The "Scrolled" event is such a essential feature.
For example, i made a floating searchbar with transparent frame, and a RadListView with HeaderTemplate that is longer than a screen of the device, i would like to detect whether the listview has scrolled for more than 10px vertically. If yes, set the background of the frame of the searchbar to my desired color.Xamarin.Forms, collectionview, listview, and scrollview has Scrolled event, but why RadListView does not? Using ItemAppearing event is just avoiding the problem instead of solving it. It will not be able to fulfill the criteria as the any item does not even enter the screen yet before the required task need to be done.
We have yet to upgrade our mobile app to Xamarin Forms 4.x and the latest Telerik releases due to a hard crash in Android when we leave a page containing a Telerik ListView control.
The exception seems to mirror what is discussed here: https://www.telerik.com/forums/null-ref-error-iorderedtraversalcontroller-updatetraversalorder
Here is what we are seeing... what is the latest on addressing this error? We need to upgrade from Xamarin Forms 3.6.x soon.
10-16 15:00:06.082 I/MonoDroid( 4686): UNHANDLED EXCEPTION:
10-16 15:00:06.084 I/MonoDroid( 4686): System.NullReferenceException: Object reference not set to an instance of an object.
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.PageRenderer.Xamarin.Forms.Platform.Android.IOrderedTraversalController.UpdateTraversalOrder () [0x000a4] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\PageRenderer.cs:186
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].UpdateParentPageTraversalOrder () [0x00025] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:402
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00116] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:366
10-16 15:00:06.084 I/MonoDroid( 4686): at (wrapper delegate-invoke) <Module>.invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:211
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:359
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Element.set_Parent (Xamarin.Forms.Element value) [0x000e9] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:216
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:341
10-16 15:00:06.084 I/MonoDroid( 4686): at Xamarin.Forms.ViewCell.set_View (Xamarin.Forms.View value) [0x00019] in D:\a\1\s\Xamarin.Forms.Core\Cells\ViewCell.cs:25
10-16 15:00:06.084 I/MonoDroid( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.ListView.CellContainerBase.Dispose (System.Boolean disposing) [0x00034] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.084 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.084 I/MonoDroid( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.FormsListViewDataSourceAdapterBase.ClearCachedViews () [0x00023] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.RadListViewDataSourceAdapter.ClearCachedViews () [0x00000] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.RadListViewDataSourceAdapter.Dispose (System.Boolean disposing) [0x00003] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewRenderer.OnElementDetached (Telerik.XamarinForms.DataControls.RadListView oldElement) [0x00042] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Telerik.XamarinForms.Common.Android.AndroidRendererBase`2[S,T].Dispose (System.Boolean disposing) [0x0001f] in <14fbe24a55144e3caaf308ca594f4d5e>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.Platform+DefaultRenderer.Dispose (System.Boolean disposing) [0x0000a] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:1290
10-16 15:00:06.085 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.Platform+DefaultRenderer.Dispose (System.Boolean disposing) [0x0000a] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:1290
10-16 15:00:06.085 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.PageRenderer.Dispose (System.Boolean disposing) [0x00024] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\PageRenderer.cs:53
10-16 15:00:06.085 I/MonoDroid( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at Xamarin.Forms.Platform.Android.AppCompat.FragmentContainer.OnDestroyView () [0x0003c] in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\FragmentContainer.cs:80
10-16 15:00:06.085 I/MonoDroid( 4686): at Android.Support.V4.App.Fragment.n_OnDestroyView (System.IntPtr jnienv, System.IntPtr native__this) [0x00008] in <fefee6c2c695459088a9df092723e052>:0
10-16 15:00:06.085 I/MonoDroid( 4686): at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.97(intptr,intptr)
10-16 15:00:06.088 E/AppCenterCrashes( 4686): Unhandled Exception from source=AndroidEnvironment
10-16 15:00:06.088 E/AppCenterCrashes( 4686): System.NullReferenceException: Object reference not set to an instance of an object.
