Develop Reference

When start in dark mode, get NullReferenceException in PlatformConfigurationExtensions.cs

By default in my xamarin forms app I have
AppCompatDelegate.DefaultNightMode =AppCompatDelegate.ModeNightNo;
But when I start it in dark mode I get the following exception
enter image description here,
in Xamarin.Forms.Platform.Android\PlatformConfigurationExtensions.cs
System.NullReferenceException:'Object reference not set to an instance of an object.'
Stacktrace:
at Xamarin.Forms.Platform.Android.PlatformConfigurationExtensions.OnThisPlatform[T] (T element) [0x00000]
in D:\a\1\s\Xamarin.Forms.Platform.Android\PlatformConfigurationExtensions.cs:8
at Xamarin.Forms.Platform.Android.AppCompat.FragmentContainer.OnResume () [0x00007]
in D:\a\1\s\Xamarin.Forms.Platform.Android\AppCompat\FragmentContainer.cs:126
at AndroidX.Fragment.App.Fragment.n_OnResume (System.IntPtr jnienv, System.IntPtr native__this) [0x00008]
in D:\a\1\s\generated\androidx.fragment.fragment\obj\Release\monoandroid9.0\generated\src\AndroidX.Fragment.App.Fragment.cs:2548
at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.115(intptr,intptr)
It only happens in dark mode, in light mode it init normally.
I was trying to debug but all the threads at that moment are executing external code

Consuming WCF service in Xamarin Forms

I am wishing to connect to a WCF service (running on a Windows PC) via Xamarin Form based on this sample code.
I successfully managed to find and create the Connected Service pointing to the WCF. and I followed the same approach that I earlier used in the UWP environment.
But once I call any of the methods exposed in the service I get this exception in the Android environment.
The method or operation is not implemented
I don't use PCL style but .net way.
here is the stack trace of the exception.
at System.ServiceModel.Channels.BindingContext.BuildInnerChannelFactory[TChannel] () [0x00007] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BindingContext.cs:149
at System.ServiceModel.Channels.BindingElement.BuildChannelFactory[TChannel] (System.ServiceModel.Channels.BindingContext context) [0x0000e] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BindingElement.cs:52
at System.ServiceModel.Channels.BinaryMessageEncodingBindingElement.BuildChannelFactory[TChannel] (System.ServiceModel.Channels.BindingContext context) [0x0000e] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BinaryMessageEncodingBindingElement.cs:94
at System.ServiceModel.Channels.BindingContext.BuildInnerChannelFactory[TChannel] () [0x00007] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/BindingContext.cs:149
at System.ServiceModel.Channels.Binding.BuildChannelFactory[TChannel] (System.ServiceModel.Channels.BindingParameterCollection parameters) [0x0000e] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/Binding.cs:133
at System.ServiceModel.ChannelFactory.CreateFactory () [0x000be] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ChannelFactory.cs:202
at System.ServiceModel.ChannelFactory.OnOpening () [0x00006] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ChannelFactory.cs:383
at System.ServiceModel.Channels.CommunicationObject.ProcessOpening () [0x00017] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/CommunicationObject.cs:276
at System.ServiceModel.Channels.CommunicationObject.Open (System.TimeSpan timeout) [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/CommunicationObject.cs:169
at System.ServiceModel.Channels.CommunicationObject.Open () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel.Channels/CommunicationObject.cs:164
at System.ServiceModel.ChannelFactory.EnsureOpened () [0x0004c] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ChannelFactory.cs:297
at System.ServiceModel.ChannelFactory`1[TChannel].CreateChannel () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ChannelFactory_1.cs:108
at System.ServiceModel.DuplexClientBase`1[TChannel].CreateChannel () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/DuplexClientBase.cs:123
at System.ServiceModel.ClientBase`1[TChannel].get_InnerChannel () [0x00008] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ClientBase.cs:186
at System.ServiceModel.ClientBase`1[TChannel].get_Channel () [0x00000] in /Users/builder/jenkins/workspace/archive-mono/2020-02/android/release/mcs/class/System.ServiceModel/System.ServiceModel/ClientBase.cs:192
at AppMobileService.AppMobileCommandHandlerClientBase.SubscribeAsync (System.String name, AppMobileService.AppMobileConnectionType connectionType) [0x00001] in C:\Users\adm\Desktop\AppMobilePortable\AppMobilePortable\AppMobilePortable\Connected Services\AppMobileService\Reference.cs:945
at PortableAppMobile.Services.AppMobileClientService.Connect () [0x00024] in C:\Users\adm\Desktop\AppMobilePortable\AppMobilePortable\AppMobilePortable\Service\AppMobileClientService.cs:136 ```

