Height = 0 in OnSizeChanged method

    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        global::Xamarin.Forms.Forms.Init (this, bundle);
        LoadApplication (new App ());
        SetContentView(Resource.Layout.Main);
        LinearLayout mainLayout = FindViewById<LinearLayout>(Resource.Id.MyLinearLayout);
        var myLayout = new MyLayout(Android.App.Application.Context);
        mainLayout.AddView (MyLayout);
    }



    public class MyLayout : RelativeLayout
    {
        protected override void OnSizeChanged(int w, int h, int oldw, int oldh)
        {
            // w = 800, h = 0
            base.OnSizeChanged(w, h, oldw, oldh);
        }
    }

I want to add my layout on page and change size of my layout when it will be needed.

Width is determined correctly.
But height is always equals 0.