ComponentOrientation for more information. All columns in a
* row are fully traversed before proceeding to the next row.
*
* @author David Mendenhall
*
* @see java.awt.ComponentOrientation
* @since 1.4
*/
@SuppressWarnings("serial") // Parts of superclass are not serializable across versions
public class LayoutFocusTraversalPolicy extends SortingFocusTraversalPolicy
implements Serializable
{
// Delegate most of our fitness test to Default so that we only have to
// code the algorithm once.
private static final SwingDefaultFocusTraversalPolicy fitnessTestPolicy =
new SwingDefaultFocusTraversalPolicy();
/**
* Constructs a LayoutFocusTraversalPolicy.
*/
public LayoutFocusTraversalPolicy() {
super(new LayoutComparator());
}
/**
* Constructs a LayoutFocusTraversalPolicy with the passed in
* Comparator.
*/
LayoutFocusTraversalPolicy(Comparator c) {
super(c);
}
/**
* 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. * * @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 a focus traversal policy provider, or if either aContainer or * aComponent is null */ public Component getComponentAfter(Container aContainer, Component aComponent) { if (aContainer == null || aComponent == null) { throw new IllegalArgumentException("aContainer and aComponent cannot be null"); } Comparator comparator = getComparator(); if (comparator instanceof LayoutComparator) { ((LayoutComparator)comparator). setComponentOrientation(aContainer. getComponentOrientation()); } return super.getComponentAfter(aContainer, 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.
*
* @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 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
*/
public Component getComponentBefore(Container aContainer,
Component aComponent) {
if (aContainer == null || aComponent == null) {
throw new IllegalArgumentException("aContainer and aComponent cannot be null");
}
Comparator comparator = getComparator();
if (comparator instanceof LayoutComparator) {
((LayoutComparator)comparator).
setComponentOrientation(aContainer.
getComponentOrientation());
}
return super.getComponentBefore(aContainer, aComponent);
}
/**
* 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.
*
* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose
* first Component is to be returned
* @return the first Component in the traversal cycle of aContainer,
* or null if no suitable Component can be found
* @throws IllegalArgumentException if aContainer is null
*/
public Component getFirstComponent(Container aContainer) {
if (aContainer == null) {
throw new IllegalArgumentException("aContainer cannot be null");
}
Comparator comparator = getComparator();
if (comparator instanceof LayoutComparator) {
((LayoutComparator)comparator).
setComponentOrientation(aContainer.
getComponentOrientation());
}
return super.getFirstComponent(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.
*
* @param aContainer a focus cycle root of aComponent or a focus traversal policy provider whose
* last Component is to be returned
* @return the last Component in the traversal cycle of aContainer,
* or null if no suitable Component can be found
* @throws IllegalArgumentException if aContainer is null
*/
public Component getLastComponent(Container aContainer) {
if (aContainer == null) {
throw new IllegalArgumentException("aContainer cannot be null");
}
Comparator comparator = getComparator();
if (comparator instanceof LayoutComparator) {
((LayoutComparator)comparator).
setComponentOrientation(aContainer.
getComponentOrientation());
}
return super.getLastComponent(aContainer);
}
/**
* Determines whether the specified Component
* is an acceptable choice as the new focus owner.
* This method performs the following sequence of operations:
*
aComponent is visible, displayable,
* enabled, and focusable. If any of these properties is
* false, this method returns false.
* aComponent is an instance of JTable,
* returns true.
* aComponent is an instance of JComboBox,
* then returns the value of
* aComponent.getUI().isFocusTraversable(aComponent).
* aComponent is a JComponent
* with a JComponent.WHEN_FOCUSED
* InputMap that is neither null
* nor empty, returns true.
* DefaultFocusTraversalPolicy.accept(aComponent).
* Component whose fitness
* as a focus owner is to be tested
* @see java.awt.Component#isVisible
* @see java.awt.Component#isDisplayable
* @see java.awt.Component#isEnabled
* @see java.awt.Component#isFocusable
* @see javax.swing.plaf.ComboBoxUI#isFocusTraversable
* @see javax.swing.JComponent#getInputMap
* @see java.awt.DefaultFocusTraversalPolicy#accept
* @return true if aComponent is a valid choice
* for a focus owner;
* otherwise false
*/
protected boolean accept(Component aComponent) {
if (!super.accept(aComponent)) {
return false;
} else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JTable")) {
// JTable only has ancestor focus bindings, we thus force it
// to be focusable by returning true here.
return true;
} else if (SunToolkit.isInstanceOf(aComponent, "javax.swing.JComboBox")) {
JComboBox box = (JComboBox)aComponent;
return box.getUI().isFocusTraversable(box);
} else if (aComponent instanceof JComponent) {
JComponent jComponent = (JComponent)aComponent;
InputMap inputMap = jComponent.getInputMap(JComponent.WHEN_FOCUSED,
false);
while (inputMap != null && inputMap.size() == 0) {
inputMap = inputMap.getParent();
}
if (inputMap != null) {
return true;
}
// Delegate to the fitnessTestPolicy, this will test for the
// case where the developer has overriden isFocusTraversable to
// return true.
}
return fitnessTestPolicy.accept(aComponent);
}
private void writeObject(ObjectOutputStream out) throws IOException {
out.writeObject(getComparator());
out.writeBoolean(getImplicitDownCycleTraversal());
}
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException
{
setComparator((Comparator)in.readObject());
setImplicitDownCycleTraversal(in.readBoolean());
}
}
// Create our own subclass and change accept to public so that we can call
// accept.
@SuppressWarnings("serial") // JDK-implementation class
class SwingDefaultFocusTraversalPolicy
extends java.awt.DefaultFocusTraversalPolicy
{
public boolean accept(Component aComponent) {
return super.accept(aComponent);
}
}