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.PageRenderer.Xamarin.Forms.Platform.Android.IOrderedTraversalController.UpdateTraversalOrder () [0x000a4] in D:\a\1\s\Xamarin.Forms.Platform.Android\Renderers\PageRenderer.cs:186
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].UpdateParentPageTraversalOrder () [0x00025] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:402
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].OnElementPropertyChanged (System.Object sender, System.ComponentModel.PropertyChangedEventArgs e) [0x00116] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:366
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at (wrapper delegate-invoke) <Module>.invoke_void_object_PropertyChangedEventArgs(object,System.ComponentModel.PropertyChangedEventArgs)
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.BindableObject.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:211
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Element.OnPropertyChanged (System.String propertyName) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:359
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Element.set_Parent (Xamarin.Forms.Element value) [0x000e9] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:216
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:341
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.ViewCell.set_View (Xamarin.Forms.View value) [0x00019] in D:\a\1\s\Xamarin.Forms.Core\Cells\ViewCell.cs:25
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.ListView.CellContainerBase.Dispose (System.Boolean disposing) [0x00034] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.FormsListViewDataSourceAdapterBase.ClearCachedViews () [0x00023] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.RadListViewDataSourceAdapter.ClearCachedViews () [0x00000] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.RadListViewDataSourceAdapter.Dispose (System.Boolean disposing) [0x00003] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.DataControlsRenderer.Android.ListViewRenderer.OnElementDetached (Telerik.XamarinForms.DataControls.RadListView oldElement) [0x00042] in <12ab8aad1d0a41af83f0de07840de122>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Telerik.XamarinForms.Common.Android.AndroidRendererBase`2[S,T].Dispose (System.Boolean disposing) [0x0001f] in <14fbe24a55144e3caaf308ca594f4d5e>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.Platform+DefaultRenderer.Dispose (System.Boolean disposing) [0x0000a] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:1290
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.Platform+DefaultRenderer.Dispose (System.Boolean disposing) [0x0000a] in D:\a\1\s\Xamarin.Forms.Platform.Android\Platform.cs:1290
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Java.Lang.Object.Dispose () [0x00000] in <11a340ccc8de43f09c97400139266ef5>:0
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x000c7] in D:\a\1\s\Xamarin.Forms.Platform.Android\VisualElementRenderer.cs:311
10-16 15:00:06.088 E/AppCenterCrashes( 4686): at Xamarin.Forms.Platform.Android.PageRenderer.Dispose (System.Boolean disposing) [0x00024] in D:\a\1\s\Xamarin.Forms.Platform.Android\
Hello,
Another important control is missing from your Control Suit. That is Rich Text Box control, same like one available from SyncFusion: https://www.syncfusion.com/xamarin-ui-controls/xamarin-richtexteditor
Please give us a rich text editor control like that. Thank you.
Do you have plans to develop controls for the UNO platform?
There are other companies that have already stated that they are working on it, for example,
https://www.syncfusion.com/blogs/post/collaboration-syncfusion-uno-platform.aspx
Hi Team,
I implemented radcheckbox in my xamarin telerik application. In which i select checkbox and afterword i post some data through webAPI. After completion of posting data i got response from server and my app got crashed and show me following stack trace data,
at Telerik.XamarinForms.PrimitivesRenderer.iOS.CheckBoxRenderer.OnElementDetached (Telerik.XamarinForms.Primitives.RadCheckBox oldElement) [0x00025] in <f3723b4c1d3f406496717d69142c8f84>:0
at Telerik.XamarinForms.Common.iOS.IosRendererBase`2[S,T].Dispose (System.Boolean disposing) [0x0001f] in <81c15264f2164ef79a02e84ed79e8bfd>:0
at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:147
at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose (System.Boolean disposing) [0x0003f] in <612eab01c6f546df983c0637f996b4cd>:0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.Dispose () [0x00000] in <612eab01c6f546df983c0637f996b4cd>:0
