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How to do empty selection (IStructuredSelection.isEmpty() == true)? [message #901399]

Sat, 11 August 2012 15:01

Eclipse User

Hi all,
I'm just wondering how to do "empty" selection as a user of e.g. TreeViewer.

Because when selection changed event is triggered it is because
something has been selected so I don't understand how this "something"
can be empty.

treeViewer.addSelectionChangedListener(new ISelectionChangedListener() {
public void selectionChanged(SelectionChangedEvent event) {

// When this selection will be empty??
if(event.getSelection().isEmpty()) {
return;
}
...
}
});

Thanks
Libor

Re: How to do empty selection (IStructuredSelection.isEmpty() == true)? [message #901408 is a reply to message #901399]

Sat, 11 August 2012 18:34

Eclipse User

Hi Libor,

your Tree probably has the style SWT.SINGLE. If you set it's style to SWT.MULTI, it is possible to clear the selection (i.e. through Ctrl+Click on the last selected element).

Greetings
Christoph

Re: How to do empty selection (IStructuredSelection.isEmpty() == true)? [message #901481 is a reply to message #901408]

Sun, 12 August 2012 23:00

Eclipse User

step 1:you select a tree item
step 2:program deleted the selected tree item
step 3: a selection changed event with empty selection is fired

Re: How to do empty selection (IStructuredSelection.isEmpty() == true)? [message #901537 is a reply to message #901481]

Mon, 13 August 2012 05:46

Eclipse User

If you request a selection from a non selected viewer you will get an EMPTY selection (not null). On the other hand the selection of a viewer is/can be cleared by setting an EMPTY selection. That's why selection.isEmpty() actually makes sense. See for example:

org.eclipse.jface.viewers.StructuredSelection.EMPTY

Regards
Thorsten

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