Qt Model/View selections

An example application plug-in with a minimal selection service based on Qt selection models.

In this example the selection service is used to connect the selection of the radio buttons from one view with the selection of the list of the other view. The SelectionView holds a QListWidget that provides the user selection (qt selection provider) for the selection listener (ListenerView). The radio buttons of the listener view are changed according to the selection in the QListWidget. Vice versa the radio buttons (the selection listener) does not provide any selection events. If the user changes the radio button state the QListWidget is not altered.

For additional informations on the selection service concept see http://www.mitk.org/wiki/Article_Using_the_Selection_Service

The berry::QtSelectionProvider class implements the interface berry::ISelectionProvider. Due to the model/view concept in Qt, the workbench provides the berry::QtSelectionProvider class for Qt viewers which must be provided with a QItemSelectionModel.

In the SelectionView.h we declare a pointer that holds the selection provider...

  berry::QtSelectionProvider::Pointer m_SelectionProvider;

...and in the SelectionView.cpp we set the selection model to the model of the QListWidget (m_SelectionList)

  // create new qt selection provider
  m_SelectionProvider = new berry::QtSelectionProvider();
  // set the item selection model to the model of the QListWidget
  m_SelectionProvider->SetItemSelectionModel(m_Controls.m_SelectionList->selectionModel());
  // register selection provider
  GetSite()->SetSelectionProvider(m_SelectionProvider);

Now that the QListWidget of the SelectionView sends out selection events we need a listener implementation. In the ListenerView.h we need to include the ISelectionListener which is a simple class with just one method.

The method that implements the selection listener functionality of ISelectionListener and the pointer that holds the selection listener is declared...

  void SelectionChanged(const berry::IWorkbenchPart::Pointer &sourcepart,
                        const berry::ISelection::ConstPointer &selection);

  QScopedPointer<berry::ISelectionListener> m_SelectionListener;

...and implemented in the cpp-file:

void ListenerView::SelectionChanged(const berry::IWorkbenchPart::Pointer &sourcepart,
                                    const berry::ISelection::ConstPointer &selection)
{
  // check for null selection
  if (selection.IsNull())
  {
    return;
  }
  // exclude own selection events and check whether this kind of selection can be handled
  if (sourcepart != this && selection.Cast<const berry::IStructuredSelection>())
  {
    berry::IStructuredSelection::ConstPointer currentSelection = selection.Cast<const berry::IStructuredSelection>();
    // iterate over the selections (for the BlueBerry example this is always 1
    for (berry::IStructuredSelection::iterator itr = currentSelection->Begin(); itr != currentSelection->End(); ++itr)
    {
      if (berry::QModelIndexObject::Pointer object = itr->Cast<berry::QModelIndexObject>())
      {
        // get name of selected ListWidgetElement
        QVariant text = object->GetQModelIndex().data();
        // pass name of element to method for radio button state checking
        ToggleRadioMethod(text.toString());
      }
    }
  }
}

Now the name of the selected list element is passed to a method that toggles the radio buttons of the ListenerView accordingly.

View complete source files:

• SelectionView.cpp
• SelectionView.h
• ListenerView.cpp
• ListenerView.h

[Selection Service] [Next: MITK DataNode Selections] [BlueBerry Examples]