I am trying to connect my xamarin app with SQLite, everything seems fine but in App.xaml.cs i get the following error: System.NullReferenceException: 'Object reference not set to an instance of an object.'
This is how my App.xaml.cs page looks like:
using System;
using TestAppDemo.Services;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace TestAppDemo
{
public partial class App : Application
{
public App()
{
InitializeComponent();
DependencyService.Get<ISQLite>().GetConnectionWithCreateDatabase();
MainPage = new NavigationPage(new MainPage());
}
protected override void OnStart()
{
}
protected override void OnSleep()
{
}
protected override void OnResume()
{
}
}
}
Can anyone help? Do I need to provide you with more information?
Thanks!
Related
I am trying to create an optimized Event Tracker for my Xamarin.forms prism application. I would like to know whether there is any method to find out when the page load is finished. If someone could help me, please save my time.
You can implement page loading methods for different platforms through custom renderer.
For iOS, override the viewDidLoad method, ViewDidLoad(Called after the controller's view is loaded into memory.)
[assembly:ExportRenderer (typeof(ContentPage), typeof(MyRenderer))]
namespace Demo.iOS
{
public class MyRenderer : PageRenderer
{
protected override void OnElementChanged(VisualElementChangedEventArgs e)
{
base.OnElementChanged(e);
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
}
}
}
For Android, rewrite the OnAttachedToWindow method, OnAttachedToWindow(This is called when the view is attached to a window.)
[assembly: ExportRenderer(typeof(ContentPage), typeof(MyRenderer))]
namespace Demo.Droid
{
public class MyRenderer : PageRenderer
{
public MyPageRenderer(Context context) : base(context)
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Page> e)
{
base.OnElementChanged(e);
}
protected override void OnAttachedToWindow()
{
base.OnAttachedToWindow();
}
}
}
i want to create data to all the application
using static System.Net.Mime.MediaTypeNames;
public class Session
{
void btnLoginClick()
{
NombreUsuario = Username.Text;
Application.Current.Properties["name"] = NombreUsuario;
Application.Current.Properties["IsLoggedIn"] = true;
}
}
i have this error
'MediaTypeNames.Application' does not contain a definition for 'Current'
My app:
namespace Dinamic.Trailer.Mobile.Forms
{
public partial class App : Application
{
public App()
{
Locator.ConfigureIoC();
InitializeComponent();
}
protected override async void OnStart()
{
await InitNavigation();
}
//onsleep()//OnStart
private Task InitNavigation()
{
var navigationService = Content.Resolve<MainNavigation>();
return navigationService.InitializeAsync();
}
}
}
Remove this line
using static System.Net.Mime.MediaTypeNames;
And use import the using Xamarin.Forms;
After that you can use Application.Current.Properties["key"] = value;
Use using xamarin.forms namespace while you use Application.Current.Properties for storing data. Either you could use App.Current.Properties if you do not want to add xamarin.forms namespace in your cs file.
Here App refer your App class in App.xaml.cs which inherit from Xamarin.forms.Application. so you can use App.Current.Properties instead Application.Current.Properties.
Thank you.
I am new to xUnit and with the help of Prism Template Studio I created new Prism xUnit test project, which by default created one PrismAppMock.cs file as below:
// This should implement your application class -- What does it means?
public class PrismAppMock : PrismApplicationBase
{
public PrismAppMock(IPlatformInitializer initializer)
: base(initializer)
{
}
protected override IContainerExtension CreateContainerExtension()
{
return null;
}
protected override void OnInitialized()
{
}
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
}
}
On running the test it is throwing null exception as container is not resolved.
I tried to use UnityContainerExtension but as it is abstract class I can't use it directly.
protected override IContainerExtension CreateContainerExtension()
{
return new UnityContainerExtension();
}
Can anybody suggest on how to initialise PrismAppMock for unit testing.
I'm new to Xamarin and Prism, so forgive me if I'm missing something obvious. I am following the example of this project in GitHub. However, I am getting the following error when running my Android project.
System.InvalidOperationException: The current type, MyApp.Abstractions.IFacebookManager, is an interface and cannot be constructed. Are you missing a type mapping?
The error is occurring in EntryPage.xaml.g.cs in the LoadFromXaml() method.
