RadListView causes crash when PropertyGroupDescriptor has nulls

[Aaron]

Looks like a bug to me in version 2017.1.1220.233...

The Issue

Here is my model, I have a collection of these;

public class Site
{
    public int SiteId { get; set; }
    public string SiteName { get; set; }
    public string SiteDetailText { get; set; }
    public string FarmName { get; set; }
}

 

Here is the XAML definition of the RadListView;

<telerikui:RadListView x:Name="SitesList" ItemsSource="{Binding MySites}">
    <telerikui:RadListView.ItemTemplate>
        <DataTemplate>
                    <listView:ListViewTemplateCell>
                                <listView:ListViewTemplateCell.View>
                                    <Grid Padding="5">
                                        <Grid.RowDefinitions>
                                            <RowDefinition Height="Auto" />
                                            <RowDefinition Height="Auto" />
                                        </Grid.RowDefinitions>

                                        <Label Grid.Row="0" Text="{Binding SiteName}" FontSize="Large" />
                                        <Label Grid.Row="1" Text="{Binding SiteDetailText}" />
                                    </Grid>
                            </listView:ListViewTemplateCell.View>
                    </listView:ListViewTemplateCell>
                </DataTemplate>
    </telerikui:RadListView.ItemTemplate>

            <!-- this doesn't work -->
            <telerikui:RadListView.GroupDescriptors>
              <listView:PropertyGroupDescriptor PropertyName="FarmName" />
             </telerikui:RadListView.GroupDescriptors>


</telerikui:RadListView>

 

I get the collection of Site models from a JSON string, and sometimes the FarmName property is missing, meaning FarmName is null. When I run the application this exception is thrown;

