Revert "prevent pageView scrolling when calling ensureVisible (#67988)" (#68036)

This reverts commit 62cf4dbf.

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

@@ -341,9 +341,17 @@ class _PagePosition extends ScrollPositionWithSingleContext implements PageMetri
     RenderObject? targetRenderObject,
   }) {
     // Since the _PagePosition is intended to cover the available space within
-    // its viewport, stop trying to any scroll, otherwise, could end up changing
-    // which page is visible and moving the render object out of the viewport.
-    return Future<void>.value();
+    // its viewport, stop trying to move the target render object to the center
+    // - otherwise, could end up changing which page is visible and moving the
+    // targetRenderObject out of the viewport.
+    return super.ensureVisible(
+      object,
+      alignment: alignment,
+      duration: duration,
+      curve: curve,
+      alignmentPolicy: alignmentPolicy,
+      targetRenderObject: null,
+    );
   }
 
   @override

packages/flutter/test/widgets/scrollable_test.dart

@@ -1006,76 +1006,6 @@ void main() {
     expect(targetMidRightPage1, findsOneWidget);
     expect(targetMidLeftPage1, findsOneWidget);
   });
-
-  testWidgets('ensureVisible does not move PageViews when there are objects between pageView and target object', (WidgetTester tester) async {
-    final PageController controller = PageController();
-    int count = 0;
-
-    await tester.pumpWidget(
-      Directionality(
-        textDirection: TextDirection.ltr,
-        child: PageView(
-          controller: controller,
-          children: List<Widget>.generate(3, (int index) {
-            return Row(
-              children: <Widget>[
-                Container(
-                  width: 400,
-                  color: Colors.red,
-                ),
-                Expanded(
-                  child: Container(
-                    color: Colors.green,
-                    width: double.infinity,
-                    height: 50,
-                    child: SingleChildScrollView(
-                      scrollDirection: Axis.horizontal,
-                      child: Container(
-                        key: Key(index.toString()),
-                        color: Colors.yellow,
-                        height: 50,
-                        width: 200,
-                      ),
-                    ),
-                  ),
-                )
-              ],
-            );
-          }),
-        ),
-      ),
-    );
-
-    controller.position.addListener(() {
-      count++;
-    });
-
-    final Finder targetOfPage0 = find.byKey(const Key('0'));
-    final Finder targetOfPage1 = find.byKey(const Key('1'));
-
-    expect(targetOfPage0, findsOneWidget);
-    expect(targetOfPage1, findsNothing);
-
-    // `ensureVisible` should not trigger any scrolling or page changing of pageView.
-    await tester.ensureVisible(targetOfPage0);
-    await tester.pumpAndSettle();
-    expect(count, 0);
-    expect(targetOfPage0, findsOneWidget);
-    expect(targetOfPage1, findsNothing);
-
-    controller.jumpToPage(1);
-    await tester.pumpAndSettle();
-
-    expect(count, 1); // Trigger by `controller.jumpToPage(1)`
-    expect(targetOfPage0, findsNothing);
-    expect(targetOfPage1, findsOneWidget);
-
-    await tester.ensureVisible(targetOfPage1);
-    await tester.pumpAndSettle();
-    expect(count, 1);
-    expect(targetOfPage0, findsNothing);
-    expect(targetOfPage1, findsOneWidget);
-  });
 }
 
 // ignore: must_be_immutable