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SortingFocusTraversalPolicy.javaAPI DocJava SE 5 API22845Fri Aug 26 14:57:58 BST 2005javax.swing

SortingFocusTraversalPolicy

public class SortingFocusTraversalPolicy extends InternalFrameFocusTraversalPolicy
A FocusTraversalPolicy that determines traversal order by sorting the Components of a focus traversal cycle based on a given Comparator. Portions of the Component hierarchy that are not visible and displayable will not be included.

By default, SortingFocusTraversalPolicy 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.

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
version
1.7, 05/05/04
see
java.util.Comparator
since
1.4

Fields Summary
private Comparator
comparator
private boolean
implicitDownCycleTraversal
private Logger
log
private Container
cachedRoot
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 sorted list before determining that they need to invoke getFirstComponent or getLastComponent, the sorted list should be reused if possible.
private List
cachedCycle
private static final SwingContainerOrderFocusTraversalPolicy
fitnessTestPolicy
Constructors Summary
protected SortingFocusTraversalPolicy()
Constructs a SortingFocusTraversalPolicy without a Comparator. Subclasses must set the Comparator using setComparator before installing this FocusTraversalPolicy on a focus cycle root or KeyboardFocusManager.


                                 
      
    
public SortingFocusTraversalPolicy(Comparator comparator)
Constructs a SortingFocusTraversalPolicy with the specified Comparator.

	this.comparator = comparator;
    
Methods Summary
protected booleanaccept(java.awt.Component aComponent)
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

	return fitnessTestPolicy.accept(aComponent);
    
private voidenumerateAndSortCycle(java.awt.Container focusCycleRoot, java.util.List cycle, java.util.Map defaults)

	List defaultRoots = null;

	if (!focusCycleRoot.isShowing()) {
	    return;
	}

	enumerateCycle(focusCycleRoot, cycle);

	boolean addDefaultComponents =
	    (defaults != null && getImplicitDownCycleTraversal());

        if (log.isLoggable(Level.FINE)) log.fine("### Will add defaults: " + addDefaultComponents);

	// Create a list of all default Components which should be added
	// to the list
	if (addDefaultComponents) {
	    defaultRoots = new ArrayList();
	    for (Iterator iter = cycle.iterator(); iter.hasNext(); ) {
		Component comp = (Component)iter.next();
		if ((comp instanceof Container) &&
		    ((Container)comp).isFocusCycleRoot())
		{
		    defaultRoots.add(comp);
		}
	    }
	    Collections.sort(defaultRoots, comparator);
	}

	// Sort the Components in the cycle
	Collections.sort(cycle, comparator);

	// Find all of the roots in the cycle and place their default
	// Components after them. Note that the roots may have been removed
	// from the list because they were unfit. In that case, insert the
	// default Components as though the roots were still in the list.
	if (addDefaultComponents) {
	    for (ListIterator defaultRootsIter = 
		     defaultRoots.listIterator(defaultRoots.size());
		 defaultRootsIter.hasPrevious(); )
	    {
		Container root = (Container)defaultRootsIter.previous();
		Component defComp =
		    root.getFocusTraversalPolicy().getDefaultComponent(root);

		if (defComp != null && defComp.isShowing()) {
		    int index = Collections.binarySearch(cycle, root,
							 comparator);
		    if (index < 0) {
			// If root is not in the list, then binarySearch
			// returns (-(insertion point) - 1). defComp follows
			// the index one less than the insertion point.
			
			index = -index - 2;
		    }
		    
		    defaults.put(new Integer(index), defComp);
		}
	    }
	}
    
private voidenumerateCycle(java.awt.Container container, java.util.List cycle)

	if (!(container.isVisible() && container.isDisplayable())) {
	    return;
	}

	cycle.add(container);

	Component[] components = container.getComponents();
	for (int i = 0; i < components.length; i++) {
	    Component comp = components[i];
	    if ((comp instanceof Container)
                && !((Container)comp).isFocusTraversalPolicyProvider()
                && !((Container)comp).isFocusCycleRoot()
                && !((comp instanceof JComponent) 
                     && ((JComponent)comp).isManagingFocus())) 
            {
		enumerateCycle((Container)comp, cycle);
	    } else {
		cycle.add(comp);
	    }
	}
    
protected java.util.ComparatorgetComparator()
Returns the Comparator which will be used to sort the Components in a focus traversal cycle.

return
the Comparator which will be used for sorting

	return comparator;
    
public java.awt.ComponentgetComponentAfter(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.