03-23 12:08:52.176 I/MonoDroid( 4852): UNHANDLED EXCEPTION:
03-23 12:08:52.180 I/MonoDroid( 4852): System.ArgumentException: The default comparer works with elements that implement IComparable interface.
03-23 12:08:52.180 I/MonoDroid( 4852):   at (wrapper managed-to-native) Java.Interop.NativeMethods:java_interop_jnienv_call_nonvirtual_void_method_a (intptr,intptr&,intptr,intptr,intptr,Java.Interop.JniArgumentValue*)
03-23 12:08:52.180 I/MonoDroid( 4852):   at Java.Interop.JniEnvironment+InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x0008f] in /Users/builder/data/lanes/4009/9578cdcd/source/Java.Interop/src/Java.Interop/Java.Interop/JniEnvironment.g.cs:12079 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Android.Runtime.JNIEnv.CallNonvirtualVoidMethod (System.IntPtr jobject, System.IntPtr jclass, System.IntPtr jmethod, Android.Runtime.JValue* parms) [0x00000] in /Users/builder/data/lanes/4009/9578cdcd/source/monodroid/src/Mono.Android/JNIEnv.g.cs:444 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Com.Telerik.Widget.List.ListViewAdapter.set_Items (System.Collections.IList value) [0x0009d] in <4ab376ccf3e94543ba940e1beffd5307>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewDataSourceAdapterExtensions.SetSource (Com.Telerik.Widget.List.ListViewDataSourceAdapter adapter, System.Collections.IEnumerable source) [0x00007] in <0283f7990ca1485d8a9efc5b1581ce6f>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewAdapter.UpdateItemsSource (Telerik.XamarinForms.DataControls.RadListView sourceOwner, Com.Telerik.Widget.List.RadListView targetOwner) [0x00011] in <0283f7990ca1485d8a9efc5b1581ce6f>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewAdapter.UpdateCore (Telerik.XamarinForms.DataControls.RadListView sourceOwner, Com.Telerik.Widget.List.RadListView targetOwner, System.String propertyName) [0x0004b] in <0283f7990ca1485d8a9efc5b1581ce6f>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.Common.FacadeAdapterBase`2[S,T].Update (System.Object sourceOwner, System.Object targetOwner, System.String propertyName, System.Object sourceOwnerRoot, System.Object targetOwnerRoot) [0x00000] in <41a54de86ddf4ac5b8f46f7114ddd5ec>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.Common.XamarinToNativeControlExtensions.Update[T,K] (T nativeElement, K xfЕlement, System.String propertyName, System.Object sourceOwnerRoot, System.Object targetOwnerRoot) [0x0002b] in <41a54de86ddf4ac5b8f46f7114ddd5ec>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewRenderer.OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00023] in <0283f7990ca1485d8a9efc5b1581ce6f>:0 
03-23 12:08:52.180 I/MonoDroid( 4852):   at (wrapper delegate-invoke) <Module>:invoke_void_object_PropertyChangedEventArgs (object,System.ComponentModel.PropertyChangedEventArgs)
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x0000a] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindableObject.cs:137 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\Element.cs:379 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindableObject.SetValueActual (Xamarin.Forms.BindableProperty property, Xamarin.Forms.BindableObject+BindablePropertyContext context, System.Object value, System.Boolean currentlyApplying, Xamarin.Forms.BindableObject+SetValueFlags attributes, System.Boolean silent) [0x000f4] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindableObject.cs:581 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindableObject.SetValueCore (Xamarin.Forms.BindableProperty property, System.Object value, Xamarin.Forms.BindableObject+SetValueFlags attributes, Xamarin.Forms.BindableObject+SetValuePrivateFlags privateAttributes) [0x0014b] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindableObject.cs:378 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindingExpression.ApplyCore (System.Object sourceObject, Xamarin.Forms.BindableObject target, Xamarin.Forms.BindableProperty property, System.Boolean fromTarget) [0x001f9] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindingExpression.cs:173 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindingExpression.Apply (System.Boolean fromTarget) [0x0003e] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindingExpression.cs:55 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Xamarin.Forms.BindingExpression+BindingExpressionPart.<PropertyChanged>b__47_0 () [0x00000] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Core\BindingExpression.cs:542 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Java.Lang.Thread+RunnableImplementor.Run () [0x0000b] in /Users/builder/data/lanes/4009/9578cdcd/source/xamarin-android/src/Mono.Android/Java.Lang/Thread.cs:36 
03-23 12:08:52.180 I/MonoDroid( 4852):   at Java.Lang.IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this) [0x00009] in /Users/builder/data/lanes/4009/9578cdcd/source/monodroid/src/Mono.Android/platforms/android-25/src/generated/Java.Lang.IRunnable.cs:81 
03-23 12:08:52.180 I/MonoDroid( 4852):   at (wrapper dynamic-method) System.Object:7de252d4-c417-4d4a-8229-509ea6b9512e (intptr,intptr)

The Fix

If I remove the <RadListView.GroupDescriptors> from the XAML this works fine...

Also, It works without crashing if I change the definition of the FarmName property to have a default value;

public string FarmName { get; set; } = "No Farm"

 

Can we please have it so the List can handle these null values gracefully (empty string maybe)? Either that or show a clearer error message. I've spent 4 hours trying to get this grouping working, and until I stumbled across the stack trace for the IComparer exception I was struggling to figure out where to start.

Cheers

[Aaron]

I suspect this is an issue in latest stable version also

[Aaron]

confirmed busted in 2017.1.10321.233

different stack trace through;

 

