I'm getting an exception on a Xamarin Forms content page with Xaml, on the initializecomponent method. The exception occurs on the generated xaml.gs page. I haven't changed any code form a working version. Maybe something upstream has changed. The exception message is ""
Value cannot be null.
Parameter name: binding
stack trace:
at Xamarin.Forms.BindableObject.SetBinding (Xamarin.Forms.BindableProperty targetProperty, Xamarin.Forms.BindingBase binding, System.Boolean fromStyle) [0x00011] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:293
at Xamarin.Forms.BindableObject.SetBinding (Xamarin.Forms.BindableProperty targetProperty, Xamarin.Forms.BindingBase binding) [0x00000] in D:\a\1\s\Xamarin.Forms.Core\BindableObject.cs:117
at ....LoginPage.InitializeComponent () [0x00045] in ...\obj\Debug\netstandard2.0\Views\Navigation\Login.xaml.g.cs:34
at FieldServices.LoginPage..ctor () [0x0002b] in ..\Views\Navigation\Login.xaml.cs:25
where occurrs:
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Xamarin.Forms.Build.Tasks.XamlG", "0.0.0.0")]
private void InitializeComponent() {
global::Xamarin.Forms.Xaml.Extensions.LoadFromXaml(this, typeof(LoginPage));
email = global::Xamarin.Forms.NameScopeExtensions.FindByName(this, "email");
password = global::Xamarin.Forms.NameScopeExtensions.FindByName(this, "password");
loginButton = global::Xamarin.Forms.NameScopeExtensions.FindByName(this, "loginButton");
}
I rarely get this error when pulling code down. First, double-check that your code is fine. In this case, I would make sure all the bindings are named correctly with no typos.
In the event that you cannot find an error and are thoroughly convinced there is nothing wrong with the code, try steps like
Clean and Rebuild
Close your Visual Studio and restart it
Hopefully the error is solved as easy as this.
On top of cleaning and rebuilding, manually delete all the obj and bin folders from your solution directory. Those xaml.gs files are generated files and sometimes they seem to not regenerate when they should.
I'm getting an exception on a Xamarin Forms content page with Xaml, on the initializecomponent method. The exception occurs on the generated xaml.gs page. I haven't changed any code form a working version. Maybe something upstream has changed.
It is not reproduceable by myside, but per experience there are a few things you can try:
Put your project in a short path like "C:\".
Try a new blank project, see if the error occors.
If none of the above works, you can try reinstalling Xamarin in your VS.
This was solved due to my not linking a static resource that was declared in the xaml
Related
I am trying to make my Xamarin Project use MVVM with Prism and DryIoc.
I mostly want to use AutoRegistration like below:
[AutoRegisterForNavigation]
...
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
//Pages
containerRegistry.RegisterForNavigation<NavigationPage>();
//Services
containerRegistry.RegisterSingleton<ILocalDatabase, LocalDatabase>();
containerRegistry.RegisterSingleton<IUserProfileDataStore, UserProfileDataStore>();
containerRegistry.RegisterSingleton<IApplicationSettings, ApplicationSettings>();
containerRegistry.RegisterSingleton<ILogger, Logger>();
containerRegistry.RegisterSingleton<IApiService, ApiService>();
containerRegistry.RegisterSingleton<IUserSession, UserSession>();
containerRegistry.Register<IBrowser, BrowserImplementation>();
containerRegistry.Register<IConnectivity, ConnectivityImplementation();
containerRegistry.Register<IFileSystem, FileSystemImplementation>();
containerRegistry.Register<ICoreServices, CoreServices>();
}
I have also tried Manual Registration:
containerRegistry.RegisterForNavigation<LoginPage, LoginPageViewModel>();
Neither works, It hits the Login Page code behind then breaks with the following error:
Exception - High: Prism.Ioc.ContainerResolutionException:
An unexpected error occurred while resolving 'AppetiteApp.ViewModels.LoginPageViewModel' --->
DryIoc.ContainerException: code: UnableToResolveUnknownService; message: Unable to resolve
Resolution root AppetiteApp.ViewModels.LoginPageViewModel
with passed arguments [value(Prism.Navigation.ErrorReportingNavigationService)]
**System.NullReferenceException:** 'Object reference not set to an instance of an object.'
I've also tried using a Linker file setting it's build action to "linkdescription"
As for my Login Page here is the declaration
public LoginPageViewModel(ICoreServices coreServices)
: base(coreServices)
The constructor of LoginPageViewModel requires the ICoreServices argument which is registered.
