Problem with NavigationItem RightBarButtonItem after last update - xamarin.ios

Question

After the last update (4.0.0) I am having an issue and was wondering of this is a bug and is there a fix.
As you can see from the code below, I am creating a NavigationItem.RightBarButtonItem and adding a delegate to the TouchUpInside event. The button is created but when the touch occurs, the app dies a horribly(see below). Before this update the code ran perfect.
Anyone has any idea? Monotouch team, are you aware of this issue? Maybe I just coded incorrectly and worked before, but the new update has proven I was coding incorrect.
Regards,
Danny
CODE
//start by creating the view
RectangleF f = new RectangleF(0f,0f,38f,38f);
UIView v = new UIView(f);
//Now create a button with a background
UIButton b = new UIButton(f);
b.SetBackgroundImage(UIImage.FromFile("Images/Common/info.png"),UIControlState.Normal);
//add the button to the view
v.Add(b);
b.TouchUpInside
//give teh button a delegate action
b.TouchUpInside += delegate {
//var vc3 = new iPhone_HomeView();
//var vc3 = new iPhone_RetardView();
//vc3.Title = "asdasd";
//this.NavigationController.PushViewController (vc3, true);
};
//now apply the view to the navigation bar on the right
NavigationItem.RightBarButtonItem = new UIBarButtonItem(v);
NavigationItem.RightBarButtonItem.Width = 38f;
ERROR
Stacktrace:
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication.UIApplicationMain (int,string[],intptr,intptr)
at MonoTouch.UIKit.UIApplication.Main (string[],string,string) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26
at MonoTouch.UIKit.UIApplication.Main (string[]) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31
at SmartPhoneSolution.Application.Main (string[]) [0x00000] in /Users/aprdev/Projects/SmartPhoneSolution/SmartPhoneSolution/Main.cs:15
at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr)
Native stacktrace:
0 SmartPhoneSolution1 0x000d0db5 mono_handle_native_sigsegv + 343
1 SmartPhoneSolution1 0x0000f80c mono_sigsegv_signal_handler + 322
2 libSystem.B.dylib 0x996fb45b _sigtramp + 43
3 ??? 0xffffffff 0x0 + 4294967295
4 UIKit 0x01b92de0 -[UIControl sendAction:to:forEvent:] + 67
5 UIKit 0x01b95262 -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 527
6 UIKit 0x01b93e0f -[UIControl touchesEnded:withEvent:] + 458
7 UIKit 0x01b2b3d0 -[UIWindow _sendTouchesForEvent:] + 567
8 UIKit 0x01b0ccb4 -[UIApplication sendEvent:] + 447
9 UIKit 0x01b119bf _UIApplicationHandleEvent + 7672
10 GraphicsServices 0x05768822 PurpleEventCallback + 1550
11 CoreFoundation 0x00debff4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
12 CoreFoundation 0x00d4c807 __CFRunLoopDoSource1 + 215
13 CoreFoundation 0x00d49a93 __CFRunLoopRun + 979
14 CoreFoundation 0x00d49350 CFRunLoopRunSpecific + 208
15 CoreFoundation 0x00d49271 CFRunLoopRunInMode + 97
16 GraphicsServices 0x0576700c GSEventRunModal + 217
17 GraphicsServices 0x057670d1 GSEventRun + 115
18 UIKit 0x01b15af2 UIApplicationMain + 1160
19 ??? 0x0ba72744 0x0 + 195503940
20 ??? 0x0ba7267a 0x0 + 195503738
21 ??? 0x090bfb9e 0x0 + 151780254
22 ??? 0x090bfaea 0x0 + 151780074
23 ??? 0x090bfb75 0x0 + 151780213
24 SmartPhoneSolution1 0x0000f5c7 mono_jit_runtime_invoke + 1332
25 SmartPhoneSolution1 0x001ed281 mono_runtime_invoke + 137
26 SmartPhoneSolution1 0x001ef968 mono_runtime_exec_main + 669
27 SmartPhoneSolution1 0x001eed52 mono_runtime_run_main + 843
28 SmartPhoneSolution1 0x000a3153 mono_jit_exec + 200
29 SmartPhoneSolution1 0x002a16b8 main + 4155
30 SmartPhoneSolution1 0x00002949 _start + 208
31 SmartPhoneSolution1 0x00002878 start + 40
Debug info from gdb:
/tmp/mono-gdb-commands.WL0ypx:1: Error in sourced command file:
unable to debug self
=================================================================
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object
at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:26
at MonoTouch.UIKit.UIApplication.Main (System.String[] args) [0x00000] in /Users/plasma/Source/iphone/monotouch/UIKit/UIApplication.cs:31
at SmartPhoneSolution.Application.Main (System.String[] args) [0x00000] in /Users/aprdev/Projects/SmartPhoneSolution/SmartPhoneSolution/Main.cs:15

Answer 1

I had a similar problem last week. It seems like MT 4 is more aggressive in it's GC than earlier versions, and things that I was able to get away with before are now causing problems.
Try declaring your UIButton at the class level, instead of scoping it locally.

Answer 2

Same thing happened to me porting existing Objective-C code. This solution is to make sure your button is an instance member of your class. This code works well (extra viewcontroller boilerplate code omitted):
public partial class HomeViewController : UIViewController
{
private UIButton _settingsButton;
public override void ViewDidLoad()
{
base.ViewDidLoad();
ConfigureNavigationBar();
}
private void ConfigureNavigationBar()
{
// Add the Settings icon to nav bar
_settingsButton = UIButton.FromType(UIButtonType.Custom);
_settingsButton.SetImage(UIImage.FromBundle("Images/settings.png"),
UIControlState.Normal);
_settingsButton.SizeToFit();
_settingsButton.TouchUpInside += (sender, e) =>
Console.WriteLine("clicked");
this.NavigationItem.RightBarButtonItem =
new UIBarButtonItem(_settingsButton);
}
}
See the last paragraph ("When to Keep References to Objects") in the MonoTouch documentation: API Design