E4 RCP How to set selection of ToolBarItem that contains Radio Buttons - drop-down-menu

Question

In Eclipse E4 (Luna), using the application model to create parts, handlers, commands, handled menu items etc, (these are not created programatically). I have a toolbar. This contains a sub-Menu item called "Filter" that contains another sub-menu of two filters. The two filters are two Handled Menu Items which are set up as "Radio" Buttons.
When I select the appropriate in the UI of my running app from the selection, the Radio button switches just fine to the selected Item. However I would like this selection to update (deselecting one Radio button and selecting the appropriate radio button of the handled menu item) when my ViewPart changes through other UI selection. Currently my ViewPart updates, but the Radio buttons are on the same previous selection through the UI.
Is there a way in which I get access both Handled Menu Item's IDs and set the selection (one to false, the other to true) when the viewer is updated.
Image of design is attached below:
Hierarchy of the application model is as follows:
Thanks in advance,
Marv

Answer 1

You can use the model service to find menu items. Use something like:
#Inject
EModelService modelService;
#Inject
MApplication app;
List<MMenuItem> items = modelService.findElements(app, "menu item id", MMenuItem.class, Collections.emptyList(), EModelService.IN_MAIN_MENU);
Once you have the MMenuItem you can call the setSelected(boolean) method to change the selection.
To find a menu item which is in a Part menu use:
modelService.findElements(app, "menu item id", MMenuItem.class, Collections.emptyList(), EModelService.IN_PART);
(IN_PART argument instead of IN_MAIN_MENU).
You could also specify the MPart rather than the Application as the first argument to findElements which may speed up the search.
For menus as a child of a Tool Bar Item it appears that the model services cannot find these directly. However you can find the Tool Bar Item and look at the menu yourself:
List<MToolItem> items = modelService.findElements(app, "tool bar item id", MToolItem.class, Collections.emptyList(), EModelService.IN_PART);
MToolItem item = items.get(0);
MMenu menu = item.getMenu();
List<MMenuElement> children = menu.getChildren();
... search menu elements

Answer 2

I solved this by starting with MPart PartID and drilling down to the HandledMenuItems on which I wanted to set the Radio Button selections, then setting the selection property for each individual HandledMenuItem.
This can probably be refactored to be more concise, but I've left the code with each step to have the solution easier to read.
BTW, in every instance / combination of the EModelService methods, the list returned a size of 0. So I'm not certain if that will work for what I'm trying to achieve. The following does work, although I'm not certain it is the most efficient means.
I hope this helps others.
// Get view part
MPart viewPart = _partService.findPart("part_id");
// get list of all menu items from the Part
List<MMenu> viewPartMenu = viewPart.getMenus();
// Get list of ViewMenus from viewPartMenu there is only one View Menu so it will be index 0
MMenu viewMenu = viewPartMenu .get(0);
// Get list of MMenuElements from the viewMenu - the children in the view menu
List<MMenuElement> viewMenuElements = viewMenu.getChildren();
// This gets me to the 2 HandledMenuItems
// Upper Most HandledMenuItem Radio Button is at viewMenuElements index 0. This is cast to MHandledMenuItem
MHandledMenuItem upperHandledMenuItem = (MHandledMenuItem) viewMenuElements.get(0);
// Set Selection
upperHandledMenuItem.setSelected(false);
// Lower Most HandledMenuItem Radio Button is at viewMenuElements index 1. This is cast to MHandledMenuItem
MHandledMenuItem lowerHandledMenuItem = (MHandledMenuItem) viewMenuElements.get(1);
// Set selection
lowerHandledMenuItem.setSelected(true);