Switch to reusing renderers on Forms elements

Ooui.Forms/PageExtensions.cs

@@ -16,16 +16,24 @@ namespace Xamarin.Forms
             Ooui.UI.Publish (path, () => lazyPage.Value);
         }
 
-        public static Ooui.Element CreateElement (this Xamarin.Forms.Page page)
+        public static Ooui.Element GetOouiElement (this Xamarin.Forms.Page page)
         {
             if (!Xamarin.Forms.Forms.IsInitialized)
                 throw new InvalidOperationException ("call Forms.Init() before this");
             
+            var existingRenderer = Ooui.Forms.Platform.GetRenderer (page);
+            if (existingRenderer != null)
+                return existingRenderer.NativeView;
+
+            return CreateElement (page);
+        }
+
+        static Ooui.Element CreateElement (this Xamarin.Forms.Page page)
+        {
             if (!(page.RealParent is Application)) {
                 var app = new DefaultApplication ();
                 app.MainPage = page;
             }
-
             var result = new Ooui.Forms.Platform ();
             result.SetPage (page);
             return result.Element;

Samples/BoxViewClockSample.cs

@@ -7,9 +7,17 @@ namespace Samples
     {
         public string Title => "Xamarin.Forms BoxViewClock";
 
+        BoxViewClockPage page;
+
         public Ooui.Element CreateElement ()
         {
-            return new BoxViewClockPage ().CreateElement ();
+            //
+            // Always return the same page because the code never stops the timer
+            // and we don't want to create an unlimited number of them.
+            //
+            if (page == null)
+                page = new BoxViewClockPage ();
+            return page.GetOouiElement ();
         }
 
         class BoxViewClockPage : ContentPage

Samples/XamarinFormsSample.cs

@@ -44,12 +44,12 @@ namespace Samples
             var page = MakePage ();
             page.Publish ("/xamarin-forms-shared");
 
-            Ooui.UI.Publish ("/xamarin-forms", () => MakePage ().CreateElement ());
+            Ooui.UI.Publish ("/xamarin-forms", () => MakePage ().GetOouiElement ());
         }
 
         public Ooui.Element CreateElement ()
         {
-            return MakePage ().CreateElement ();
+            return MakePage ().GetOouiElement ();
         }
     }
 }