content dimensions are not established get controller value error

Author: hello-coder-xu

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

@@ -384,10 +384,10 @@ class _PagePosition extends ScrollPositionWithSingleContext implements PageMetri
   @override
   double? get page {
     assert(
-      !hasPixels || hasContentDimensions,
+      !hasPixels || hasContentDimensions || !haveDimensions,
       'Page value is only available after content dimensions are established.',
     );
-    return !hasPixels || !hasContentDimensions
+    return !hasPixels || !(hasContentDimensions || haveDimensions)
       ? null
       : _cachedPage ?? getPageFromPixels(clampDouble(pixels, minScrollExtent, maxScrollExtent), viewportDimension);
   }

packages/flutter/test/widgets/page_view_test.dart

@@ -1372,4 +1372,27 @@ void main() {
       await tester.pumpWidget(createPageView(null));
     });
   });
+
+
+  testWidgets('content dimensions are not established get controller value error', (WidgetTester tester) async {
+    final PageController controller = PageController();
+    addTearDown(controller.dispose);
+    await tester.pumpWidget(MaterialApp(
+      home: Scaffold(
+        body: PageView(
+          controller: controller,
+          children: <Widget>[
+            Builder(
+              builder: (BuildContext context) {
+                final double currentPage = controller.hasClients ? controller.page ?? -1.0 : -2.0;
+                return Center(child: Text(currentPage.toString()));
+              },
+            ),
+          ],
+        ),
+      ),
+    ));
+
+    expect(find.text('-1.0'), findsOneWidget);
+  });
 }