fFilterDropDownAction.setEnabled(true);
	protected void setTreeViewerInput() {		if (fTreeViewer == null)			return;		PreviewNode input= null;		if (fTreeViewerInputChange != null) {			input= AbstractChangeNode.createNode(null, fFilter, fTreeViewerInputChange);		}		if (input instanceof CompositeChangeNode) {			final CompositeChangeNode node= (CompositeChangeNode) input;			final PreviewNode[] nodes= node.getChildren();			if (nodes == null || nodes.length == 0) {				fTreeViewerPane.setText(RefactoringUIMessages.RefactoringHistoryPreviewPage_no_changes);				fNextAction.setEnabled(false);				fPreviousAction.setEnabled(false);				fTreeViewer.setInput(null);				return;			}		}		fTreeViewerPane.setText(RefactoringUIMessages.PreviewWizardPage_changes);		fNextAction.setEnabled(true);		fPreviousAction.setEnabled(true);		fTreeViewer.setInput(input);	}