Migration issue from 5.0.3 to 5.1.1 - Application is null / MvxFormsAppCompatActivity / base.OnCreate(bundle) / Resolved, but useful info

[mgoodfellow]

Steps to reproduce

The old method of setting up a view presenter in Setup.cs (Android) was to use something like:

protected override IMvxAndroidViewPresenter CreateViewPresenter()
{
    var presenter = new MvxFormsDroidPagePresenter();
    Mvx.RegisterSingleton<IMvxViewPresenter>(presenter);

    return presenter;
}

This unfortunately overrides the view presenter, and means that here in MvxFormsAppCompatActivity.cs won't resolve properly.

In turn this means that:

base.OnCreate(bundle); in your MainActivity when overriding MvxFormsAppCompatActivity will throw an NullReferenceException saying that "application is null`.

This had me banging my head against a wall for quite a long time, but I managed to work it out by looking at the new implementation in MvxFormsAndroidSetup.

I noticed that CreateFormsApplication was not being called - it might not be immediately obvious to other users updating from older MvvmCross versions!

Configuration

Version: 5.1.1

Platform:

• iOS
• Android
• WPF
• UWP