The error message says that the LoginPageViewModel itself is unknown to the IoC - it means the type LoginPageViewModel is not directly registered and not found through dynamic registrations or unknown service resolvers.
I am not a user of the Xamarin Prism so I am not sure about its mechanism for registering the view models.
Btw, this part of error
Resolution root AppetiteApp.ViewModels.LoginPageViewModel
with passed arguments [value(Prism.Navigation.ErrorReportingNavigationService)]
basically means the view-model was resolved via the foollowing call resolver.Resolve(typeof(LoginPageViewModel), args: new[] { errorReportingNavigationService })
Hope it will help you or someone knowledgeable in Xamarin to track the error cause.
So Once I investigated Inside of ICoreServices I commented out each of the dependencies then discovered that IUserSession was the once causing problems then I dug into that and discovered that the dependences for IAppInfo and IVersionTracking were missing in the App.Xaml.cs registr tyepes so I added that and then it worked!
containerRegistry.Register<IAppInfo, AppInfoImplementation>();
containerRegistry.Register<IVersionTracking, VersionTrackingImplementation>();
It looks like Vuepress is made for public docs, but we decided to add client and server security to protect some of the doc pages. But unfortunately although oidc-client (https://github.com/IdentityModel/oidc-client-js/wiki) works during dev, it throws exception when build.
I get ReferenceError: window is not defined and when I try to trick the compiler with const window = window || { location: {} }; I get TypeError: Cannot read property 'getItem' of undefined
Any idea how to make this work?
This was driving me nuts also. I discovered the component I was trying to add was looking at window.location in its code - this was triggering the error.
My understanding is that the build process has not access to Browser things like window etc.
As soon as I removed the window.location bit from my code things built just fine and all is well.
I am building an iOS app with Xamarin and MvvmCross the required the use of Bluetooth LE. I am trying to use this plugin:
https://github.com/aritchie/bluetoothle
Here is my code:
var server = CrossBleAdapter.Current.CreateGattServer();
await server.Start(new AdvertisementData()); // throws exception
It throws an exception when trying to start the server:
{System.ArgumentException: Invalid State - Unknown at
Plugin.BluetoothLE.Server.GattServer.Start
(Plugin.BluetoothLE.Server.AdvertisementData adData) [0x0005f] in
<4281c4bd57f24525b20baae1afdf610b>:0
Apparently this plugin is easy to use so I must be missing something obvious?
That Exception indicates that the hardware is in invalid or initializing state and can be seen here: https://github.com/aritchie/bluetoothle/blob/master/Plugin.BluetoothLE.Apple.Shared/Server/GattServer.cs#L74
if (this.manager.State != CBPeripheralManagerState.PoweredOn)
throw new ArgumentException("Invalid State - " + this.manager.State);
I believe this is a bug in the code as it does not wait for the delegate to signal that the State has changed.
I found a solution. Instead of placing the code in my Core project, I placed it inside the iOS project itself, in a ViewDidAppear function, and placed a global variable in my UIViewController class:
private IGattServer server = CrossBleAdapter.Current.CreateGattServer();
I think you need to access the adapter with the appropriate thread, or at the appropriate time (after other initialization), hence why it was crashing before. I couldn't find an appropriate place to put this in my Core project, so I'm not sure if I have to put this code in each platform. Anyhow here's a solution for anyone else with this problem.
I am trying to reduce app size and enabled "Link All Assemblies", but my app crashes with following error
MvvmCross.Platform.Exceptions.MvxException: Failed to construct and initialize ViewModel for type Japam.Core.ViewModels.MantraasViewModel from locator MvxDefaultViewModelLocator - check InnerException for more information
I tried
--linkskip=mvvmcross.platform.ios
--linkskip=mvvmcross.core
--linkskip=mvvmcross.platform
but no luck, kept preserve attribute at assembly level of my core pcl project.
