Update to ListView Sample Code in API Docs (#29072)
* Updated ListView Sample code with more examples for different constructors and also to match asset diagrams.
* Fixed MIA semicolons.
* Code cleanup.
* Added context for ListView.builder example.
* Analyzer does not like const and static usages.
* Replaced the const declarations with final. The analyzer does not like the use of const here, at all.
* Fixed parameterized declarations.
diff --git a/packages/flutter/lib/src/widgets/scroll_view.dart b/packages/flutter/lib/src/widgets/scroll_view.dart
index 0dbec87..0f28527 100644
--- a/packages/flutter/lib/src/widgets/scroll_view.dart
+++ b/packages/flutter/lib/src/widgets/scroll_view.dart
@@ -604,19 +604,78 @@
/// padding. To avoid this behavior, override with a zero [padding] property.
///
/// {@tool sample}
-///
-/// An infinite list of children:
+/// This example uses the default constructor for [ListView] which takes an
+/// explicit [List<Widget>] of children. This [ListView]'s children are made up
+/// of [Container]s with [Text].
///
/// ```dart
-/// ListView.builder(
-/// padding: EdgeInsets.all(8.0),
-/// itemExtent: 20.0,
-/// itemBuilder: (BuildContext context, int index) {
-/// return Text('entry $index');
-/// },
+/// ListView(
+/// padding: const EdgeInsets.all(8.0),
+/// children: <Widget>[
+/// Container(
+/// height: 50,
+/// color: Colors.amber[600],
+/// child: const Center(child: Text('Entry A')),
+/// ),
+/// Container(
+/// height: 50,
+/// color: Colors.amber[500],
+/// child: const Center(child: Text('Entry B')),
+/// ),
+/// Container(
+/// height: 50,
+/// color: Colors.amber[100],
+/// child: const Center(child: Text('Entry C')),
+/// ),
+/// ],
/// )
/// ```
/// {@end-tool}
+/// {@tool sample}
+/// This example mirrors the previous one, creating the same list using the
+/// [ListView.builder] constructor. Using the [IndexedWidgetBuilder], children
+/// are built lazily and can be infinite in number.
+///
+/// ```dart
+/// final List<String> entries = <String>['A', 'B', 'C'];
+/// final List<int> colorCodes = <int>[600, 500, 100];
+///
+/// ListView.builder(
+/// padding: const EdgeInsets.all(8.0),
+/// itemCount: entries.length,
+/// itemBuilder: (BuildContext context, int index) {
+/// return Container(
+/// height: 50,
+/// color: Colors.amber[colorCodes[index]],
+/// child: Center(child: Text('Entry ${entries[index]}')),
+/// );
+/// }
+/// );
+/// ```
+/// {@end-tool}
+/// {@tool sample}
+/// This example continues to build from our the previous ones, creating a
+/// similar list using [ListView.separated]. Here, a [Divider] is used as a
+/// separator.
+///
+/// ```dart
+/// final List<String> entries = <String>['A', 'B', 'C'];
+/// final List<int> colorCodes = <int>[600, 500, 100];
+///
+/// ListView.separated(
+/// padding: const EdgeInsets.all(8.0),
+/// itemCount: entries.length,
+/// itemBuilder: (BuildContext context, int index) {
+/// return Container(
+/// height: 50,
+/// color: Colors.amber[colorCodes[index]],
+/// child: Center(child: Text('Entry ${entries[index]}')),
+/// );
+/// },
+/// separatorBuilder: (BuildContext context, int index) => const Divider(),
+/// );
+/// ```
+/// {@end-tool}
///
/// ## Child elements' lifecycle
///
