Every API needs authentication, yet no developer wants to deal with authentication. Simple Auth embeds authentication into the API so you dont need to deal with it. Most importantly it works great with traditional Xamarin and Xamarin.Forms

https://www.nuget.org/packages/Clancey.SimpleAuth/

Simple auth ships with some built in providers so you just need to add your keys and scopes.

var scopes = new[]
{
	"https://www.googleapis.com/auth/userinfo.email",
	"https://www.googleapis.com/auth/userinfo.profile"
};
var api = new GoogleApi("google",
	   "clientid",
	   "clientsecret")
{
	Scopes = scopes,
};

var account = await api.Authenticate();

Restful Api Requests couldnt be simpler

var song = await api.Get<Song>("http://myapi/Song/",songId);

The webview is automatically displayed for you. If you want to handle displaying it your self you can!

Api.ShowAuthenticator = (authenticator) =>
{
	var invoker = new Foundation.NSObject();
	invoker.BeginInvokeOnMainThread(() =>
	{
		var vc = new iOS.WebAuthenticator(authenticator);
		//TODO: Present View Controller
	});
};

On password support is for iOS Only.
Simply add the project or the Nuget

https://www.nuget.org/packages/Clancey.SimpleAuth.OnePassword/

Then call the following line in your iOS project prior to calling api.Authenticate();

SimpleAuth.OnePassword.Activate();