By default, SortingFocusTraversalPolicy 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

        if (log.isLoggable(Level.FINE)) log.fine("### Searching in " + aContainer.getName() + " for component after " + aComponent.getName());

        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");
        }

        // See if the component is inside of policy provider
        Container ftp = getTopmostProvider(aContainer, aComponent);
        if (ftp != null) {
            if (log.isLoggable(Level.FINE)) log.fine("### Asking FTP " + ftp.getName() + " for component after " + aComponent.getName());
            // FTP knows how to find component after the given. We don't.
            FocusTraversalPolicy policy = ftp.getFocusTraversalPolicy();
            Component retval = policy.getComponentAfter(ftp, aComponent);
            if (retval == policy.getFirstComponent(ftp)) {
                retval = null;
            }
            
            if (retval != null) {
                if (log.isLoggable(Level.FINE)) log.fine("### FTP returned " + retval.getName());
                return retval;
        }
            aComponent = ftp;
        }

	List cycle = new ArrayList();
	Map defaults = new HashMap();
        enumerateAndSortCycle(aContainer, cycle, defaults);

	int index;
	try {
	    index = Collections.binarySearch(cycle, aComponent, comparator);
	} catch (ClassCastException e) {
            if (log.isLoggable(Level.FINE)) log.fine("### Didn't find component " + aComponent.getName() + " in a cycle " + aContainer.getName());
            return getFirstComponent(aContainer);
	}

	if (index < 0) {
	    // If we're not in the cycle, then binarySearch returns
	    // (-(insertion point) - 1). The next element is our insertion
	    // point.

	    index = -index - 2;
	}

	Component defComp = (Component)defaults.get(new Integer(index));
	if (defComp != null) {
	    return defComp;
	}

        do {
	index++;

	if (index >= cycle.size()) {
                if (aContainer.isFocusCycleRoot()) {
                    this.cachedRoot = aContainer;
	    this.cachedCycle = cycle;

                    Component retval = getFirstComponent(aContainer);

	    this.cachedRoot = null;
	    this.cachedCycle = null;

	    return retval;
	} else {
                    return null;
                }
            } else {
                Component comp = (Component)cycle.get(index);
                if (accept(comp)) {
                    return comp;
                } else if (comp instanceof Container && ((Container)comp).isFocusTraversalPolicyProvider()) {
                    return ((Container)comp).getFocusTraversalPolicy().getDefaultComponent((Container)comp);
                }
	}
        } while (true);
    
public java.awt.ComponentgetComponentBefore(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.

By default, SortingFocusTraversalPolicy 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

        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");
        }

        // See if the component is inside of policy provider
        Container ftp = getTopmostProvider(aContainer, aComponent);
        if (ftp != null) {
            if (log.isLoggable(Level.FINE)) log.fine("### Asking FTP " + ftp.getName() + " for component after " + aComponent.getName());
            // FTP knows how to find component after the given. We don't.
            FocusTraversalPolicy policy = ftp.getFocusTraversalPolicy();
            Component retval = policy.getComponentBefore(ftp, aComponent);
            if (retval == policy.getLastComponent(ftp)) {
                retval = null;
            }
            if (retval != null) {
                if (log.isLoggable(Level.FINE)) log.fine("### FTP returned " + retval.getName());
                return retval;
        }
            aComponent = ftp;
        }


	List cycle = new ArrayList();
	Map defaults = new HashMap();
        enumerateAndSortCycle(aContainer, cycle, defaults);

        if (log.isLoggable(Level.FINE)) log.fine("### Cycle is " + cycle + ", component is " + aComponent);

	int index;
	try {
	    index = Collections.binarySearch(cycle, aComponent, comparator);
	} catch (ClassCastException e) {
            return getLastComponent(aContainer);
	}

	if (index < 0) {
	    // If we're not in the cycle, then binarySearch returns
	    // (-(insertion point) - 1). The previous element is our insertion
	    // point - 1.
	    
            index = -index - 2;
	} else {
            index--;
        }

        if (log.isLoggable(Level.FINE)) log.fine("### Index is " + index);

        if (index >= 0) {
            Component defComp = (Component)defaults.get(new Integer(index));            
            if (defComp != null && cycle.get(index) != aContainer) {
                if (log.isLoggable(Level.FINE)) log.fine("### Returning default " + defComp.getName() + " at " + index);
                return defComp;
            }
        }

        do {
	if (index < 0) {
                this.cachedRoot = aContainer;
	    this.cachedCycle = cycle;