Also added a couple of more methods in LinkerPleaseIncludefile
public void Include(MvvmCross.Platform.IoC.MvxPropertyInjection injection)
{
injection = new MvvmCross.Platform.IoC.MvxPropertyInjection();
}
public void Include(MvxDefaultViewModelLocator locator)
{
locator = new MvxDefaultViewModelLocator();
}
but no use, could somebody help me find out what is missing
MvvmCross.Platform.Exceptions.MvxException: Failed to construct and initialize ViewModel for type
Japam.Core.ViewModels.MantraasViewModel from locator
MvxDefaultViewModelLocator - check InnerException for more information
---> MvvmCross.Platform.Exceptions.MvxException: Problem creating viewModel of type MantraasViewModel --->
MvvmCross.Platform.Exceptions.MvxIoCResolveException: Failed to
construct MantraasViewModel --->
System.Reflection.TargetInvocationException: Exception has been thrown
by the target of an invocation. --->
MvvmCross.Platform.Exceptions.MvxIoCResolveException: Failed to
resolve parameter for parameter sqliteConnectionFactory of type
IMvxSqliteConnectionFactory when creating
Japam.Core.Services.DataServices.MantraService
at MvvmCross.Platform.IoC.MvxSimpleIoCContainer.GetIoCParameterValues
(System.Type type, System.Reflection.ConstructorInfo firstConstructor)
[0x00036] in D:\git\MvvmCross\MvvmCross\Platform\Platform\IoC\
Finally I found the issue, it's SQLite problem so I added below three commands and it started working hope this helps someone else
--linkskip=MvvmCross.Plugins.Sqlite
--linkskip=SQLite-net
--linkskip=MvvmCross.Plugins.Sqlite.iOS
I should kept SQLite earlier it self my last project I did kept SQLite but forgot this time
I'm trying to adjust my WP8 project from self made MVVM implementation to MVVM Light.
The application compiles without errors, but when I open my MainPage.xaml in Expression Blend, I will get this error:
Class project.Services.INavigationService is already registered. App.xaml
My ViewModelLocator.cs:
/// <summary>
/// Initializes a new instance of the ViewModelLocator class.
/// </summary>
public ViewModelLocator()
{
ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
if (ViewModelBase.IsInDesignModeStatic)
{
}
else
{
if (!SimpleIoc.Default.IsRegistered<INavigationService>())
{
SimpleIoc.Default.Register<INavigationService>(() => new NavigationService());
}
}
SimpleIoc.Default.Register<MainPage>();
SimpleIoc.Default.Register<SettingsEditViewModel>();
}
As you can see from my code comment, I've already tried the fix supposed here, but I'm still getting this error in Blend. There is no other place left where I could register the INavigationService, so what could be the problem?
Any ideas? :)
I had the same issue, and this seems to be a Visual Studio issue in combination with XAML-Designer, Static Factories/Locators and Design-Time creation of objects. However: The solutions were the following:
Register without a factory (not recommended)
SimpleIoc.Default.Register<INavigationService>();
Or if you want to use a factory, unregister before registering the factory
SimpleIoc.Default.Unregister<INavigationService>();
SimpleIoc.Default.Register<INavigationService>(() => new NavigationService());
Prevent the ViewModelLocator from being created more than once by the designer/Blend by making the constructor static
static ViewModelLocator() { ... }
The error is cumbersome but could happen in this scenario: You create objects during design-time (the ViewModelLocator within App.xaml probably) and whenever you change something in your Code, the Compiler is triggered and the ViewModelLocator gets re-created without ever unregistering the services. Therefore it will complain that in the factory has already been registered. In theory, when registering classes without factories multiple times, there should be an error as-well.
Might already be solved by now, but I think you can just solve the issue in your example case by not using the factory method override.
SimpleIoc.Default.Register<INavigationService, NavigationService>();
If you do need a factory method, then you can mix this line in with your factory method approach using the design mode check like you have been.
if (ViewModelBase.IsInDesignModeStatic)
{
SimpleIoc.Default.Register<INavigationService, NavigationService>();
}
else
{
SimpleIoc.Default.Register<INavigationService>(CreateNavigationService);
}
This seems like a super old question, but after hours of googling, this is the only question that's similar to my problem, so answering here for other people.
Make sure that you have IsDataSource on your ViewModelLocator:
<vm:ViewModelLocator x:Key="Locator" d:IsDataSource="True" />
That solved my problem and my design data popped up straightaway.
Weirdly, after putting that on, all my "INavigationService is already registered" errors goes away!
Not sure why, but I only get this error when my xaml designer window is open. When I compile with it closed, the error goes away and the project is built and runs successfully.