Improve getting the current context

Summary

Getting the current activity is not done quite correctly.

public static partial class Platform
{
    static Activity currentActivity;

    internal static Activity AppActivity
         => currentActivity
        ?? throw ExeptionHelper.ActivityNotDetected;
}

Permalink

Maybe we could replace this with a IActivityLifecycleCallbacks or the Android.App.Application.Context

[dimonovdd]

var page = Forms.Application.Current.MainPage;

@pictos @ahoefling Hi. Thanks. I would not like to add a dependency on Xamarin.Forms to the plugin I could use a Android.Content.Context but then I won’t be able to call StartActivityForResult method

I have one idea, I will try to do it soon. I’ll be happy if you watch it.

[SkyeHoefling]

That won’t work because this does not take a dependency on Xamarin.Forms. I am going to try and submit a PR for you all to look at that might solve this problem.