Time for action – sorting items in a viewer

The TreeViewer already shows data in a sorted list, but this is not a view-imposed sort. Because the data is stored in a TreeMap, the sort ordering is created by the TreeMap itself, which in turn is sorting on the value of the toString method. To use a different ordering (say, based on the timezone offset) the choices are either to modify the TreeMap to add a Comparator and sort the data at creation time, or add a sorter to the TreeViewer. The first choice is applicable if the data is only used by a single view, or if the data is coming from a large external data store which can perform the sorting more efficiently (such as a relational database). For smaller data sets, the sorting can be done in the viewer itself.

1. JFace structured viewers allow view-specific sorting with the ViewerComparator. Create a new subclass called TimeZoneViewerComparator in the com.packtpub.e4.clock.ui.internal package, and implement the compare method as follows:

   public...