Xamarin camera2 api is in background not working

I am interested in Xamarin and I search, how I can take a photo from camera without device's native camera application. And I found Camera2 API, then I search sample app and I found this sample app: https://learn.microsoft.com/en-us/samples/xamarin/monodroid-samples/android50-camera2basic/
It worked very well when I tried it in the foreground but it gives an error when I put it in the background.
How can I get it running in the background?
Camera2BasicFragment.cs codes: https://paste.ubuntu.com/p/CqDkyMx8qW/
Exceptions:
Exception image 1
Exception image 2
Exception Text:
{Java.Lang.IllegalStateException: CameraDevice was already closed at Java.Interop.JniEnvironment+InstanceMethods.CallIntMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x0006e] in <dac4c5a4b77f4e61a5e6d9d3050dfb9f>:0 at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeAbstractInt32Method (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x00014] in <dac4c5a4b77f4e61a5e6d9d3050dfb9f>:0 at Android.Hardware.Camera2.CameraCaptureSessionInvoker.Capture (Android.Hardware.Camera2.CaptureRequest request, Android.Hardware.Camera2.CameraCaptureSession+CaptureCallback listener, Android.OS.Handler handler) [0x0006e] in /Users/builder/azdo/_work/204/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-27/mcw/Android.Hardware.Camera2.CameraCaptureSession.cs:969 at Camera2Basic.Camera2BasicFragment.LockFocus () [0x00020] in C:\Users\Harun\Desktop\x\Camera2Basic\Camera2BasicFragment.cs:576 at Camera2Basic.Camera2BasicFragment.TakePicture () [0x00001] in C:\Users\Harun\Desktop\x\Camera2Basic\Camera2BasicFragment.cs:563 at Camera2Basic.Camera2BasicFragment.OnClick (Android.Views.View v) [0x00013] in C:\Users\Harun\Desktop\x\Camera2Basic\Camera2BasicFragment.cs:676 at Android.Views.View+IOnClickListenerInvoker.n_OnClick_Landroid_view_View_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_v) [0x00010] in /Users/builder/azdo/_work/204/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-27/mcw/Android.Views.View.cs:2176 at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.19(intptr,intptr,intptr) --- End of managed Java.Lang.IllegalStateException stack trace ---java.lang.IllegalStateException: CameraDevice was already closed at android.hardware.camera2.impl.CameraDeviceImpl.checkIfCameraClosedOrInError(CameraDeviceImpl.java:1997) at android.hardware.camera2.impl.CameraDeviceImpl.submitCaptureRequest(CameraDeviceImpl.java:844) at android.hardware.camera2.impl.CameraDeviceImpl.capture(CameraDeviceImpl.java:741) at android.hardware.camera2.impl.CameraCaptureSessionImpl.capture(CameraCaptureSessionImpl.java:179) at crc64b678081366886b9e.Camera2BasicFragment.n_onClick(Native Method) at crc64b678081366886b9e.Camera2BasicFragment.onClick(Camera2BasicFragment.java:77) at android.view.View.performClick(View.java:5721) at android.widget.TextView.performClick(TextView.java:10936) at mono.java.lang.RunnableImplementor.n_run(Native Method) at mono.java.lang.RunnableImplementor.run(RunnableImplementor.java:30) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:7406) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)}

Xamarin Forms Android Store crashes when i download the app, debugs perfectly on phone from VS

