Add convenience constructors for SliverList (#116605)

* init

* lint

* add the other two slivers

* fix lint

* add test for sliverlist.separated

* add3 more

* fix lint and tests

* remove trailing spaces

* remove trailing spaces 2

* fix lint

* fix lint again

packages/flutter/lib/src/widgets/sliver_prototype_extent_list.dart

@@ -40,6 +40,109 @@ class SliverPrototypeExtentList extends SliverMultiBoxAdaptorWidget {
     required this.prototypeItem,
   }) : assert(prototypeItem != null);
 
+  /// A sliver that places its box children in a linear array and constrains them
+  /// to have the same extent as a prototype item along the main axis.
+  ///
+  /// This constructor is appropriate for sliver lists with a large (or
+  /// infinite) number of children whose extent is already determined.
+  ///
+  /// Providing a non-null `itemCount` improves the ability of the [SliverGrid]
+  /// to estimate the maximum scroll extent.
+  ///
+  /// `itemBuilder` will be called only with indices greater than or equal to
+  /// zero and less than `itemCount`.
+  ///
+  /// {@macro flutter.widgets.ListView.builder.itemBuilder}
+  ///
+  /// The `prototypeItem` argument is used to determine the extent of each item.
+  ///
+  /// {@macro flutter.widgets.PageView.findChildIndexCallback}
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
+  /// `addSemanticIndexes` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addSemanticIndexes] property.
+  ///
+  /// {@tool snippet}
+  /// This example, which would be inserted into a [CustomScrollView.slivers]
+  /// list, shows an infinite number of items in varying shades of blue:
+  ///
+  /// ```dart
+  /// SliverPrototypeExtentList.builder(
+  ///   prototypeItem: Container(
+  ///     alignment: Alignment.center,
+  ///     child: const Text('list item prototype'),
+  ///   ),
+  ///   itemBuilder: (BuildContext context, int index) {
+  ///     return Container(
+  ///       alignment: Alignment.center,
+  ///       color: Colors.lightBlue[100 * (index % 9)],
+  ///       child: Text('list item $index'),
+  ///     );
+  ///   },
+  /// )
+  /// ```
+  /// {@end-tool}
+  SliverPrototypeExtentList.builder({
+    super.key,
+    required NullableIndexedWidgetBuilder itemBuilder,
+    required this.prototypeItem,
+    ChildIndexGetter? findChildIndexCallback,
+    int? itemCount,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+  }) : super(delegate: SliverChildBuilderDelegate(
+         itemBuilder,
+         findChildIndexCallback: findChildIndexCallback,
+         childCount: itemCount,
+         addAutomaticKeepAlives: addAutomaticKeepAlives,
+         addRepaintBoundaries: addRepaintBoundaries,
+         addSemanticIndexes: addSemanticIndexes,
+       ));
+
+  /// A sliver that places multiple box children in a linear array along the main
+  /// axis.
+  ///
+  /// This constructor uses a list of [Widget]s to build the sliver.
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addRepaintBoundaries] property. The
+  /// `addSemanticIndexes` argument corresponds to the
+  /// [SliverChildBuilderDelegate.addSemanticIndexes] property.
+  ///
+  /// {@tool snippet}
+  /// This example, which would be inserted into a [CustomScrollView.slivers]
+  /// list, shows an infinite number of items in varying shades of blue:
+  ///
+  /// ```dart
+  /// SliverPrototypeExtentList.list(
+  ///   prototypeItem: const Text('Hello'),
+  ///   children: const <Widget>[
+  ///     Text('Hello'),
+  ///     Text('World!'),
+  ///   ],
+  /// );
+  /// ```
+  /// {@end-tool}
+  SliverPrototypeExtentList.list({
+    super.key,
+    required List<Widget> children,
+    required this.prototypeItem,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+  }) : super(delegate: SliverChildListDelegate(
+         children,
+         addAutomaticKeepAlives: addAutomaticKeepAlives,
+         addRepaintBoundaries: addRepaintBoundaries,
+         addSemanticIndexes: addSemanticIndexes,
+       ));
+
   /// Defines the main axis extent of all of this sliver's children.
   ///
   /// The [prototypeItem] is laid out before the rest of the sliver's children

packages/flutter/test/widgets/sliver_prototype_item_extent_test.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
-import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 class TestItem extends StatelessWidget {
@@ -41,6 +40,61 @@ Widget buildFrame({ int? count, double? width, double? height, Axis? scrollDirec
 }
 
