Class 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.

    See Also:
    IStructuredContentProvider, StructuredViewer
    • 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.
        comparator - the comparator to use
    • Method Detail

      • getComparator

        protected Comparator<? super String> getComparator()
        Returns the comparator used to sort strings.
        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.

        element - the element
        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.

        viewer - the viewer
        e1 - the first element
        e2 - the second element
        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.

        element - the element
        property - the property
        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.

        viewer - the viewer
        elements - the elements to sort