IOS: Creating full screen 'overlay' UIView (Monotouch) - ios

Question

I have a view within a navigationcontroller, and would like to create a 'full (application) screen' overlay that says a couple of things about what the user should do. I've seen this done with a bit of transparency on other apps and it works well. I'm trying the below, but the content ends up beneath my navcontroller headers. Investigations talk about converting the rectangle to a 'window level' location etc, but still it is underneath.
Any alternatives to my feeble attempt below? Or a link to a sample would be great too.
Thanks!
HelpOverlayUIView _overlayView;
public void PresentHelpOverlay()
{
RectangleF windowFullFrame = new RectangleF(0,0,UIScreen.MainScreen.Bounds.Width,UIScreen.MainScreen.Bounds.Height);
// Conversion?
//[aView convertPoint:localPosition toView:nil];
RectangleF overlayFrame = View.ConvertRectFromView(windowFullFrame ,null);
// Clear old one if it exists.
if (_overlayView != null) _overlayView = null;
// Instantiate popup view and add to (in this case the 2nd tier view). This is in an abstract class, if in a concrete one it'd normally just be View.Add
_overlayView = new HelpOverlayUIView(this, overlayFrame);
// tried th, didn't change it.
// this.WantsFullScreenLayout = true;
// _childView.BringSubviewToFront(_overlayView);
_overlayView.Alpha = 0;
_childView.Add (_overlayView);
// Setup event to close without doing anything.
_overlayView.CloseView += (sender, e) => {
Console.WriteLine ("close called");
// animate modal popup's departure
UIView.Animate (
0.5f,
() => {
// Anim Code
_overlayView.Alpha = 0;
},
null
);
};
// animate modal popup's arrival
UIView.Animate (
0.5f,
() => {
// Anim Code
_overlayView.Alpha = 1;
},
null
);
}
(The view is just a UIView with an overload to the Draw() method that places text etc into the view)

Answer 1

You could add the _overlayView to something higher up in the view hierarchy such as the NavigationViewController. If your NavigationViewController is set to be your RootViewController (well, regardless of what is really) you could try this.
((AppDelegate)UIApplication.SharedApplication.Delegate).Window.RootViewController.Add(_overlayView);
You can also bring a subview to the front like this, but this is only to the front of that view, not to the front of everything (which isn't really what you wanted unless _childView was your NavigationViewController).
_childView.BringSubviewToFront(_overlayView);