In my ViewModel I have a property called 'Objects' which is an ObservableCollection.
When I setup the ListView it is as such:
ObjectList = new ListView()
{
IsPullToRefreshEnabled = true,
HasUnevenRows = ViewModel.HasUnevenRows,
RefreshCommand = ViewModel.LoadObjects,
ItemsSource = ViewModel.Objects,
ItemTemplate = new DataTemplate(ViewModel.ListViewItem),
BindingContext = ViewModel
};
ObjectList.SetBinding(ListView.IsRefreshingProperty, new Binding("IsLoading"));
My ViewModel has an IsLoading property and I am making sure I'm not reloading the list while it is already being loaded via the command CanExecute:
LoadObjects = new Command(() => { ListObjects(); },() => { return !IsLoading; });
When I pull to refresh it executes the LoadObjects command.
The issue I am encountering is when I pull to refresh the list, after the 3rd or 4th time it will crash with this:
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at Xamarin.Forms.Platform.iOS.LabelRenderer.UpdateText () [0x00070] in <8f7e3b9d1483403590c8ab3d78cce1ac>:0
at Xamarin.Forms.Platform.iOS.LabelRenderer.OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00097] in <8f7e3b9d1483403590c8ab3d78cce1ac>:0
at (wrapper delegate-invoke) <Module>:invoke_void_object_PropertyChangedEventArgs (object,System.ComponentModel.PropertyChangedEventArgs)
at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x0000a] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:137
at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:388
at Xamarin.Forms.BindableObject.SetValueActual (Xamarin.Forms.BindableProperty property, Xamarin.Forms.BindableObject+BindablePropertyContext context, System.Object value, System.Boolean currentlyApplying, Xamarin.Forms.Internals.SetValueFlags attributes, System.Boolean silent) [0x000f4] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:593
at Xamarin.Forms.BindableObject.SetValueCore (Xamarin.Forms.BindableProperty property, System.Object value, Xamarin.Forms.Internals.SetValueFlags attributes, Xamarin.Forms.BindableObject+SetValuePrivateFlags privateAttributes) [0x0015b] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:390
at Xamarin.Forms.BindingExpression.ApplyCore (System.Object sourceObject, Xamarin.Forms.BindableObject target, Xamarin.Forms.BindableProperty property, System.Boolean fromTarget) [0x001f9] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindingExpression.cs:174
at Xamarin.Forms.BindingExpression.Apply (System.Object sourceObject, Xamarin.Forms.BindableObject target, Xamarin.Forms.BindableProperty property) [0x0006b] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindingExpression.cs:77
at Xamarin.Forms.Binding.Apply (System.Object newContext, Xamarin.Forms.BindableObject bindObj, Xamarin.Forms.BindableProperty targetProperty) [0x00042] in C:\agent\_work\3\s\Xamarin.Forms.Core\Binding.cs:126
at Xamarin.Forms.BindableObject.ApplyBindings (System.Boolean skipBindingContext) [0x0003b] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:421
at Xamarin.Forms.BindableObject.ApplyBindings () [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:125
at Xamarin.Forms.BindableObject.SetInheritedBindingContext (Xamarin.Forms.BindableObject bindable, System.Object value) [0x0005a] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:119
at Xamarin.Forms.Element.SetChildInheritedBindingContext (Xamarin.Forms.Element child, System.Object context) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:498
at Xamarin.Forms.Element.OnBindingContextChanged () [0x00021] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:341
at Xamarin.Forms.View.OnBindingContextChanged () [0x00042] in C:\agent\_work\3\s\Xamarin.Forms.Core\View.cs:99
at Xamarin.Forms.BindableObject.SetInheritedBindingContext (Xamarin.Forms.BindableObject bindable, System.Object value) [0x00060] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:120
at Xamarin.Forms.Element.SetChildInheritedBindingContext (Xamarin.Forms.Element child, System.Object context) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:498
at Xamarin.Forms.Element.OnBindingContextChanged () [0x00021] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:341
