Xamarin Android - Run time crash - [libc] Fatal signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 0x7ffb9b4f40 in tid 32564 (companyname.app), pid 32564 (companyname.app)

Question

I am creating an app for Android in Xamarin Forms (latest) on Visual Studio. On my Android 12.1 emulator, it works fine, whether I use Target Framework as 12, 11, or 10.
But on my actual smartphone (API level 10), and on another smartphone (API level 7), it seems to crash as soon as I run this function -

        void Browsing(object sender)  
        {  
            Browser.Children.Clear();  
              
            FocusedItem = null;  
              
            CurrentFolder.Insert(0, ((sender as Frame).BindingContext as FolderFunctionality.Item).Name);  
  
            FolderFunctionality.Item Folder = FolderFunctionality.Get(CurrentFolder.GetRange(1, CurrentFolder.Count - 1), CurrentFolder[0]);  
  
            foreach (FolderFunctionality.Item a in Folder)  
            {  
                Frame button = new Frame  
                {  
                    Padding = 10,  
                    CornerRadius = 15,  
                    HasShadow = false,  
                    BackgroundColor = Color.LightSkyBlue,  
                    Content = new StackLayout  
                    {  
                        HorizontalOptions = LayoutOptions.FillAndExpand,  
                        Orientation = StackOrientation.Horizontal,  
                        Padding = 0,  
                        Spacing = 10,  
                        Children =  
                        {  
                            new Image { BackgroundColor = Color.Transparent, VerticalOptions = LayoutOptions.Center, HorizontalOptions = LayoutOptions.Start, HeightRequest = 50, WidthRequest = 50, Source = ImageSource.FromResource("App.Resources.Devices." + a.Type + ".png", typeof(App)) },  
                            new Label { BackgroundColor = Color.Transparent, VerticalOptions = LayoutOptions.Center, HorizontalOptions = LayoutOptions.FillAndExpand, LineBreakMode = LineBreakMode.TailTruncation, TextColor = Color.Black, Padding = 0, FontSize = 20, Text = a.Name },  
                        }  
                    }  
                };  
                TapGestureRecognizer tap = new TapGestureRecognizer();  
  
                button.BindingContext = a;  
  
                if (a.Type == "F") tap.Tapped += (snd, arg) =>  
                {  
                    PreviouslyFocusedItem.BackgroundColor = Color.LightSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.TailTruncation;  
  
                    PreviouslyFocusedItem = snd as Frame;  
  
                    bool UnFocus = !(snd as Frame).HasShadow;  
                    Delays.Cancel();  
                    Delays.Dispose();  
                    Delays = new CancellationTokenSource();  
  
                    PreviouslyFocusedItem.BackgroundColor = Color.DeepSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.WordWrap;  
  
                    if (UnFocus)  
                    {  
                        FocusedItem = ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).Text;  
                        Task.Run(async () =>  
                        {  
                            try { await Task.Delay(500, Delays.Token); } catch (OperationCanceledException) { }  
                            PreviouslyFocusedItem.HasShadow = false;  
                        });  
                        (snd as Frame).HasShadow = true;  
                    }  
                    else Browsing(snd);  
                };  
                else tap.Tapped += (snd, arg) =>  
                {  
                    PreviouslyFocusedItem.BackgroundColor = Color.LightSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.TailTruncation;  
  
                    PreviouslyFocusedItem = snd as Frame;  
  
                    bool UnFocus = !(snd as Frame).HasShadow;  
                    Delays.Cancel();  
                    Delays.Dispose();  
                    Delays = new CancellationTokenSource();  
  
                    PreviouslyFocusedItem.BackgroundColor = Color.DeepSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.WordWrap;  
  
                    if (UnFocus)  
                    {  
                        FocusedItem = ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).Text;  
                        Task.Run(async () =>  
                        {  
                            try { await Task.Delay(500, Delays.Token); } catch (OperationCanceledException) { }  
                            PreviouslyFocusedItem.HasShadow = false;  
                        });  
                        (snd as Frame).HasShadow = true;  
                    }  
                    else DeviceController(snd);  
                };  
  
                button.GestureRecognizers.Add(tap);  
                Browser.Children.Add(button);  
            }  
  
            if (Browser.Children.Count < 1) Browser.Children.Add(new Label { Text = "No Items Here", BindingContext = new FolderFunctionality.Item() });  
  
            maincontent.Content = new ScrollView { Content = Browser, HorizontalScrollBarVisibility = ScrollBarVisibility.Never };  
            topbar.Content = new StackLayout  
            {  
                Padding = new Thickness(8, 4),  
                Spacing = 0,  
                BackgroundColor = Color.Transparent,  
                Orientation = StackOrientation.Horizontal,  
                Children =  
                {  
                    backbutton,  
                    AppName,  
                    new Frame { Padding = 0, WidthRequest = 62, HeightRequest = 62, BackgroundColor = Color.Transparent }  
                }  
            };  
            MainPage = new ContentPage                                                              // Main Page  
            {  
                Opacity = 0,  
                Content = new StackLayout  
                {  
                    Spacing = 0,  
                    Children =  
                    {  
                        topbar,  
                        maincontent,  
                        ChangeOptions  
                    }  
                }  
            };  
  
            MainPage.FadeTo(1);  
        }  

Where FolderFunctionality and FolderFunctionality.Item is a class created by me (Very less chances that it causes problems as another function using it in the same way runs as expected).

The console shows this message last -
[libc] Fatal signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 0x7ffb9b4f40 in tid 32564 (companyname.app), pid 32564 (companyname.app)

Any ideas about the solution will be highly appreciated.

Answer 1

I think the problem is -
'Browsing()' is called as a part of a button click event which is a child of Browser'. And, Browser's children are being cleared in 'Browsing()' itself.
So, I guess the button object is destroyed before 'Browsing' finishes, and the nulls it out.
Here is how Browsing() is called...

tap.Tapped += (snd, arg) =>  
                {  
                    PreviouslyFocusedItem.BackgroundColor = Color.LightSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.TailTruncation;  
  
                    PreviouslyFocusedItem = snd as Frame;  
  
                    bool UnFocus = !(snd as Frame).HasShadow;  
                    Delays.Cancel();  
                    Delays.Dispose();  
                    Delays = new CancellationTokenSource();  
  
                    PreviouslyFocusedItem.BackgroundColor = Color.DeepSkyBlue;  
                    ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).LineBreakMode = LineBreakMode.WordWrap;  
  
                    if (UnFocus)  
                    {  
                        FocusedItem = ((PreviouslyFocusedItem.Content as StackLayout).Children[1] as Label).Text;  
                        Task.Run(async () =>  
                        {  
                            try { await Task.Delay(500, Delays.Token); } catch (OperationCanceledException) { }  
                            PreviouslyFocusedItem.HasShadow = false;  
                        });  
                        (snd as Frame).HasShadow = true;  
                    }  
                    else Browsing(snd);  
                };  

Am I correct, and if so, can you tell me the possible solution?