This is my first commit on google play store. I am using Xamarin Forms and when i run my app localy on my android phone, i have no issues.
When I Archive and Distribute the App within VS using Archive Manager and download it on my phone, or any other android phone, the App crashes before going to the 1st screen.
Under Play Console I can see the following error on the Pre-Lunch report
Blockquote
FATAL EXCEPTION: main
Process: com.*****.*****, PID: 8647
android.runtime.JavaProxyThrowable: Xamarin.Forms.Xaml.XamlParseException: Position 30:125. No method OnMenuItemSelected2 found on type *****.Menus.MainPageV2
at Xamarin.Forms.Xaml.ApplyPropertiesVisitor.SetPropertyValue (System.Object xamlelement, Xamarin.Forms.Xaml.XmlName propertyName, System.Object value, System.Object rootElement, Xamarin.Forms.Xaml.INode node, Xamarin.Forms.Xaml.HydrationContext context, System.Xml.IXmlLineInfo lineInfo) [0x000ee] in :0
at Xamarin.Forms.Xaml.ApplyPropertiesVisitor.Visit (Xamarin.Forms.Xaml.ValueNode node, Xamarin.Forms.Xaml.INode parentNode) [0x00072] in :0
at Xamarin.Forms.Xaml.ValueNode.Accept (Xamarin.Forms.Xaml.IXamlNodeVisitor visitor, Xamarin.Forms.Xaml.INode parentNode) [0x00000] in :0
at Xamarin.Forms.Xaml.ElementNode.Accept (Xamarin.Forms.Xaml.IXamlNodeVisitor visitor, Xamarin.Forms.Xaml.INode parentNode) [0x00043] in :0
at Xamarin.Forms.Xaml.ElementNode.Accept (Xamarin.Forms.Xaml.IXamlNodeVisitor visitor, Xamarin.Forms.Xaml.INode parentNode) [0x00078] in :0
at Xamarin.Forms.Xaml.ElementNode.Accept (Xamarin.Forms.Xaml.IXamlNodeVisitor visitor, Xamarin.Forms.Xaml.INode parentNode) [0x00078] in :0
at Xamarin.Forms.Xaml.RootNode.Accept (Xamarin.Forms.Xaml.IXamlNodeVisitor visitor, Xamarin.Forms.Xaml.INode parentNode) [0x00043] in :0
at Xamarin.Forms.Xaml.XamlLoader.Visit (Xamarin.Forms.Xaml.RootNode rootnode, Xamarin.Forms.Xaml.HydrationContext visitorContext) [0x00083] in :0
at Xamarin.Forms.Xaml.XamlLoader.Load (System.Object view, System.String xaml) [0x0008f] in :0
at Xamarin.Forms.Xaml.XamlLoader.Load (System.Object view, System.Type callingType) [0x0002f] in :0
at Xamarin.Forms.Xaml.Extensions.LoadFromXaml[TXaml] (TXaml view, System.Type callingType) [0x00000] in :0
at ****.Menus.MainPageV2.InitializeComponent () [0x00000] in :0
at ****.Menus.MainPageV2..ctor () [0x00006] in :0
at ****.App..ctor () [0x0000c] in :0
at ****.Droid.MainActivity.OnCreate (Android.OS.Bundle bundle) [0x00022] in :0
at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in :0
at (wrapper dynamic-method) System.Object:efb18139-d766-47ea-a9bd-57beaf3952f0 (intptr,intptr,intptr)
at md5684c7b5241d0a7c4d4ea0533a804cbec.MainActivity.n_onCreate(Native Method)
at md5684c7b5241d0a7c4d4ea0533a804cbec.MainActivity.onCreate(MainActivity.java:29)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
The thing is that my Menus.MainPageV2 includes OnMenuItemSelected2 which is run just fine when testing localy
The automated Google Test results on the on the Pre-Lunch report are failing for all testing devices with the same error.
Things I tried changing, re-Archiving and Distributing:
- Closed VS, cleaned bin, obj directories and Re-Built
- Upgraded to the latest Xamarin Forms Nuget
- Linking with None, Sdk and User Assemblies, Sdk Assemblies only
Anyone have any ideas on what else i might try to get this to work ?
Thank you for your time.