03-23 12:35:57.793 I/MonoDroid( 6825): UNHANDLED EXCEPTION:
03-23 12:35:57.833 I/MonoDroid( 6825): Java.Lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Object.hashCode()' on a null object reference
03-23 12:35:57.833 I/MonoDroid( 6825):   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/4009/f3074d2c/source/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
03-23 12:35:57.833 I/MonoDroid( 6825):   at Java.Interop.JniEnvironment+InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x000a7] in /Users/builder/data/lanes/4009/9578cdcd/source/Java.Interop/src/Java.Interop/Java.Interop/JniEnvironment.g.cs:12083 
03-23 12:35:57.834 I/MonoDroid( 6825):   at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeNonvirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x00022] in /Users/builder/data/lanes/4009/9578cdcd/source/Java.Interop/src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs:41 
03-23 12:35:57.834 I/MonoDroid( 6825):   at Android.Views.ViewGroup.Layout (System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x00055] in /Users/builder/data/lanes/4009/9578cdcd/source/monodroid/src/Mono.Android/platforms/android-25/src/generated/Android.Views.ViewGroup.cs:3188 
03-23 12:35:57.834 I/MonoDroid( 6825):   at Xamarin.Forms.Platform.Android.ViewRenderer`2[TView,TNativeView].OnLayout (System.Boolean changed, System.Int32 l, System.Int32 t, System.Int32 r, System.Int32 b) [0x00059] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Platform.Android\ViewRenderer.cs:137 
03-23 12:35:57.834 I/MonoDroid( 6825):   at Xamarin.Forms.Platform.Android.FormsViewGroup.n_OnLayout_ZIIII (System.IntPtr jnienv, System.IntPtr native__this, System.Boolean p0, System.Int32 p1, System.Int32 p2, System.Int32 p3, System.Int32 p4) [0x00008] in C:\BuildAgent3\work\ca3766cfc22354a1\Xamarin.Forms.Platform.Android.FormsViewGroup\obj\Release\generated\src\Xamarin.Forms.Platform.Android.FormsViewGroup.cs:240 
03-23 12:35:57.834 I/MonoDroid( 6825):   at (wrapper dynamic-method) System.Object:6c49126f-8cc4-4eaa-bbfb-45bbd82d2026 (intptr,intptr,bool,int,int,int,int)
03-23 12:35:57.834 I/MonoDroid( 6825):   --- End of managed Java.Lang.NullPointerException stack trace ---
03-23 12:35:57.834 I/MonoDroid( 6825): java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Object.hashCode()' on a null object reference
03-23 12:35:57.834 I/MonoDroid( 6825): at com.telerik.widget.list.ListViewAdapter.getItemId(ListViewAdapter.java:351)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.telerik.widget.list.ListViewDataSourceAdapter.getItemId(ListViewDataSourceAdapter.java:396)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.telerik.widget.list.ListViewWrapperAdapter.getItemId(ListViewWrapperAdapter.java:413)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4667)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4617)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1994)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1390)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1353)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:574)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3028)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2906)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3283)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.telerik.widget.list.RadListView.onLayout(RadListView.java:561)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.ViewRenderer_2.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.ViewRenderer_2.onLayout(ViewRenderer_2.java:47)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.xamarin.forms.platform.android.FormsViewGroup.measureAndLayout(FormsViewGroup.java:29)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.onLayout(VisualElementRenderer_1.java:49)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.xamarin.forms.platform.android.FormsViewGroup.measureAndLayout(FormsViewGroup.java:29)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.onLayout(VisualElementRenderer_1.java:49)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.xamarin.forms.platform.android.FormsViewGroup.measureAndLayout(FormsViewGroup.java:29)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.VisualElementRenderer_1.onLayout(VisualElementRenderer_1.java:49)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.xamarin.forms.platform.android.FormsViewGroup.measureAndLayout(FormsViewGroup.java:29)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.NavigationPageRenderer.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.NavigationPageRenderer.onLayout(NavigationPageRenderer.java:65)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at com.xamarin.forms.platform.android.FormsViewGroup.measureAndLayout(FormsViewGroup.java:29)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.MasterDetailContainer.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.MasterDetailContainer.onLayout(MasterDetailContainer.java:53)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1187)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.MasterDetailPageRenderer.n_onLayout(Native Method)
03-23 12:35:57.834 I/MonoDroid( 6825): at md5270abb39e60627f0f200893b490a1ade.MasterDetailPageRenderer.onLayout(MasterDetailPageRenderer.java:68)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.834 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.PlatformRenderer.n_onLayout(Native Method)
03-23 12:35:57.835 I/MonoDroid( 6825): at md5b60ffeb829f638581ab2bb9b1a7f4f3f.PlatformRenderer.onLayout(PlatformRenderer.java:63)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
03-23 12:35:57.835 I/MonoDroid( 6825): at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2678)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.View.layout(View.java:16630)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewGroup.layout(ViewGroup.java:5437)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2171)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1931)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.Choreographer.doCallbacks(Choreographer.java:670)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.Choreographer.doFrame(Choreographer.java:606)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.os.Handler.handleCallback(Handler.java:739)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.os.Handler.dispatchMessage(Handler.java:95)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.os.Looper.loop(Looper.java:148)
03-23 12:35:57.835 I/MonoDroid( 6825): at android.app.ActivityThread.main(ActivityThread.java:5417)
03-23 12:35:57.835 I/MonoDroid( 6825): at java.lang.reflect.Method.invoke(Native Method)
03-23 12:35:57.835 I/MonoDroid( 6825): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
03-23 12:35:57.835 I/MonoDroid( 6825): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

