Sphinx/tutorials

Model Editing Enhancements

Customizing Tree Views

The EMF Edit framework and its code generator allow creating easily editors and tree views from EMF models. However, the structure that we want displaying into tree view may be often different to the EMF model structure. The EMF Edit framework provides also mechanisms allowing customizing editors and tree views.

In the following sections, we’ll describe how to easily customize tree views in order to display customized tree view structure. There are several kings of tree view customization. For instance, we may want displaying object references as children, adding non-model elements or suppressing model objects in tree views. We’ll use an extract of the Hummingbird meta-model to illustrate these kinds of tree views customization, as shown in Figure 1:

    Figure 1: An extract of the Hummingbird meta-model 2.0.

Displaying References as Children

This section describes how displaying references as children into tree views. For example, we’ll display source port and target component (of a Connection object) as children of objects of Connection type. Realizing this kind of view customization is quite simple. The following figure illustrates this kind of tree view customization:

   Figure 2: An example displaying references as children.

We must initially override the getChildren (Object object) method of the appropriate item provider (e.g., ConnectionItemProvider. We decide creating an extended class of ConnectionItemProvider named ExtendedConnectionItemProvider) like this:

   @Override
   public Collection<? extends EStructuralFeature> getChildrenFeatures(Object object) {
       super.getChildrenFeatures(object);
       childrenFeatures.add(InstanceModel20Package.Literals.CONNECTION__SOURCE_PORT);
       childrenFeatures.add(InstanceModel20Package.Literals.CONNECTION__TARGET_COMPONENT);
       return childrenFeatures;
   }

We must also override the notifyChanged(Notification notification) method of the ExtendedConnectionItemProvider class for refreshing the view if referenced objects (e.g., source port or target component) are set or modified toward the property sheet.

   @Override
   public void notifyChanged(Notification notification) {
        updateChildren(notification);
   
        // For refreshing the view if source port and/or target component references are updated
        switch (notification.getFeatureID(Connection.class)) {
               case InstanceModel20Package.CONNECTION__SOURCE_PORT:
                    fireNotifyChanged(new ViewerNotification(notification, notification.getNotifier(), true, false));
               case InstanceModel20Package.CONNECTION__TARGET_COMPONENT:
                    fireNotifyChanged(new ViewerNotification(notification, notification.getNotifier(), true, false));
                    return;
       }
       super.notifyChanged(notification);
   }

If referenced objects are displayed as children under a transient node (i.e., a non-model object, please see section 1.1.2 for more details) then we must override in this case the notifyChanged(Notification notification) method of this transient node for refreshing node content like this:

   @Override
   public void notifyChanged(Notification notification) {
        updateTransientItemProviderChildren(notification, this);
   
        switch (notification.getFeatureID(Connection.class)) {
             case InstanceModel20Package.CONNECTION__SOURCE_PORT:
                  fireNotifyChanged(new ViewerNotification(notification, notification.getNotifier(), true, false));
             case InstanceModel20Package.CONNECTION__TARGET_COMPONENT:
                  fireNotifyChanged(new ViewerNotification(notification, notification.getNotifier(), true, false));
                  return;
        }
        super.notifyChanged(notification);
   }

Adding Transient Nodes

This section describes how to easily add transient nodes (i.e., non-model objects) between an object and its children into the tree view. We will for example introduce into the view, as shown in Figure 3, “Parameter Values” and “Outgoing Connections” transient nodes in order to separate children (of ParameterValue and Connection types) of Component model objects.