Xamarin.IOS MvvmCross App throws NullReference Exception in ViewDidLoad method in iOS9

I am working on an existing Xamarin iOS application with a PCL and uses MvvmCross for IoC and Databinding. Built on MvvmCross 3.1.1
The App looks like a TabControl App but it is buttons on the MainViewCotnroller giving the Tab feel to it. Views are declared in the Storyboard and in the MainViewController,
PrepareForSegue(UIStoryboardSegue segue, NSObject sender) method
is overridden to load the selected "Tab" View based on the Segue selected - like below
if (segue.Identifier == "FirstSegue")
{
var dest = segue.DestinationViewController as FirstView;
dest.Request = new MvxViewModelRequest<FirstViewModel>(null, null, new MvxRequestedBy());
foreach (UIView v in src.placeHolderView.Subviews)
{
v.RemoveFromSuperview();
}
dest.View.Frame = new CGRect(0f, 0f, w, h);
src.placeHolderView.Add(dest.View);
}
The App runs fine on iPhones with iOS 7.1 till 8.4.
Just before iOS 9 was released I did a test installation for the App on iPhone 6 with iOS 9.1 beta and the App crashed on loading. I retrieved the device logs (below) and analysed that the problem is in the guts of the MvvmCross ViewDidLoad method. I updated the latest SDKs (XCode 7, Xamarin.IOS 9.0) and followed instructions provided by Xamarin and compiled the App again using the latest SDKs same error. Updated the Nuget package reference for MvvmCross to 3.5.1 and still the same issue
The issues is there is a null reference at Line 44 in the 3.5 MvvMCross Source Code in GitHub
Note: This piece of code has not changed since 3.1 at least and 3.5.1 is the latest in the nuget for MvvmCross
Stack Trace below (App Names, Project Names changed for security reasons):
2015-09-21 11:06:26.991 MyApp[1210:60b] Unhandled managed exception:
Object reference not set to an instance of an object (System.NullReferenceException)
at Cirrious.CrossCore.Mvx.Resolve[IMvxViewModelLoader] () [0x00006] in <filename unknown>:0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerExtensionMethods.LoadViewModel (IMvxTouchView touchView) [0x00057] in <filename unknown>:0
at Cirrious.MvvmCross.Views.MvxViewExtensionMethods.OnViewCreate (IMvxView view, System.Func`1 viewModelLoader) [0x00012] in <filename unknown>:0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerExtensionMethods.OnViewCreate (IMvxTouchView touchView) [0x00001] in <filename unknown>:0
at Cirrious.MvvmCross.Touch.Views.MvxViewControllerAdapter.HandleViewDidLoadCalled (System.Object sender, System.EventArgs e) [0x00007] in <filename unknown>:0
at (wrapper delegate-invoke) <Module>:invoke_void_object_EventArgs (object,System.EventArgs)
at Cirrious.CrossCore.Core.MvxDelegateExtensionMethods.Raise (System.EventH
andler eventHandler, System.Object sender) [0x00004] in <filename unknown>:0
at Cirrious.CrossCore.Touch.Views.MvxEventSourceTableViewController.ViewDidLoad () [0x00006] in <filename unknown>:0
at MyProject.Touch.MostPurchasedView.ViewDidLoad () [0x00048] in d:\Working\Repo\MyApp\<MyProjectName>\MyProject.Touch\Views\OneOfTheView.cs:31
at (wrapper managed-to-native) ObjCRuntime.Messaging:IntPtr_objc_msgSendSuper (intptr,intptr)
at UIKit.UIViewController.get_View () [0x00030] in /Users/builder/data/lanes/2077/d230615b/source/maccore/src/build/ios/native/UIKit/UIViewController.g.cs:2632
at MyProject.Touch.HomeViewController.PrepareForSegue (UIKit.UIStoryboardSegue segue, Foundation.NSObject sender) [0x0016a] in d:\Working\Repo\MyApp\MyProject.Mobile\MyProject.Touch\HomeViewController.cs:335