                Component retval = getLastComponent(aContainer);

	    this.cachedRoot = null;
	    this.cachedCycle = null;

	    return retval;
	} else {
                Component comp = (Component)cycle.get(index);
                if (accept(comp)) {
                    return comp;
                } else if (comp instanceof Container && ((Container)comp).isFocusTraversalPolicyProvider()) {
                    return ((Container)comp).getFocusTraversalPolicy().getLastComponent((Container)comp);
	    }
	}
            index--;
        } while (true);
    
public java.awt.ComponentgetDefaultComponent(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. The default implementation of this method returns the same Component as getFirstComponent.

param
aContainer a focus cycle root of aComponent or a 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

        return getFirstComponent(aContainer);
    
public java.awt.ComponentgetFirstComponent(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.

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

	List cycle;

        if (log.isLoggable(Level.FINE)) log.fine("### Getting first component in " + aContainer.getName());
        if (aContainer == null) {
            throw new IllegalArgumentException("aContainer cannot be null");
	}

        if (this.cachedRoot == aContainer) {
	    cycle = this.cachedCycle;
	} else {
	    cycle = new ArrayList();
            enumerateAndSortCycle(aContainer, cycle, null);
	}

	int size = cycle.size();
	if (size == 0) {
	    return null;
	}

        for (int i= 0; i < cycle.size(); i++) {
            Component comp = (Component)cycle.get(i);
            if (accept(comp)) {
                return comp;
            } else if (comp instanceof Container && !(comp == aContainer) && ((Container)comp).isFocusTraversalPolicyProvider()) {
                return ((Container)comp).getFocusTraversalPolicy().getDefaultComponent((Container)comp);
            }            
        }
        return null;
    
public booleangetImplicitDownCycleTraversal()
Returns whether this SortingFocusTraversalPolicy transfers focus down- cycle implicitly. If true, during normal 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 SortingFocusTraversalPolicy transfers focus down- cycle implicitly
see
#setImplicitDownCycleTraversal
see
#getFirstComponent

	return implicitDownCycleTraversal;
    
public java.awt.ComponentgetLastComponent(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.

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

	List cycle;
        if (log.isLoggable(Level.FINE)) log.fine("### Getting last component in " + aContainer.getName());

        if (aContainer == null) {
            throw new IllegalArgumentException("aContainer cannot be null");
	}

        if (this.cachedRoot == aContainer) {
	    cycle = this.cachedCycle;
	} else {
	    cycle = new ArrayList();
            enumerateAndSortCycle(aContainer, cycle, null);
	}

	int size = cycle.size();
	if (size == 0) {
            if (log.isLoggable(Level.FINE)) log.fine("### Cycle is empty");
	    return null;
	}
        if (log.isLoggable(Level.FINE)) log.fine("### Cycle is " + cycle);

        for (int i= cycle.size()-1; i >= 0; i--) {
            Component comp = (Component)cycle.get(i);
            if (accept(comp)) {
                return comp;
            } else if (comp instanceof Container && !(comp == aContainer) && ((Container)comp).isFocusTraversalPolicyProvider()) {
                return ((Container)comp).getFocusTraversalPolicy().getLastComponent((Container)comp);
            }            
        }
        return null;
    
java.awt.ContainergetTopmostProvider(java.awt.Container focusCycleRoot, java.awt.Component aComponent)

        Container aCont = aComponent.getParent();
        Container ftp = null;
        while (aCont  != focusCycleRoot && aCont != null) {
            if (aCont.isFocusTraversalPolicyProvider()) {
                ftp = aCont;
            }
            aCont = aCont.getParent();
        }
        if (aCont == null) {
            return null;
        }
        return ftp;
    
protected voidsetComparator(java.util.Comparator comparator)
Sets the Comparator which will be used to sort the Components in a focus traversal cycle.

param
comparator the Comparator which will be used for sorting

	this.comparator = comparator;
    
public voidsetImplicitDownCycleTraversal(boolean implicitDownCycleTraversal)
Sets whether this SortingFocusTraversalPolicy transfers focus down-cycle implicitly. If true, during normal 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 SortingFocusTraversalPolicy transfers focus down-cycle implicitly
see
#getImplicitDownCycleTraversal
see
#getFirstComponent

	this.implicitDownCycleTraversal = implicitDownCycleTraversal;