Add SliverGrid.list convenience constructor (flutter#173925)

This PR adds a new `SliverGrid.list` convenience constructor that
accepts a `List<Widget> children` parameter, providing a cleaner API
compared to manually creating `SliverChildListDelegate`.

## What was added

The constructor uses `SliverChildListDelegate` internally and follows
the same pattern as existing convenience constructors like
`SliverGrid.count` and `SliverGrid.extent`. This addresses the use case
where developers want to create sliver grids with predefined widget
lists without the verbosity of manually constructing the delegate.

## Before/After comparison

**Before:**
```dart
SliverGrid(
  gridDelegate: gridDelegate,
  delegate: SliverChildListDelegate([widget1, widget2, widget3]),
)
```

**After:**
```dart
SliverGrid.list(
  gridDelegate: gridDelegate,
  children: [widget1, widget2, widget3],
)
```

## Implementation details

- Added `SliverGrid.list` constructor in
`packages/flutter/lib/src/widgets/sliver.dart`
- Constructor accepts `List<Widget> children` and all necessary delegate
configuration parameters
- Uses `SliverChildListDelegate` internally for consistent behavior
- Added comprehensive test coverage in
`packages/flutter/test/widgets/slivers_test.dart`

## Issue addressed

Fixes: flutter#173018

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

---------

Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

Author: 2 people

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

@@ -803,6 +803,60 @@ class SliverGrid extends SliverMultiBoxAdaptorWidget {
        ),
        super(delegate: SliverChildListDelegate(children));
 
+  /// Creates a sliver that places multiple box children in a two dimensional
+  /// arrangement.
+  ///
+  /// _To learn more about slivers, see [CustomScrollView.slivers]._
+  ///
+  /// Uses a [SliverChildListDelegate] as the [delegate].
+  ///
+  /// The `addAutomaticKeepAlives` argument corresponds to the
+  /// [SliverChildListDelegate.addAutomaticKeepAlives] property. The
+  /// `addRepaintBoundaries` argument corresponds to the
+  /// [SliverChildListDelegate.addRepaintBoundaries] property. The
+  /// `addSemanticIndexes` argument corresponds to the
+  /// [SliverChildListDelegate.addSemanticIndexes] property. The
+  /// `semanticIndexOffset` argument corresponds to the
+  /// [SliverChildListDelegate.semanticIndexOffset] property.
+  ///
+  /// {@tool snippet}
+  /// This example, which would be inserted into a [CustomScrollView.slivers]
+  /// list, shows a grid of [Container] widgets.
+  ///
+  /// ```dart
+  /// SliverGrid.list(
+  ///   gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+  ///     crossAxisCount: 3,
+  ///   ),
+  ///   children: <Widget>[
+  ///     Container(color: Colors.red),
+  ///     Container(color: Colors.green),
+  ///     Container(color: Colors.blue),
+  ///     Container(color: Colors.yellow),
+  ///     Container(color: Colors.orange),
+  ///     Container(color: Colors.purple),
+  ///   ],
+  /// );
+  /// ```
+  /// {@end-tool}
+  SliverGrid.list({
+    super.key,
+    required this.gridDelegate,
+    required List<Widget> children,
+    bool addAutomaticKeepAlives = true,
+    bool addRepaintBoundaries = true,
+    bool addSemanticIndexes = true,
+    int semanticIndexOffset = 0,
+  }) : super(
+         delegate: SliverChildListDelegate(
+           children,
+           addAutomaticKeepAlives: addAutomaticKeepAlives,
+           addRepaintBoundaries: addRepaintBoundaries,
+           addSemanticIndexes: addSemanticIndexes,
+           semanticIndexOffset: semanticIndexOffset,
+         ),
+       );
+
   /// The delegate that controls the size and position of the children.
   final SliverGridDelegate gridDelegate;
 

packages/flutter/test/widgets/slivers_test.dart

@@ -1389,6 +1389,65 @@ void main() {
     expect(secondTapped, 1);
   });
 
+  testWidgets('SliverGrid.list can display 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>[
+              SliverGrid.list(
+                gridDelegate: _TestArbitrarySliverGridDelegate(),
+                children: <Widget>[
+                  Material(
+                    color: Colors.yellow,
+                    child: InkWell(onTap: () => firstTapped++, child: const Text('First')),
+                  ),
+                  Material(
+                    color: Colors.red,
+                    child: InkWell(onTap: () => secondTapped++, child: const Text('Second')),
+                  ),
+                ],
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    // Verify correct hit testing
+    await tester.tap(find.text('First'));
+    expect(firstTapped, 1);
+    expect(secondTapped, 0);
+    firstTapped = 0;
+    await tester.tap(find.text('Second'));
+    expect(firstTapped, 0);
+    expect(secondTapped, 1);
+  });
+
+  testWidgets('SliverGrid.list with empty children list', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: CustomScrollView(
+            slivers: <Widget>[
+              SliverGrid.list(
+                gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),
+                children: const <Widget>[],
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    // Should render without errors - the SliverGrid should be present even with empty children
+    expect(find.byType(CustomScrollView), findsOneWidget);
+  });
+
   testWidgets('SliverGridRegularTileLayout.computeMaxScrollOffset handles 0 children', (
     WidgetTester tester,
   ) async {