at Xamarin.Forms.View.OnBindingContextChanged () [0x00042] in C:\agent\_work\3\s\Xamarin.Forms.Core\View.cs:99
at Xamarin.Forms.BindableObject.SetInheritedBindingContext (Xamarin.Forms.BindableObject bindable, System.Object value) [0x00060] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:120
at Xamarin.Forms.Element.SetChildInheritedBindingContext (Xamarin.Forms.Element child, System.Object context) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:498
at Xamarin.Forms.Element.OnBindingContextChanged () [0x00021] in C:\agent\_work\3\s\Xamarin.Forms.Core\Element.cs:341
at Xamarin.Forms.Cell.OnBindingContextChanged () [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\Cells\Cell.cs:114
at Xamarin.Forms.BindableObject.BindingContextPropertyChanged (Xamarin.Forms.BindableObject bindable, System.Object oldvalue, System.Object newvalue) [0x0000e] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:441
at Xamarin.Forms.BindableObject.SetValueActual (Xamarin.Forms.BindableProperty property, Xamarin.Forms.BindableObject+BindablePropertyContext context, System.Object value, System.Boolean currentlyApplying, Xamarin.Forms.Internals.SetValueFlags attributes, System.Boolean silent) [0x00108] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:596
at Xamarin.Forms.BindableObject.SetValueCore (Xamarin.Forms.BindableProperty property, System.Object value, Xamarin.Forms.Internals.SetValueFlags attributes, Xamarin.Forms.BindableObject+SetValuePrivateFlags privateAttributes) [0x0015b] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:390
at Xamarin.Forms.BindableObject.SetValue (Xamarin.Forms.BindableProperty property, System.Object value, System.Boolean fromStyle, System.Boolean checkAccess) [0x0005f] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:543
at Xamarin.Forms.BindableObject.SetValue (Xamarin.Forms.BindableProperty property, System.Object value) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:83
at Xamarin.Forms.BindableObject.set_BindingContext (System.Object value) [0x00000] in C:\agent\_work\3\s\Xamarin.Forms.Core\BindableObject.cs:24
at Xamarin.Forms.Internals.TemplatedItemsList`2+<UnhookItem>d__154[TView,TItem].MoveNext () [0x000b0] in C:\agent\_work\3\s\Xamarin.Forms.Core\TemplatedItemsList.cs:1217
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/11.2.0.11/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:151
at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/11.2.0.11/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018
at UIKit.UIKitSynchronizationContext+<Post>c__AnonStorey0.<>m__0 () [0x00000] in /Users/builder/data/lanes/5481/2f8bbec0/source/xamarin-macios/src/UIKit/UIKitSynchronizationContext.cs:24
at Foundation.NSAsyncActionDispatcher.Apply () [0x00000] in /Users/builder/data/lanes/5481/2f8bbec0/source/xamarin-macios/src/Foundation/NSAction.cs:163
--- End of stack trace from previous location where exception was thrown ---
at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Users/builder/data/lanes/5481/2f8bbec0/source/xamarin-macios/src/UIKit/UIApplication.cs:79
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/5481/2f8bbec0/source/xamarin-macios/src/UIKit/UIApplication.cs:63
at HydrusCRM.iOS.Application.Main (System.String[] args) [0x00001] in /Volumes/Data/Apps/HydrusCRM/iOS/Main.cs:17
Here is the code that updates the objects collection:
var result = (IList)JsonConvert.DeserializeObject(results, listType);
if (result.Count > 0)
{
Device.BeginInvokeOnMainThread(() =>
{
foreach (Models.Objects.Model @object in result)
{
objects.Add(@object);
}
});
}
I am not sure where the issue is coming from as none of my apps code is in the exception stack.
), and I am going to build an app. I would use Xamarin.Forms to reach all the target app stores. Now, my problem is... what happens when a user loads my website on their device/workstation? Websites (or web applications) are obviously rendered in HTML5/JavaScript these days. This is something that Xamarin.Forms (as awesome as it is) does not do, currently (as far as I know). And so, I have been wondering if this is a known issue, and (more importantly) a known/possible direction for Xamarin.Forms.