied to the FocusTraversalPolicy in general.
* Thus, a descendant of this policy may wish to not reimplement the logic of
* the 2nd point but just override the implementation of the 1st one.
* A striking example of such a descendant is the javax.swing.SortingFocusTraversalPolicy.
*/
/*protected*/ private List
* By default, ContainerOrderFocusTraversalPolicy implicitly transfers
* focus down-cycle. That is, during normal forward 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
* If aContainer is focus
* traversal policy provider, the focus is always transferred down-cycle.
*
* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider
* @param aComponent a (possibly indirect) child of aContainer, or
* aContainer itself
* @return 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 focus traversal policy provider, or if either aContainer or
* aComponent is null
*/
public Component getComponentAfter(Container aContainer, Component aComponent) {
if (log.isLoggable(Level.FINE)) log.fine("### Searching in " + aContainer + " for component after " + aComponent);
if (aContainer == null || aComponent == null) {
throw new IllegalArgumentException("aContainer and aComponent cannot be null");
}
if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {
throw new IllegalArgumentException("aContainer should be focus cycle root or focus traversal policy provider");
} else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {
throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");
}
synchronized(aContainer.getTreeLock()) {
if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
return null;
}
// Before all the ckecks below we first see if it's an FTP provider or a focus cycle root.
// If it's the case just go down cycle (if it's set to "implicit").
Component comp = getComponentDownCycle(aComponent, FORWARD_TRAVERSAL);
if (comp != null) {
return comp;
}
// See if the component is inside of policy provider.
Container provider = getTopmostProvider(aContainer, aComponent);
if (provider != null) {
if (log.isLoggable(Level.FINE)) {
log.fine("### Asking FTP " + provider + " for component after " + aComponent);
}
// FTP knows how to find component after the given. We don't.
FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();
Component afterComp = policy.getComponentAfter(provider, aComponent);
// Null result means that we overstepped the limit of the FTP's cycle.
// In that case we must quit the cycle, otherwise return the component found.
if (afterComp != null) {
if (log.isLoggable(Level.FINE)) log.fine("### FTP returned " + afterComp);
return afterComp;
}
aComponent = provider;
}
ListsetImplicitDownCycleTraversal method.
* getFirstComponent.
*
* @param aContainer the focus cycle root or focus traversal policy provider whose default
* Component is to be returned
* @return the default Component in the traversal cycle of aContainer,
* or null if no suitable Component can be found
* @see #getFirstComponent
* @throws IllegalArgumentException if aContainer is null
*/
public Component getDefaultComponent(Container aContainer) {
return getFirstComponent(aContainer);
}
/**
* Sets whether this ContainerOrderFocusTraversalPolicy transfers focus
* down-cycle implicitly. If true, during normal forward 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.
*
* @param implicitDownCycleTraversal whether this
* ContainerOrderFocusTraversalPolicy transfers focus down-cycle
* implicitly
* @see #getImplicitDownCycleTraversal
* @see #getFirstComponent
*/
public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal) {
this.implicitDownCycleTraversal = implicitDownCycleTraversal;
}
/**
* Returns whether this ContainerOrderFocusTraversalPolicy transfers focus
* down-cycle implicitly. If true, during normal forward 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.
*
* @return whether this ContainerOrderFocusTraversalPolicy transfers focus
* down-cycle implicitly
* @see #setImplicitDownCycleTraversal
* @see #getFirstComponent
*/
public boolean getImplicitDownCycleTraversal() {
return implicitDownCycleTraversal;
}
/**
* 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.
*
* @param aComponent the Component whose fitness as a focus owner is to
* be tested
* @return true if aComponent is visible, displayable,
* enabled, and focusable; false otherwise
*/
protected boolean accept(Component aComponent) {
if (!aComponent.canBeFocusOwner()) {
return false;
}
// Verify that the Component is recursively enabled. Disabling a
// heavyweight Container disables its children, whereas disabling
// a lightweight Container does not.
if (!(aComponent instanceof Window)) {
for (Container enableTest = aComponent.getParent();
enableTest != null;
enableTest = enableTest.getParent())
{
if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
return false;
}
if (enableTest instanceof Window) {
break;
}
}
}
return true;
}
}