 void main() {
+  testWidgets('SliverPrototypeExtentList.builder test', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: CustomScrollView(
+            slivers: <Widget>[
+              SliverPrototypeExtentList.builder(
+                itemBuilder: (BuildContext context, int index) => TestItem(item: index),
+                prototypeItem: const TestItem(item: -1, height: 100.0),
+                itemCount: 20,
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    // The viewport is 600 pixels high, lazily created items are 100 pixels high.
+    for (int i = 0; i < 6; i += 1) {
+      final Finder item = find.widgetWithText(Container, 'Item $i');
+      expect(item, findsOneWidget);
+      expect(tester.getTopLeft(item).dy, i * 100.0);
+      expect(tester.getSize(item).height, 100.0);
+    }
+    for (int i = 7; i < 20; i += 1) {
+      expect(find.text('Item $i'), findsNothing);
+    }
+  });
+
+  testWidgets('SliverPrototypeExtentList.builder test', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: CustomScrollView(
+            slivers: <Widget>[
+              SliverPrototypeExtentList.list(
+                prototypeItem: const TestItem(item: -1, height: 100.0),
+                children: <int>[0, 1, 2, 3, 4, 5, 6, 7].map((int index) => TestItem(item: index)).toList(),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    // The viewport is 600 pixels high, lazily created items are 100 pixels high.
+    for (int i = 0; i < 6; i += 1) {
+      final Finder item = find.widgetWithText(Container, 'Item $i');
+      expect(item, findsOneWidget);
+      expect(tester.getTopLeft(item).dy, i * 100.0);
+      expect(tester.getSize(item).height, 100.0);
+    }
+    expect(find.text('Item 7'), findsNothing);
+  });
+
   testWidgets('SliverPrototypeExtentList vertical scrolling basics', (WidgetTester tester) async {
     await tester.pumpWidget(buildFrame(count: 20, height: 100.0));
 

packages/flutter/test/widgets/slivers_test.dart

@@ -992,6 +992,264 @@ void main() {
     expect(secondTapped, 1);
   });
 
+  testWidgets('SliverList.builder can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverList.builder(
+              itemCount: 2,
+              itemBuilder: (BuildContext context, int index) {
+                return Material(
+                  color: index.isEven ? Colors.yellow : Colors.red,
+                  child: InkWell(
+                    onTap: () {
+                      index.isEven ? firstTapped++ : secondTapped++;
+                    },
+                    child: Text('Index $index'),
+                  ),
+                );
+              },
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+  testWidgets('SliverList.builder can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverList.builder(
+              itemCount: 2,
+              itemBuilder: (BuildContext context, int index) {
+                return Material(
+                  color: index.isEven ? Colors.yellow : Colors.red,
+                  child: InkWell(
+                    onTap: () {
+                      index.isEven ? firstTapped++ : secondTapped++;
+                    },
+                    child: Text('Index $index'),
+                  ),
+                );
+              },
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+  testWidgets('SliverList.separated can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverList.separated(
+              itemCount: 2,
+              itemBuilder: (BuildContext context, int index) {
+                return Material(
+                  color: index.isEven ? Colors.yellow : Colors.red,
+                  child: InkWell(
+                    onTap: () {
+                      index.isEven ? firstTapped++ : secondTapped++;
+                    },
+                    child: Text('Index $index'),
+                  ),
+                );
+              },
+              separatorBuilder: (BuildContext context, int index) => Text('Separator $index'),
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+  testWidgets('SliverList.separated has correct number of children', (WidgetTester tester) async {
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverList.separated(
+              itemCount: 2,
+              itemBuilder: (BuildContext context, int index) => const Text('item'),
+              separatorBuilder: (BuildContext context, int index) => const Text('separator'),
+            ),
+          ],
+        ),
+      ),
+    ));
+    expect(find.text('item'), findsNWidgets(2));
+    expect(find.text('separator'), findsNWidgets(1));
+  });
+
+  testWidgets('SliverList.list can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverList.list(
+              children: <Widget>[
+                Material(
+                  color: Colors.yellow,
+                  child: InkWell(
+                    onTap: () => firstTapped++,
+                    child: const Text('Index 0'),
+                  ),
+                ),
+                Material(
+                  color: Colors.red,
+                  child: InkWell(
+                    onTap: () => secondTapped++,
+                    child: const Text('Index 1'),
+                  ),
+                ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+  testWidgets('SliverFixedExtentList.builder can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverFixedExtentList.builder(
+              itemCount: 2,
+              itemExtent: 100,
+              itemBuilder: (BuildContext context, int index) {
+                return Material(
+                  color: index.isEven ? Colors.yellow : Colors.red,
+                  child: InkWell(
+                    onTap: () {
+                      index.isEven ? firstTapped++ : secondTapped++;
+                    },
+                    child: Text('Index $index'),
+                  ),
+                );
+              },
+            ),
+          ],
+        ),
+      ),
+    ));
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+    testWidgets('SliverList.list can build children', (WidgetTester tester) async {
+    int firstTapped = 0;
+    int secondTapped = 0;
+    final Key key = UniqueKey();
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        key: key,
+        body: CustomScrollView(
+          slivers: <Widget>[
+            SliverFixedExtentList.list(
+              itemExtent: 100,
+              children: <Widget>[
+                Material(
+                  color: Colors.yellow,
+                  child: InkWell(
+                    onTap: () => firstTapped++,
+                    child: const Text('Index 0'),
+                  ),
+                ),
+                Material(
+                  color: Colors.red,
+                  child: InkWell(
+                    onTap: () => secondTapped++,
+                    child: const Text('Index 1'),
+                  ),
+                ),
+              ],
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    // Verify correct hit testing
+    await tester.tap(find.text('Index 0'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Index 1'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
   testWidgets('SliverGrid.builder can build children', (WidgetTester tester) async {
     int firstTapped = 0;
     int secondTapped = 0;