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/2077/d230615b/source/maccore/src/UIKit/UIApplication.cs:74
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0001c] in /Users/builder/data/lanes/2077/d230615b/source/maccore/src/UIKit/UIApplication.cs:57
at MyProject.Touch.Application.Main (System.String[] args) [0x00001] in d:\Working\Repo\MyApp\MyProject.Mobile\MyProject.Touch\Main.cs:16
2015-09-21 11:06:26.994 MyApp[1210:60b] critical: Stacktrace:
Native stacktrace:
.....
I tried the above with just calling the below in the View.cs:
public override void ViewDidLoad()
{
try
{
base.ViewDidLoad();
}
catch (Exception ex)
{
// throw a toast msg in the UI
}
}
I disabled all the base.ViewDidLoad() in all the View.cs files in the ViewDidLoad override methods to take it to the next level and the same problem but inside the constructor of MvxSimpleTableViewSource class
Device Log below:
Object reference not set to an instance of an object (System.NullReferenceException)
at Cirrious.CrossCore.Mvx.TryResolve[IMvxTouchSystem] (IMvxTouchSystem& service) [0x00006] in <filename unknown>:0
at Cirrious.CrossCore.Touch.Platform.MvxIosMajorVersionChecker.ReadIsIosVersionOrHigher (Int32 target, Boolean defaultValue) [0x00000] in <filename unknown>:0
at Cirrious.CrossCore.Touch.Platform.MvxIosMajorVersionChecker..ctor (Int32 major, Boolean defaultValue) [0x00006] in <filename unknown>:0
at Cirrious.MvvmCross.Binding.Touch.Views.MvxSimpleTableViewSource..ctor (UIKit.UITableView tableView, System.String nibName, System.String cellIdentifier, Foundation.NSBundle bundle) [0x00000] in <filename unknown>:0
at MyProject.Touch.MostPurchasedView.ViewDidLoad () [0x00059] in d:\Working\Repo\MyApp\MyProject.Mobile\MyProject.Touch\Views\OneOfTheView.cs:42
at (wrapper managed-to-native) ObjCRuntime.Messaging:IntPtr_objc_msgSendSuper (intptr,intptr)
at UIKit.UIViewController.get_View () [0x00030] in /Users/builder/data/lanes/2077/d230615b/source/maccore/src/build/ios/native/UIKit/UIViewController.g.cs:2632
at MyProject.Touch.HomeViewController.PrepareForSegue (UIKit.UIStoryboardSegue segue, Foundation.NSObject sender) [0x0016a] in d:\Working\Repo\MyApp\MyProject.Mobile\MyProject.Touch\HomeViewController.cs:343
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/2077/d230615b/source/maccore/src/UIKit/UIApplication.cs:74
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0001c] in /Users/builder/data/lanes/2077/d230615b/source/maccore/src/UIKit/UIApplication.cs:57
at MyProject.Touch.Application.Main (System.String[] args) [0x00001] in d:\Working\Repo\MyApp\MyProject.Mobile\MyProject.Touch\Main.cs:16
In short :
Only in iOS 9.1, MvvmCross 3.1.1 AND MvvmCross 3.5.1 has a NullReference Issue in line 44 of the MvxViewControllerExtensionMethods class which gets called during ViewDidLoad but works well with iOS 8.4 and below
I am just getting familiar with MvvmCross framework and unsure whether it is an issue with MvvmCross and iOS 9.
Has anyone come across this issue? Any help on this would be appreciated.
Note: The MvvmCross samples work fine with iOS9. So I believe it has to be something with the Tab implementation.

One thing is that MvvmCross 3.1.1 not is build for iOS unified code. This will prevent you from submitting your app. MvvmCross 4.0 is currently in beta, but i would recommend using it, because it has many fixes.
If the code crashes on line 44 while trying to resolve IMvxViewModelLoader, it probably means that you are missing some package where the IMvxViewModelLoader is.