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1. When switching between the tabs/pages too fast I get a NullReferenceException (at Xamarin.Forms.Platform.iOS.Platform.GetRenderer).
2. I couldn't figure out when this happens exactly but after frequently switching between the tabs/pages the toolbar items of one or more pages just disappear.
I attached a test project which shows these issues on the simulator and on my test device (5th gen. iPod).
Created attachment 13993 [details]
I finally found out when the toolbar items disappear!
Just tap the currently selected tab again, select a different tab/page and when you go back to the previous page the toolbar items are gone.
Same issue here.
The disappearing toolbar icons are the first symptom of the problem.
After more clicks on the tabs the app finally crashes.
Here's the stacktrace of the NullReferenceException, caught in main.cs:
at Xamarin.Forms.Platform.iOS.Platform.GetRenderer (Xamarin.Forms.VisualElement bindable) [0x00000] in <filename unknown>:0
at Xamarin.Forms.Platform.iOS.NavigationRenderer.GetAppearedOrDisappearedTask (Xamarin.Forms.Page page) [0x00011] in <filename unknown>:0
at Xamarin.Forms.Platform.iOS.NavigationRenderer.RemoveViewControllers (Boolean animated) [0x00048] in <filename unknown>:0
at Xamarin.Forms.Platform.iOS.NavigationRenderer.PopToRootViewController (Boolean animated) [0x00008] in <filename unknown>:0
at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string,intptr,intptr)
at UIKit.UIApplication.Main (System.String args, IntPtr principal, IntPtr delegate) [0x00005] in /Users/builder/data/lanes/2377/73229919/source/maccore/src/UIKit/UIApplication.cs:77
at UIKit.UIApplication.Main (System.String args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/2377/73229919/source/maccore/src/UIKit/UIApplication.cs:61
at MyTestApp.iOS.Application.Main (System.String args) [0x00009] in /Users/me/Projects/Xamarin/My_Apps/MyTestApp/iOS/Main.cs:20
This already happened in Xamarin Forms 1.5 and is still happening in 2.0.
IMHO this has nothing to do with clicking on the TABs too fast, it just happens after clicking often enough on different tabs (which obviously happens sooner the faster you tap :)
Should be fixed in 2.0.2-pre1
Correction should be fixed in 2.1.0-pre1
Just to be certain,
do you really mean 2.1.0 or was it a type and you meant 2.0.1?
After my tests it's not fixed in 2.0.1.
I have checked this issue with Xamarin.Forms 18.104.22.16803-pre2 and now its working fine.
Hence closing this issue.
I can verify that this is fixed in 2.1.