initialising the FarmName property on Site fixes this as well.

 

[Aaron]

Any update on this ?

[Ves]

Hi Aaron,

I can confirm that this is a bug in the control. We will aim to fix it for one of the upcoming builds. I am afraid there's no other workaround than using non-null values at the moment.

I have updated your Telerik points.


Best regards,
Ves
Telerik by Progress

[Namek]

Same for me at *2017.2.0614.234*.

[Stefan Nenchev]

Hello Namek, Aaron,

Indeed, we have applied a fix for Xamarin.Android, however, the issue can still be reproduced in a Xamarin.Forms approach. Actually, the issue affects iOS and UWP as well so we have logged a task of unifying the behavior for all platforms.

As for the actual issue, you are experiencing, I have attached a sample with a workaround which you can apply at your end. Please have a look at the custom renderer where the CreateAdapter method is overridden so it returns a custom RadListViewDataSourceAdapter. Eventually, you can choose the name of the group where the null items will be located:

public override void OnBindGroupHolder(ListViewHolder holder, object item)
       {
           XF.BindableObject cell = this.GetHeaderCell(holder, item);

           if (cell != null)
           {
               if (cell.BindingContext != item)
               {
                   cell.BindingContext = item;
               }
           }
           else if (holder is ListViewTextHolder)
           {
               if (item == null)
               {
                   item = "Choose";
               }
               ((ListViewTextHolder)holder).TextView.Text = item.ToString();
           }
       }

Regards,
Stefan Nenchev
Progress Telerik

[Namek]

@Stefan Nenchev do you have such workaround for iOS also?

[Stefan Nenchev]

Hi Namek,

Unfortunately, using the same approach is not that straightforward in iOS as the logic is internally handled in the native control. 

However, there is a much easier approach for achieving the behavior in iOS and Android which suggests using a DelegateGroupDescriptor instead of PropertyGroupDescriptor. Here is the change you can apply in the sample project:

lv.GroupDescriptors.Add(new DelegateGroupDescriptor() { KeyExtractor = (s) => ((DataItem)s).Name ?? "[null]" });

I hope it will be useful.

Regards,
Stefan Nenchev
Progress Telerik

[Namysław]

Btw - exact same issue, with **SortDescriptors** and **PropertySortDescriptor** - nullable properties gives me same exception.

[Stefan Nenchev]

Hello Namek,

Analogically to the DelegateGroupDescriptor, you can use the DelegateSortDescriptor and DelegateFilterDescriptor for the other data operations:

lv.SortDescriptors.Add(new DelegateSortDescriptor() { Comparer = (a, b) => (a as DataItem).Name.CompareTo((b as DataItem).Name), SortOrder = SortOrder.Ascending });
lv.FilterDescriptors.Add(new DelegateFilterDescriptor() { Filter = (s) => FilteringMethod(s as DataItem)});

private bool FilteringMethod(DataItem dataItem)
        {
            if (dataItem.Name != null)
            {
                if (dataItem.Name == "Name 1")
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
            return false;
}

We will consider handling the scenario when using the different property descriptors.

Regards,
Stefan Nenchev
Progress Telerik

[Namysław]

I've already found similar workaround for that:


List?.SortDescriptors?.Add(new DelegateSortDescriptor { Comparer = (o, o1) => Nullable.Compare(((MyObject)o).NullableDateProperty, ((MyObject)o1).NullableDateProperty), SortOrder = SortOrder.Descending });