Updating sample code for BottomNavigationBar class for diagram. (#30453)

packages/flutter/lib/src/material/bottom_navigation_bar.dart

@@ -66,15 +66,25 @@ enum BottomNavigationBarType {
 /// This example shows a [BottomNavigationBar] as it is used within a [Scaffold]
 /// widget. The [BottomNavigationBar] has three [BottomNavigationBarItem]
 /// widgets and the [currentIndex] is set to index 1. The selected item is
-/// purple. The `_onItemTapped` function changes the selected item's index
+/// amber. The `_onItemTapped` function changes the selected item's index
 /// and displays a corresponding message in the center of the [Scaffold].
 ///
 /// ```dart
 /// int _selectedIndex = 1;
-/// static const List<Widget> _widgetOptions = const <Widget>[
-///   Text('Index 0: Home'),
-///   Text('Index 1: Business'),
-///   Text('Index 2: School'),
+/// static const TextStyle optionStyle = TextStyle(fontSize: 30, fontWeight: FontWeight.bold);
+/// static const List<Widget> _widgetOptions = <Widget>[
+///   Text(
+///     'Index 0: Home',
+///     style: optionStyle,
+///   ),
+///   Text(
+///      'Index 1: Business',
+///      style: optionStyle,
+///   ),
+///   Text(
+///      'Index 2: School',
+///      style: optionStyle,
+///   ),
 /// ];
 ///
 /// void _onItemTapped(int index) {
@@ -87,19 +97,28 @@ enum BottomNavigationBarType {
 /// Widget build(BuildContext context) {
 ///   return Scaffold(
 ///     appBar: AppBar(
-///       title: Text('BottomNavigationBar Sample'),
+///       title: const Text('BottomNavigationBar Sample'),
 ///     ),
 ///     body: Center(
 ///       child: _widgetOptions.elementAt(_selectedIndex),
 ///     ),
 ///     bottomNavigationBar: BottomNavigationBar(
-///       items: <BottomNavigationBarItem>[
-///         BottomNavigationBarItem(icon: Icon(Icons.home), title: Text('Home')),
-///         BottomNavigationBarItem(icon: Icon(Icons.business), title: Text('Business')),
-///         BottomNavigationBarItem(icon: Icon(Icons.school), title: Text('School')),
+///       items: const <BottomNavigationBarItem>[
+///         BottomNavigationBarItem(
+///           icon: Icon(Icons.home),
+///           title: Text('Home'),
+///         ),
+///         BottomNavigationBarItem(
+///           icon: Icon(Icons.business),
+///           title: Text('Business'),
+///         ),
+///         BottomNavigationBarItem(
+///           icon: Icon(Icons.school),
+///           title: Text('School'),
+///         ),
 ///       ],
 ///       currentIndex: _selectedIndex,
-///       selectedItemColor: Colors.deepPurple,
+///       selectedItemColor: Colors.amber[800],
 ///       onTap: _onItemTapped,
 ///     ),
 ///   );