Display UIMenuController in UIBarButton Click - xamarin.ios

Question

I am trying to display a UIMenuController in a Toolbar button. I have the code below but I am unsure as to what should be in the "SetTargetRect" method.
What should I put in the SetTargetRect method to display the Menu?
Is there anything else that is missing from this code?
ToolbarItems = new UIBarButtonItem[] {
new UIBarButtonItem ("Sort", UIBarButtonItemStyle.Bordered, (sender, e) => {
var menu = UIMenuController.SharedMenuController;
menu.MenuItems = new UIMenuItem[] {
new UIMenuItem ("Current", new Selector ("SortRaceEntrants")),
new UIMenuItem ("Movers", new Selector ("SortRaceEntrants")),
new UIMenuItem ("Opening", new Selector ("SortRaceEntrants")),
new UIMenuItem ("Number", new Selector ("SortRaceEntrants"))
};
//menu.SetTargetRect ();
menu.SetMenuVisible (true, true);
}),
};

Answer 1

UIBarButtonItem inherits from UIBarItem and NSObject, so finding a frame for them is not easy if not impossible. UINavigationBar inherits from UIView and thus is a view (go figure) and has a frame, etc.
What I do is point to a rect inside that view where the UIBarButtonItem should be.
For example:
[myMenu setTargetRect:CGRectMake(10, 10, 20, 25)
inView:self.navigationController.navigationBar];
This will make the UIMenuController 'point' at the leftBarButtonItem.
The same technique can be used for the toolbar.
In your case something like:
[menu setTargetRect:CGRectMake(0,0,40,40)
inView:self.navigationController.toolBar];
would point to the center of the toolBar and thus the center button in the toolBar

Answer 2

According to the API docs, the target rect defines the area that you want to display the menu relative to - iOS will either show the menu above or below the area defined by TargetRect.
When you make this menu visible, UIMenuController positions it
relative to a target rectangle on the screen; this rectangle usually
defines a selection. The menu appears above the target rectangle or,
if there is not enough space for it, below it. The menu’s pointer is
placed at the center of the top or bottom of the target rectangle, as
appropriate. Be sure to set the tracking rectangle before you make the
menu visible. You are also responsible for detecting, tracking, and
displaying selections.
and
This target rectangle (targetRect) is usually the bounding rectangle
of a selection. UIMenuController positions the editing menu above this
rectangle; if there is not enough space for the menu there, it
positions it below the rectangle. The menu’s pointer is placed at the
center of the top or bottom of the target rectangle as appropriate.
Note that if you make the width or height of the target rectangle
zero, UIMenuController treats the target area as a line or point for
positioning (for example, an insertion caret or a single point).
Once it is set, the target rectangle does not track the view; if the
view moves (such as would happen in a scroll view), you must update
the target rectangle accordingly.