[global::Xamarin.Forms.Xaml.XamlFilePathAttribute("Views\\EntryPage.xaml")]
public partial class EntryPage : global::Xamarin.Forms.ContentPage {
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Xamarin.Forms.Build.Tasks.XamlG", "2.0.0.0")]
private void InitializeComponent() {
// Exception thrown here!
global::Xamarin.Forms.Xaml.Extensions.LoadFromXaml(this, typeof(EntryPage));
}
}
This leads me to believe that I'm not using the IoC container properly, but I can't see what I'm doing differently from the example. The EntryPageViewModel's constructor takes IFacebookManager as a parameter and I understand that Unity should take care of this. I have a breakpoint on the constructor, but it's not being hit. This is a .NET Standard Xamarin solution. I would appreciate any help and guidance. Thank you!
Here's my App.xaml.cs
using MyApp.Abstractions;
using MyApp.Helpers;
using MyApp.Services;
using MyApp.ViewModels;
using MyApp.Views;
using Prism;
using Prism.Ioc;
using Prism.Unity;
using Xamarin.Forms;
namespace MyApp
{
public partial class App : PrismApplication
{
public App(IPlatformInitializer initializer = null) : base(initializer) { }
protected override void OnInitialized()
{
InitializeComponent();
ServiceResolver.Instance.Add<ICloudService, AzureCloudService>();
NavigationService.NavigateAsync("NavigationPage/EntryPage");
}
protected override void RegisterTypes(IContainerRegistry containerRegistry)
{
containerRegistry.RegisterForNavigation<NavigationPage>();
containerRegistry.RegisterForNavigation<EntryPage, EntryPageViewModel>();
}
}
}
Here's my MainActivity.cs
using Android.App;
using Android.Content.PM;
using Android.OS;
using MyApp.Droid.Services;
using MyApp.Abstractions;
using Android.Content;
using Xamarin.Facebook;
using Xamarin.Forms;
using Prism;
using Prism.Ioc;
namespace MyApp.Droid
{
[Activity(Label = "MyApp", Icon = "#drawable/icon", Theme = "#style/MainTheme", Name = "com.mydomain.myapp.MainActivity", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
ICallbackManager fbCallbackManager;
AndroidLoginProvider loginProvider;
protected override void OnCreate(Bundle bundle)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(bundle);
Microsoft.WindowsAzure.MobileServices.CurrentPlatform.Init();
global::Xamarin.Forms.Forms.Init(this, bundle);
DependencyService.Register<IFacebookManager, FacebookManager>();
LoadApplication(new App(new AndroidInitializer()));
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
var manager = DependencyService.Get<IFacebookManager>();
if (manager != null)
{
(manager as FacebookManager)._callbackManager.OnActivityResult(requestCode, (int)resultCode, data);
}
}
}
public class AndroidInitializer : IPlatformInitializer
{
public void RegisterTypes(IContainerRegistry containerRegistry)
{
}
}
}
public class AndroidInitializer : IPlatformInitializer
{
public void RegisterTypes(IContainerRegistry containerRegistry)
{
}
}
You are mixing the Xamarin Forms Dependency Service with the one provided with Prism.Unity
Instead of calling DependencyService.Register<IFacebookManager, FacebookManager>();
You need to register it with the AndroidInitializer .
public class AndroidInitializer : IPlatformInitializer
{
public void RegisterTypes(IContainerRegistry container)
{
container.RegisterSingleton<IFacebookManager, FacebookManager>();
}
}
You can then always resolve a dependency manually by calling App.Container.Resolve inside OnActivityResult.
To complete the previous answer that helped me a lot to fix a similar issue:
with prism 7, you need to resolve a dependency via IContainerProvider as follow:
var container = (App.Current as Prism.Unity.PrismApplication).Container;
var manager = container.Resolve<IFacebookManager>();
In this case, Unity is used as the IoC "container"
I want to call a base.Dispose() on the OnDisappearing() from my Android project in Xamarin.Forms.
I have done something like this :-
namespace Project.Mobile.Droid
{
[assembly: ExportRenderer(typeof(ItemListPage), typeof(DisposeRenderer))]
class DisposeRenderer : ViewRenderer
{
public DisposeRenderer() { }
}
}
How can I go ahead with this?
Iam new to Xamarin.Forms, so it would be a great help if someone helps me on this.
As long as your ItemListPage implements IDisposable, you could try the following :-
using System;
using DisposableControlSample;
using DisposableControlSample.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
[assembly: ExportRenderer(typeof(DisposablePage), typeof(DisposablePageRenderer))]
namespace DisposableControlSample.Droid
{
public class DisposablePageRenderer : PageRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Page> e)
{
base.OnElementChanged(e);
e.NewElement.Disappearing += (sender, args) =>
{
var disposablePage = sender as IDisposable;
if (disposablePage != null)
{
disposablePage.Dispose();
}
};
}
}
}