Forum Xamarin.iOS

App crashing on iOS 7 and iPhone 5

GauravSGauravS USMember

I am building an app where there are some dynamically generated buttons in table view cells. Everything is working fine on iPhone 4 & 4S. However after a few repetitions of the workflow, on clicking a button in table, the app crashes without giving any information in the debugger. This is happening consistently. Only once I got an exception with details as:

System.Exception: Failed to marshal the Objective-C object 0x19972ac0 (type: MonoTouch.UIKit.UIControlEventProxy). Could not find an existing managed instance for this object, nor was it possible to create a new managed instance (because the type 'MonoTouch.UIKit.UIControlEventProxy' does not have a constructor that takes one IntPtr argument).
  at MonoTouch.ObjCRuntime.Runtime.MissingCtor (IntPtr ptr, IntPtr klass, System.Type type, MissingCtorResolution resolution) [0x00046] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/.pp-Runtime.cs:352
  at MonoTouch.ObjCRuntime.Runtime.ConstructNSObject[NSObject] (IntPtr ptr, System.Type type, MissingCtorResolution missingCtorResolution) [0x00000] in <filename unknown>:0
  at MonoTouch.ObjCRuntime.Runtime.GetNSObject (IntPtr ptr, System.Type target_type, MissingCtorResolution missingCtorResolution, System.Boolean& created) [0x00073] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/.pp-Runtime.cs:514
  at MonoTouch.ObjCRuntime.Runtime.GetNSObjectWrapped (IntPtr ptr, IntPtr type_ptr, System.Boolean& created) [0x0000c] in /Developer/MonoTouch/Source/monotouch/src/ObjCRuntime/.pp-Runtime.cs:686
  at at (wrapper native-to-managed) MonoTouch.ObjCRuntime.Runtime:GetNSObjectWrapped (intptr,intptr,int&)
  at 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) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/.pp-UIApplication.cs:38
  at DominosOET.Application.Main (System.String[] args) [0x00008] in /Users/juligupta/TFS Workspace/OET/DominosOET/Main.cs:16

This is happening on a combination of iOS 7 and iPhone 5. Can anyone shed some light on what might be causing this. I am not getting any info in the debugger.


  • RolfBjarneKvingeRolfBjarneKvinge USXamarin Team Xamurai

    Most likely the dynamically created buttons were freed by the GC, and thus freeing the event handler as well.

    One possible solution is to use a custom UIButton subclass instead of UIButton itself (this works because Xamarin.iOS treats subclasses differently than the framework types themselves). Could you try this and see if it helps?

  • GauravSGauravS USMember

    Thanks for the quick response.
    It worked!!!
    And the app is running smoothly again. Thanks a lot for your help.

  • OvidiuAdorianOvidiuAdorian USMember

    And if you want to use a button on table row?
    How do you do this?

  • kunalthakkarkunalthakkar INMember ✭✭

    @Gaurav Could you please post some code that would be useful for me.

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