fix nullability of ScrollMetrics (#65861)

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

@@ -308,10 +308,10 @@ class FixedExtentMetrics extends FixedScrollMetrics {
   /// Creates an immutable snapshot of values associated with a
   /// [ListWheelScrollView].
   FixedExtentMetrics({
-    required double minScrollExtent,
-    required double maxScrollExtent,
-    required double pixels,
-    required double viewportDimension,
+    required double? minScrollExtent,
+    required double? maxScrollExtent,
+    required double? pixels,
+    required double? viewportDimension,
     required AxisDirection axisDirection,
     required this.itemIndex,
   }) : super(
@@ -332,10 +332,10 @@ class FixedExtentMetrics extends FixedScrollMetrics {
     int? itemIndex,
   }) {
     return FixedExtentMetrics(
-      minScrollExtent: minScrollExtent ?? this.minScrollExtent,
-      maxScrollExtent: maxScrollExtent ?? this.maxScrollExtent,
-      pixels: pixels ?? this.pixels,
-      viewportDimension: viewportDimension ?? this.viewportDimension,
+      minScrollExtent: minScrollExtent ?? (hasContentDimensions ? this.minScrollExtent : null),
+      maxScrollExtent: maxScrollExtent ?? (hasContentDimensions ? this.maxScrollExtent : null),
+      pixels: pixels ?? (hasPixels ? this.pixels : null),
+      viewportDimension: viewportDimension ?? (hasViewportDimension ? this.viewportDimension : null),
       axisDirection: axisDirection ?? this.axisDirection,
       itemIndex: itemIndex ?? this.itemIndex,
     );
@@ -412,10 +412,10 @@ class _FixedExtentScrollPosition extends ScrollPositionWithSingleContext impleme
     int? itemIndex,
   }) {
     return FixedExtentMetrics(
-      minScrollExtent: minScrollExtent ?? this.minScrollExtent,
-      maxScrollExtent: maxScrollExtent ?? this.maxScrollExtent,
-      pixels: pixels ?? this.pixels,
-      viewportDimension: viewportDimension ?? this.viewportDimension,
+      minScrollExtent: minScrollExtent ?? (hasContentDimensions ? this.minScrollExtent : null),
+      maxScrollExtent: maxScrollExtent ?? (hasContentDimensions ? this.maxScrollExtent : null),
+      pixels: pixels ?? (hasPixels ? this.pixels : null),
+      viewportDimension: viewportDimension ?? (hasViewportDimension ? this.viewportDimension : null),
       axisDirection: axisDirection ?? this.axisDirection,
       itemIndex: itemIndex ?? this.itemIndex,
     );

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

@@ -706,10 +706,10 @@ class _InheritedNestedScrollView extends InheritedWidget {
 
 class _NestedScrollMetrics extends FixedScrollMetrics {
   _NestedScrollMetrics({
-    required double minScrollExtent,
-    required double maxScrollExtent,
-    required double pixels,
-    required double viewportDimension,
+    required double? minScrollExtent,
+    required double? maxScrollExtent,
+    required double? pixels,
+    required double? viewportDimension,
     required AxisDirection axisDirection,
     required this.minRange,
     required this.maxRange,
@@ -734,10 +734,10 @@ class _NestedScrollMetrics extends FixedScrollMetrics {
     double? correctionOffset,
   }) {
     return _NestedScrollMetrics(
-      minScrollExtent: minScrollExtent ?? this.minScrollExtent,
-      maxScrollExtent: maxScrollExtent ?? this.maxScrollExtent,
-      pixels: pixels ?? this.pixels,
-      viewportDimension: viewportDimension ?? this.viewportDimension,
+      minScrollExtent: minScrollExtent ?? (hasContentDimensions ? this.minScrollExtent : null),
+      maxScrollExtent: maxScrollExtent ?? (hasContentDimensions ? this.maxScrollExtent : null),
+      pixels: pixels ?? (hasPixels ? this.pixels : null),
+      viewportDimension: viewportDimension ?? (hasViewportDimension ? this.viewportDimension : null),
       axisDirection: axisDirection ?? this.axisDirection,
       minRange: minRange ?? this.minRange,
       maxRange: maxRange ?? this.maxRange,

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

@@ -262,10 +262,10 @@ class PageController extends ScrollController {
 class PageMetrics extends FixedScrollMetrics {
   /// Creates an immutable snapshot of values associated with a [PageView].
   PageMetrics({
-    required double minScrollExtent,
-    required double maxScrollExtent,
-    required double pixels,
-    required double viewportDimension,
+    required double? minScrollExtent,
+    required double? maxScrollExtent,
+    required double? pixels,
+    required double? viewportDimension,
     required AxisDirection axisDirection,
     required this.viewportFraction,
   }) : super(
@@ -286,10 +286,10 @@ class PageMetrics extends FixedScrollMetrics {
     double? viewportFraction,
   }) {
     return PageMetrics(
-      minScrollExtent: minScrollExtent ?? this.minScrollExtent,
-      maxScrollExtent: maxScrollExtent ?? this.maxScrollExtent,
-      pixels: pixels ?? this.pixels,
-      viewportDimension: viewportDimension ?? this.viewportDimension,
+      minScrollExtent: minScrollExtent ?? (hasContentDimensions ? this.minScrollExtent : null),
+      maxScrollExtent: maxScrollExtent ?? (hasContentDimensions ? this.maxScrollExtent : null),
+      pixels: pixels ?? (hasPixels ? this.pixels : null),
+      viewportDimension: viewportDimension ?? (hasViewportDimension ? this.viewportDimension : null),
       axisDirection: axisDirection ?? this.axisDirection,
       viewportFraction: viewportFraction ?? this.viewportFraction,
     );
@@ -441,10 +441,10 @@ class _PagePosition extends ScrollPositionWithSingleContext implements PageMetri
     double? viewportFraction,
   }) {
     return PageMetrics(
-      minScrollExtent: minScrollExtent ?? this.minScrollExtent,
-      maxScrollExtent: maxScrollExtent ?? this.maxScrollExtent,
-      pixels: pixels ?? this.pixels,
-      viewportDimension: viewportDimension ?? this.viewportDimension,
+      minScrollExtent: minScrollExtent ?? (hasContentDimensions ? this.minScrollExtent : null),
+      maxScrollExtent: maxScrollExtent ?? (hasContentDimensions ? this.maxScrollExtent : null),
+      pixels: pixels ?? (hasPixels ? this.pixels : null),
+      viewportDimension: viewportDimension ?? (hasViewportDimension ? this.viewportDimension : null),
       axisDirection: axisDirection ?? this.axisDirection,
       viewportFraction: viewportFraction ?? this.viewportFraction,
     );