Finish buttons_demo

Runtime/material/tab_controller.cs

         }
     }
 
-    class DefaultTabController : StatefulWidget {
+    public class DefaultTabController : StatefulWidget {
         public DefaultTabController(
             Key key = null,
             int? length = null,

Samples/UIWidgetsGallery/demo/material/buttons_demo.cs

 namespace UIWidgetsGallery.gallery {
 
 class ButtonsDemo : StatefulWidget {
-  const String routeName = "/material/buttons";
+  public const String routeName = "/material/buttons";
 
   public ButtonsDemo(Key key = null) : base(key: key) {
       
                                     this.dropdown1Value = newValue;
                                 });
                             },
-                            items: new List<string> {"One", "Two", "Free", "Four"}.map<DropdownMenuItem<String>>((string value) => {
+                            items: new List<string> {"One", "Two", "Free", "Four"}.Select((string value) => {
-                            }).toList()
+                            }).ToList()
                         )
                     ),
                     new SizedBox (
                                     this.dropdown2Value = newValue;
                                 });
                             },
-                            items: new List<String >{"One", "Two", "Free", "Four"}.map<DropdownMenuItem<String>>((string value) => {
+                            items: new List<String >{"One", "Two", "Free", "Four"}.Select((string value) => {
-                            }).toList()
+                            }).ToList()
                         )
                     ),
                     new SizedBox (

Samples/UIWidgetsGallery/gallery/demo.cs

         string _exampleCode;
 
         public override void didChangeDependencies() {
-            ExampleCodeParser.getExampleCode(this.widget.exampleCodeTag, DefaultAssetBundle.of(this.context)).Then(
+            new ExampleCodeParser().getExampleCode(this.widget.exampleCodeTag, DefaultAssetBundle.of(this.context)).Then(
                 (string code) => {
                     if (this.mounted) {
                         this.setState(() => { this._exampleCode = code ?? "Example code not found"; });
             Widget body;
             if (this._exampleCode == null) {
                 body = new Center(
-                    child: CircularProgressIndicator()
+                    child: new CircularProgressIndicator()
                 );
             }
             else {

Samples/UIWidgetsGallery/gallery/demos.cs

 //                    documentationUrl: "https://docs.flutter.io/flutter/material/ScaffoldState/showBottomSheet.html",
 //                    buildRoute: (BuildContext context) => PersistentBottomSheetDemo()
 //                ),
-//                new GalleryDemo(
-//                    title: "Buttons",
-//                    subtitle: "Flat, raised, dropdown, and more",
-//                    icon: GalleryIcons.generic_buttons,
-//                    category: GalleryDemoCategory._kMaterialComponents,
-//                    routeName: ButtonsDemo.routeName,
-//                    buildRoute: (BuildContext context) => ButtonsDemo()
-//                ),
+                new GalleryDemo(
+                    title: "Buttons",
+                    subtitle: "Flat, raised, dropdown, and more",
+                    icon: GalleryIcons.generic_buttons,
+                    category: DemoUtils._kMaterialComponents,
+                    routeName: ButtonsDemo.routeName,
+                    buildRoute: (BuildContext context) => new ButtonsDemo()
+                ),
 //                new GalleryDemo(
 //                    title: "Buttons: Floating Action Button",
 //                    subtitle: "FAB with transitions",