at Xamarin.Forms.Platform.iOS.VisualElementRenderer`1[TElement].Dispose (System.Boolean disposing) [0x00058] in <612eab01c6f546df983c0637f996b4cd>:0
at Foundation.NSObject.Dispose () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.14.0.114/src/Xamarin.iOS/Foundation/NSObject2.cs:147
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildRemoved (Xamarin.Forms.VisualElement view) [0x0003e] in <612eab01c6f546df983c0637f996b4cd>:0
at Xamarin.Forms.Platform.iOS.VisualElementPackager.OnChildRemoved (System.Object sender, Xamarin.Forms.ElementEventArgs e) [0x0000f] in <612eab01c6f546df983c0637f996b4cd>:0
at Xamarin.Forms.Element.OnChildRemoved (Xamarin.Forms.Element child) [0x00007] in D:\a\1\s\Xamarin.Forms.Core\Element.cs:343
at Xamarin.Forms.VisualElement.OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:750
at Xamarin.Forms.Layout`1[T].OnChildRemoved (Xamarin.Forms.Element child) [0x00000] in <4542de7f0f544d51b46d63bd15d5f6b5>:0
at Xamarin.Forms.Layout.OnInternalRemoved (Xamarin.Forms.View view) [0x00012] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:464
at Xamarin.Forms.Layout.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x0002b] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:427
at (wrapper delegate-invoke) <Module>.invoke_void_object_NotifyCollectionChangedEventArgs(object,System.Collections.Specialized.NotifyCollectionChangedEventArgs)
at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00018] in <a1ab7fc4639d4d84af41d68234158b1c>:0
at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object item, System.Int32 index) [0x00009] in <a1ab7fc4639d4d84af41d68234158b1c>:0
at System.Collections.ObjectModel.ObservableCollection`1[T].RemoveItem (System.Int32 index) [0x00021] in <a1ab7fc4639d4d84af41d68234158b1c>:0
at System.Collections.ObjectModel.Collection`1[T].Remove (T item) [0x00027] in <939d99b14d934342858948926287beba>:0
at Xamarin.Forms.Layout.OnInternalAdded (Xamarin.Forms.View view) [0x0000b] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:451
at Xamarin.Forms.Layout.InternalChildrenOnCollectionChanged (System.Object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00078] in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:443
at (wrapper delegate-invoke) <Module>.invoke_void_object_NotifyCollectionChangedEventArgs(object,System.Collections.Specialized.NotifyCollectionChangedEventArgs)
at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedEventArgs e) [0x00018] in <a1ab7fc4639d4d84af41d68234158b1c>:0
at System.Collections.ObjectModel.ObservableCollection`1[T].OnCollectionChanged (System.Collections.Specialized.NotifyCollectionChangedAction action, System.Object item, System.Int32 index) [0x00009] in <a1ab7fc4639d4d84af41d68234158b1c>:0
My xaml code,
<telerikControls:RadCheckBox IsChecked="{Binding IsSelected, Mode=TwoWay}" HorizontalOptions="Center" VerticalOptions="Center" />
My model class code,
private bool _isSelected;
public bool IsSelected
{
get { return _isSelected; }
set
{
_isSelected = value;
}
}
Version information,
Xmarin form version : 4.1.0
Telerik UI version : 2019.2.802.1
iOS version 12.2
If we have a ListView with a CheckBox inside the ItemTemplate and the whole ListView is placed in a Popup control, following the next steps:
1. Open the popup
2. Check and uncheck the CheckBox control in any of the items.
3. Click into the popup and then outside to close it.
NullReferenceException is raised on iOS.
It would be a good to have function to be able to swipe on the header and also to be able to swipe on the content area to go to next tab.
This request is for iOS and Android
I would like to extend my XF project to Windows Presentation Framework (WPF) and MacOs when possible, both now supported by XF.
Request is that Telerik begin to include some work in these areas in its near-future roadmaps.
UPDATE:
The issue is confirmed to be in Xamarin.Forms framework. A fix is already provided. The Xamarin.Forms 4.3 version will contain the fix.
Hello Team,
Currently we are working with Telerik xamarin forms application,We are using radlistview.I want to scroll and select item with up and down arrow keys.Can we have any sample on this.
Thanks & regards
Uday raj
the following exceptions occur when upgrading to Xamarin.Forms v 4.0:
System.NotSupportedException: Unable to activate instance of type Telerik.XamarinForms.DataControlsRenderer.Android.ListView.TemplateCellContainer
System.NullReferenceException: Object reference not set to an instance of an object
at Telerik.XamarinForms.InputRenderer.iOS.SegmentedControlRenderer.OnElementDetached
Add support fir VisualElement.AccessKey like in the Xamarin.Forms controls: