Add scrollbars to Gallery (#33634)

examples/flutter_gallery/lib/demo/colors_demo.dart

@@ -115,9 +115,11 @@ class PaletteTabView extends StatelessWidget {
       }).toList());
     }
 
-    return ListView(
+    return Scrollbar(
+      child: ListView(
         itemExtent: kColorItemHeight,
         children: colorItems,
+      )
     );
   }
 }

examples/flutter_gallery/lib/demo/cupertino/cupertino_alert_demo.dart

@@ -54,7 +54,8 @@ class _CupertinoAlertDemoState extends State<CupertinoAlertDemo> {
         child: Builder(
           builder: (BuildContext context) {
             final List<Widget> stackChildren = <Widget>[
-              ListView(
+              CupertinoScrollbar(
+                child: ListView(
                   // Add more padding to the normal safe area.
                   padding: const EdgeInsets.symmetric(vertical: 24.0, horizontal: 72.0)
                       + MediaQuery.of(context).padding,
@@ -185,6 +186,7 @@ class _CupertinoAlertDemoState extends State<CupertinoAlertDemo> {
                     ),
                   ],
                 ),
+              ),
             ];
 
             if (lastSelectedValue != null) {

examples/flutter_gallery/lib/demo/cupertino/cupertino_navigation_demo.dart

@@ -430,11 +430,13 @@ class CupertinoDemoTab2 extends StatelessWidget {
       navigationBar: CupertinoNavigationBar(
         trailing: trailingButtons,
       ),
+      child: CupertinoScrollbar(
         child: ListView(
           children: <Widget>[
             Tab2Header(),
           ]..addAll(buildTab2Conversation()),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/cupertino/cupertino_text_field_demo.dart

@@ -166,6 +166,7 @@ class _CupertinoTextFieldDemoState extends State<CupertinoTextFieldDemo> {
           previousPageTitle: 'Cupertino',
           middle: Text('Text Fields'),
         ),
+        child: CupertinoScrollbar(
           child: ListView(
             children: <Widget>[
               Padding(
@@ -187,6 +188,7 @@ class _CupertinoTextFieldDemoState extends State<CupertinoTextFieldDemo> {
             ],
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/backdrop_demo.dart

@@ -102,7 +102,8 @@ class CategoryView extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
-    return ListView(
+    return Scrollbar(
+      child: ListView(
         key: PageStorageKey<Category>(category),
         padding: const EdgeInsets.symmetric(
           vertical: 16.0,
@@ -139,6 +140,7 @@ class CategoryView extends StatelessWidget {
             ],
           );
         }).toList(),
+      )
     );
   }
 }

examples/flutter_gallery/lib/demo/material/bottom_app_bar_demo.dart

@@ -156,7 +156,8 @@ class _BottomAppBarDemoState extends State<BottomAppBarDemo> {
           ),
         ],
       ),
-      body: ListView(
+      body: Scrollbar(
+        child: ListView(
           padding: const EdgeInsets.only(bottom: 88.0),
           children: <Widget>[
             const _Heading('FAB Shape'),
@@ -185,6 +186,7 @@ class _BottomAppBarDemoState extends State<BottomAppBarDemo> {
             _ColorsItem(kBabColors, _babColor, _onBabColorChanged),
           ],
         ),
+      ),
       floatingActionButton: _fabShape.value,
       floatingActionButtonLocation: _fabLocation.value,
       bottomNavigationBar: _DemoBottomAppBar(

examples/flutter_gallery/lib/demo/material/cards_demo.dart

@@ -388,7 +388,8 @@ class _CardsDemoState extends State<CardsDemo> {
           ),
         ],
       ),
-      body: ListView(
+      body: Scrollbar(
+        child: ListView(
           padding: const EdgeInsets.only(top: 8.0, left: 8.0, right: 8.0),
           children: destinations.map<Widget>((TravelDestination destination) {
             Widget child;
@@ -410,6 +411,7 @@ class _CardsDemoState extends State<CardsDemo> {
             );
           }).toList(),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/chip_demo.dart

@@ -324,7 +324,7 @@ class _ChipDemoState extends State<ChipDemo> {
                 borderRadius: BorderRadius.circular(10.0),
               ))
             : theme.chipTheme,
-        child: ListView(children: tiles),
+        child: Scrollbar(child: ListView(children: tiles)),
       ),
       floatingActionButton: FloatingActionButton(
         onPressed: () => setState(_reset),

examples/flutter_gallery/lib/demo/material/data_table_demo.dart

@@ -172,7 +172,8 @@ class _DataTableDemoState extends State<DataTableDemo> {
           MaterialDemoDocumentationButton(DataTableDemo.routeName),
         ],
       ),
-      body: ListView(
+      body: Scrollbar(
+        child: ListView(
           padding: const EdgeInsets.all(20.0),
           children: <Widget>[
             PaginatedDataTable(
@@ -229,6 +230,7 @@ class _DataTableDemoState extends State<DataTableDemo> {
             ),
           ],
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/elevation_demo.dart

@@ -57,9 +57,7 @@ class _ElevationDemoState extends State<ElevationDemo> {
           ),
         ],
       ),
-      body: ListView(
-        children: buildCards(),
-      ),
+      body: Scrollbar(child: ListView(children: buildCards())),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/expansion_tile_list_demo.dart

@@ -16,7 +16,8 @@ class ExpansionTileListDemo extends StatelessWidget {
         title: const Text('Expand/collapse list control'),
         actions: <Widget>[MaterialDemoDocumentationButton(routeName)],
       ),
-      body: ListView(
+      body: Scrollbar(
+        child: ListView(
           children: <Widget>[
             const ListTile(title: Text('Top')),
             ExpansionTile(
@@ -33,6 +34,7 @@ class ExpansionTileListDemo extends StatelessWidget {
             const ListTile(title: Text('Bottom')),
           ],
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/full_screen_dialog_demo.dart

@@ -162,6 +162,7 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
       ),
       body: Form(
         onWillPop: _onWillPop,
+        child: Scrollbar(
           child: ListView(
             padding: const EdgeInsets.all(16.0),
             children: <Widget>[
@@ -261,6 +262,7 @@ class FullScreenDialogDemoState extends State<FullScreenDialogDemo> {
             .toList(),
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/icons_demo.dart

@@ -58,6 +58,7 @@ class IconsDemoState extends State<IconsDemo> {
         child: SafeArea(
           top: false,
           bottom: false,
+          child: Scrollbar(
             child: ListView(
               padding: const EdgeInsets.all(24.0),
               children: <Widget>[
@@ -68,6 +69,7 @@ class IconsDemoState extends State<IconsDemo> {
             ),
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/leave_behind_demo.dart

@@ -130,7 +130,8 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
         ),
       );
     } else {
-      body = ListView(
+      body = Scrollbar(
+        child: ListView(
           children: leaveBehindItems.map<Widget>((LeaveBehindItem item) {
             return _LeaveBehindListItem(
               confirmDismiss: _confirmDismiss,
@@ -140,6 +141,7 @@ class LeaveBehindDemoState extends State<LeaveBehindDemo> {
               dismissDirection: _dismissDirection,
             );
           }).toList(),
+          ),
       );
     }
 

examples/flutter_gallery/lib/demo/material/overscroll_demo.dart

@@ -62,6 +62,7 @@ class OverscrollDemoState extends State<OverscrollDemo> {
       body: RefreshIndicator(
         key: _refreshIndicatorKey,
         onRefresh: _handleRefresh,
+        child: Scrollbar(
           child: ListView.builder(
             padding: kMaterialListPadding,
             itemCount: _items.length,
@@ -76,6 +77,7 @@ class OverscrollDemoState extends State<OverscrollDemo> {
             },
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/material/text_form_field_demo.dart

@@ -182,6 +182,7 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
           key: _formKey,
           autovalidate: _autovalidate,
           onWillPop: _warnUserAboutInvalidData,
+          child: Scrollbar(
             child: SingleChildScrollView(
               dragStartBehavior: DragStartBehavior.down,
               padding: const EdgeInsets.symmetric(horizontal: 16.0),
@@ -296,6 +297,7 @@ class TextFormFieldDemoState extends State<TextFormFieldDemo> {
             ),
           ),
         ),
+      ),
     );
   }
 }

examples/flutter_gallery/lib/demo/typography_demo.dart

@@ -73,7 +73,7 @@ class TypographyDemo extends StatelessWidget {
       body: SafeArea(
         top: false,
         bottom: false,
-        child: ListView(children: styleItems),
+        child: Scrollbar(child: ListView(children: styleItems)),
       ),
     );
   }

examples/flutter_gallery/lib/demo/video_demo.dart

@@ -405,6 +405,7 @@ class _VideoDemoState extends State<VideoDemo> with SingleTickerProviderStateMix
       ),
       body: isSupported
         ? ConnectivityOverlay(
+            child: Scrollbar(
               child: ListView(
                 children: <Widget>[
                   VideoCard(
@@ -419,6 +420,7 @@ class _VideoDemoState extends State<VideoDemo> with SingleTickerProviderStateMix
                   ),
                 ],
               ),
+            ),
             connectedCompleter: connectedCompleter,
             scaffoldKey: scaffoldKey,
           )