From ddfaec19ad6dc6a0c6f4edb66295960a93597c1e Mon Sep 17 00:00:00 2001
From: Alexandre Daigle <alexandre@adaigle.ca>
Date: Tue, 17 Aug 2021 18:57:06 -0400
Subject: [PATCH] Fix null check for content dimensions in page getter (#87824)

---
 packages/flutter/lib/src/widgets/page_view.dart   | 6 ++++--
 packages/flutter/test/widgets/page_view_test.dart | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/packages/flutter/lib/src/widgets/page_view.dart b/packages/flutter/lib/src/widgets/page_view.dart
index 2a88557637..ed7e6a0e3d 100644
--- a/packages/flutter/lib/src/widgets/page_view.dart
+++ b/packages/flutter/lib/src/widgets/page_view.dart
@@ -385,10 +385,12 @@ class _PagePosition extends ScrollPositionWithSingleContext implements PageMetri
   @override
   double? get page {
     assert(
-      !hasPixels || (minScrollExtent != null && maxScrollExtent != null),
+      !hasPixels || hasContentDimensions,
       'Page value is only available after content dimensions are established.',
     );
-    return !hasPixels ? null : getPageFromPixels(pixels.clamp(minScrollExtent, maxScrollExtent), viewportDimension);
+    return !hasPixels || !hasContentDimensions
+      ? null
+      : getPageFromPixels(pixels.clamp(minScrollExtent, maxScrollExtent), viewportDimension);
   }
 
   @override
diff --git a/packages/flutter/test/widgets/page_view_test.dart b/packages/flutter/test/widgets/page_view_test.dart
index 2207fd229b..0ce4e6312a 100644
--- a/packages/flutter/test/widgets/page_view_test.dart
+++ b/packages/flutter/test/widgets/page_view_test.dart
@@ -14,6 +14,12 @@ import 'states.dart';
 const Duration _frameDuration = Duration(milliseconds: 100);
 
 void main() {
+  testWidgets('PageController cannot return page while unattached',
+      (WidgetTester tester) async {
+    final PageController controller = PageController();
+    expect(() => controller.page, throwsAssertionError);
+  });
+
   testWidgets('PageView control test', (WidgetTester tester) async {
     final List<String> log = <String>[];