Package org.eclipse.jface.viewers

Class ViewerComparator

java.lang.Object

org.eclipse.jface.viewers.ViewerComparator

Direct Known Subclasses:

ContributionComparator, ResourceComparator, ViewerSorter, WorkbenchViewerComparator

public class ViewerComparator
extends Object

A viewer comparator is used by a StructuredViewer to reorder the elements provided by its content provider.

The default compare method compares elements using two steps. The first step uses the values returned from category. By default, all elements are in the same category. The second level uses strings obtained from the content viewer's label provider via ILabelProvider.getText(). The strings are compared using a comparator from Policy.getComparator() which by default does a case sensitive string comparison.

Subclasses may implement the isSorterProperty method; they may reimplement the category method to provide categorization; and they may override the compare methods to provide a totally different way of sorting elements.

Since:

3.2

See Also:

IStructuredContentProvider, StructuredViewer

Constructor Summary

Constructors

Constructor	Description
ViewerComparator()	Creates a new ViewerComparator, which uses the default comparator to sort strings.
ViewerComparator(Comparator<? super String> comparator)	Creates a new ViewerComparator, which uses the given comparator to sort strings.

Method Summary

Modifier and Type	Method	Description
int	category(Object element)	Returns the category of the given element.
int	compare(Viewer viewer, Object e1, Object e2)	Returns a negative, zero, or positive number depending on whether the first element is less than, equal to, or greater than the second element.
protected Comparator<? super String>	getComparator()	Returns the comparator used to sort strings.
boolean	isSorterProperty(Object element, String property)	Returns whether this viewer sorter would be affected by a change to the given property of the given element.
void	sort(Viewer viewer, Object[] elements)	Sorts the given elements in-place, modifying the given array.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ViewerComparator

public ViewerComparator()

Creates a new ViewerComparator, which uses the default comparator to sort strings.

ViewerComparator

public ViewerComparator(Comparator<? super String> comparator)

Creates a new ViewerComparator, which uses the given comparator to sort strings. The default implementation of compare(Viewer, Object, Object) expects this comparator to be able to compare the Strings provided by the viewer's label provider.

Parameters:

comparator - the comparator to use

Method Detail

getComparator

protected Comparator<? super String> getComparator()

Returns the comparator used to sort strings.

Returns:

the comparator used to sort strings

category

public int category(Object element)

Returns the category of the given element. The category is a number used to allocate elements to bins; the bins are arranged in ascending numeric order. The elements within a bin are arranged via a second level sort criterion.

The default implementation of this framework method returns 0. Subclasses may reimplement this method to provide non-trivial categorization.

Parameters:

element - the element

Returns:

the category

compare

public int compare(Viewer viewer,
                   Object e1,
                   Object e2)

Returns a negative, zero, or positive number depending on whether the first element is less than, equal to, or greater than the second element.

The default implementation of this method is based on comparing the elements' categories as computed by the category framework method. Elements within the same category are further subjected to a case insensitive compare of their label strings, either as computed by the content viewer's label provider, or their toString values in other cases. Subclasses may override.

Parameters:

viewer - the viewer

e1 - the first element

e2 - the second element

Returns:

a negative number if the first element is less than the second element; the value 0 if the first element is equal to the second element; and a positive number if the first element is greater than the second element

isSorterProperty

public boolean isSorterProperty(Object element,
                                String property)

Returns whether this viewer sorter would be affected by a change to the given property of the given element.

The default implementation of this method returns false. Subclasses may reimplement.

Parameters:

element - the element

property - the property

Returns:

true if the sorting would be affected, and false if it would be unaffected

sort

public void sort(Viewer viewer,
                 Object[] elements)

Sorts the given elements in-place, modifying the given array.

The default implementation of this method uses the Arrays.sort(Object[], Comparator) algorithm on the given array, calling compare(Viewer, Object, Object) to compare elements.

Subclasses may reimplement this method to provide a more optimized implementation.

Parameters:

viewer - the viewer

elements - the elements to sort