fix issue

Billing.Shared/UI/BillingPage.cs

@@ -1,14 +1,22 @@
-using Billing.Themes;
+using System;
+using Billing.Themes;
 using Xamarin.Forms;
 
 namespace Billing.UI
 {
     public abstract class BillingPage : ContentPage
     {
+        public event EventHandler Loaded;
+
         public BillingPage()
         {
             SetDynamicResource(BackgroundColorProperty, BaseTheme.WindowBackgroundColor);
             Shell.SetTabBarIsVisible(this, false);
         }
+
+        public virtual void OnLoaded()
+        {
+            Loaded?.Invoke(this, EventArgs.Empty);
+        }
     }
 }

Billing.Shared/UI/OptionsCells.cs

@@ -1,5 +1,6 @@
 using Billing.Themes;
 using System;
+using System.Threading.Tasks;
 using Xamarin.Forms;
 
 namespace Billing.UI
@@ -377,7 +378,17 @@ namespace Billing.UI
             set => SetValue(PlaceholderProperty, value);
         }
 
-        protected override View Content => new OptionEditor
+        OptionEditor editor;
+
+        public void SetFocus()
+        {
+            if (editor != null)
+            {
+                editor.Focus();
+            }
+        }
+
+        protected override View Content => editor = new OptionEditor
         {
             HorizontalOptions = LayoutOptions.Fill,
             VerticalOptions = LayoutOptions.Fill