Expose padEnds on PageView widget (#78558)

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

@@ -637,6 +637,7 @@ class PageView extends StatefulWidget {
     this.restorationId,
     this.clipBehavior = Clip.hardEdge,
     this.scrollBehavior,
+    this.padEnds = true,
   }) : assert(allowImplicitScrolling != null),
        assert(clipBehavior != null),
        controller = controller ?? _defaultPageController,
@@ -676,6 +677,7 @@ class PageView extends StatefulWidget {
     this.restorationId,
     this.clipBehavior = Clip.hardEdge,
     this.scrollBehavior,
+    this.padEnds = true,
   }) : assert(allowImplicitScrolling != null),
        assert(clipBehavior != null),
        controller = controller ?? _defaultPageController,
@@ -780,6 +782,7 @@ class PageView extends StatefulWidget {
     this.restorationId,
     this.clipBehavior = Clip.hardEdge,
     this.scrollBehavior,
+    this.padEnds = true,
   }) : assert(childrenDelegate != null),
        assert(allowImplicitScrolling != null),
        assert(clipBehavior != null),
@@ -841,6 +844,10 @@ class PageView extends StatefulWidget {
   final ScrollPhysics? physics;
 
   /// Set to false to disable page snapping, useful for custom scroll behavior.
+  ///
+  /// If the [padEnds] is false and [PageController.viewportFraction] < 1.0,
+  /// the page will snap to the beginning of the viewport; otherwise, the page
+  /// will snap to the center of the viewport.
   final bool pageSnapping;
 
   /// Called whenever the page in the center of the viewport changes.
@@ -873,6 +880,17 @@ class PageView extends StatefulWidget {
   /// modified by default to not apply a [Scrollbar].
   final ScrollBehavior? scrollBehavior;
 
+  /// Whether to add padding to both ends of the list.
+  ///
+  /// If this is set to true and [PageController.viewportFraction] < 1.0, padding will be added
+  /// such that the first and last child slivers will be in the center of
+  /// the viewport when scrolled all the way to the start or end, respectively.
+  ///
+  /// If [PageController.viewportFraction] >= 1.0, this property has no effect.
+  ///
+  /// This property defaults to true and must not be null.
+  final bool padEnds;
+
   @override
   _PageViewState createState() => _PageViewState();
 }
@@ -942,6 +960,7 @@ class _PageViewState extends State<PageView> {
               SliverFillViewport(
                 viewportFraction: widget.controller.viewportFraction,
                 delegate: widget.childrenDelegate,
+                padEnds: widget.padEnds,
               ),
             ],
           );

packages/flutter/test/widgets/page_view_test.dart

@@ -985,4 +985,29 @@ void main() {
     renderObject.paint(context, Offset.zero);
     expect(context.clipBehavior, equals(Clip.antiAlias));
   });
+
+  testWidgets('PageView.padEnds tests', (WidgetTester tester) async {
+    Finder viewportFinder() => find.byType(SliverFillViewport, skipOffstage: false);
+
+    // PageView() defaults to true.
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: PageView(
+        children: const <Widget>[],
+      ),
+    ));
+
+    expect(tester.widget<SliverFillViewport>(viewportFinder()).padEnds, true);
+
+    // PageView(padEnds: false) is propagated properly.
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: PageView(
+        padEnds: false,
+        children: const <Widget>[],
+      ),
+    ));
+
+    expect(tester.widget<SliverFillViewport>(viewportFinder()).padEnds, false);
+  });
 }