CS1729 'Application' does not contain a constructor that takes 1 arguments - xamarin

Question

I created a OAuth2Service class in my Xamarin Forms Android Project which inherits a IOAuth2Service interface.I need this to be available in my class library so i can perform google authentication in my Xamarin forms Application. But I keep getting the error message mentioned above despite the fact that i setup the application class to accept an argument of type IOAuth2Service. Here's my "App.Xaml.cs" which contains the Application class. What should i do?
public partial class Application : Xamarin.Forms.Application
{
public Application(IOAuth2Service oAuth2Service)
{
InitializeComponent();
MainPage = new NavigationPage(new LoginPage(oAuth2Service));
}
protected override void OnStart()
{
AppCenter.Start("android=ced94d85-cb85-4ec2-8411-96864a7ec23e;" +
"uwp={Your UWP App secret here};" +
"ios={Your iOS App secret here}",
typeof(Analytics), typeof(Crashes));
}
}

Answer 1

The IOAuth2Service is actually a Interface and not a class. I don't think you can create an instance object from an interface. And i'm correct cause after making the changes you suggested. I get the error:"Cannot create an instance of the abstract class or interface 'IOAuth2Service'"

Answer 2

Why not the instantiate the OAuth2Service class in the Constructor of Applicationlike following code? Put OAuth2Service class in PCL.
public Application()
{
InitializeComponent();
OAuth2Service oAuth2Service=new OAuth2Service ();
MainPage = new NavigationPage(new LoginPage(oAuth2Service));
}
If IOAuth2Service in the xxxxx.Droid or xxxxx.IOS folder. You need transfer IOAuth2Service to the PCL. In Android, You can instantiate it in OnCreate method of MainActivity.cs
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
OAuth2Service oAuth2Service = new OAuth2Service ();
LoadApplication(new App(oAuth2Service));
}
In IOS, You can instantiate it in FinishedLaunching method of AppDelegate.cs
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
global::Xamarin.Forms.Forms.Init();
OAuth2Service oAuth2Service = new OAuth2Service ();
LoadApplication(new App(oAuth2Service));
return base.FinishedLaunching(app, options);
}
Here is Application class.
public partial class Application : Xamarin.Forms.Application
{
public Application(OAuth2Service oAuth2Service)
{
InitializeComponent();
MainPage = new NavigationPage(new LoginPage(oAuth2Service));
}
}