Remove `nullOk` parameter from Cupertino color resolution APIs (#68905)

* Remove nullOk from cupertino color resolution

* Add CupertinoDynamicColor.maybeResolveFrom

* Remove CupertinoDynamicColor.maybeResolveFrom again

packages/flutter/lib/src/cupertino/action_sheet.dart

@@ -450,14 +450,14 @@ class _CupertinoAlertRenderWidget extends RenderObjectWidget {
     assert(debugCheckHasMediaQuery(context));
     return _RenderCupertinoAlert(
       dividerThickness: _kDividerThickness / MediaQuery.of(context).devicePixelRatio,
-      dividerColor: CupertinoDynamicColor.resolve(_kButtonDividerColor, context)!,
+      dividerColor: CupertinoDynamicColor.resolve(_kButtonDividerColor, context),
     );
   }
 
   @override
   void updateRenderObject(BuildContext context, _RenderCupertinoAlert renderObject) {
     super.updateRenderObject(context, renderObject);
-    renderObject.dividerColor = CupertinoDynamicColor.resolve(_kButtonDividerColor, context)!;
+    renderObject.dividerColor = CupertinoDynamicColor.resolve(_kButtonDividerColor, context);
   }
 
   @override
@@ -1071,10 +1071,10 @@ class _CupertinoAlertActionsRenderWidget extends MultiChildRenderObjectWidget {
   RenderObject createRenderObject(BuildContext context) {
     return _RenderCupertinoAlertActions(
       dividerThickness: _dividerThickness,
-      dividerColor: CupertinoDynamicColor.resolve(_kButtonDividerColor, context)!,
+      dividerColor: CupertinoDynamicColor.resolve(_kButtonDividerColor, context),
       hasCancelButton: _hasCancelButton,
-      backgroundColor: CupertinoDynamicColor.resolve(_kBackgroundColor, context)!,
-      pressedColor: CupertinoDynamicColor.resolve(_kPressedColor, context)!,
+      backgroundColor: CupertinoDynamicColor.resolve(_kBackgroundColor, context),
+      pressedColor: CupertinoDynamicColor.resolve(_kPressedColor, context),
     );
   }
 
@@ -1082,10 +1082,10 @@ class _CupertinoAlertActionsRenderWidget extends MultiChildRenderObjectWidget {
   void updateRenderObject(BuildContext context, _RenderCupertinoAlertActions renderObject) {
     renderObject
       ..dividerThickness = _dividerThickness
-      ..dividerColor = CupertinoDynamicColor.resolve(_kButtonDividerColor, context)!
+      ..dividerColor = CupertinoDynamicColor.resolve(_kButtonDividerColor, context)
       ..hasCancelButton = _hasCancelButton
-      ..backgroundColor = CupertinoDynamicColor.resolve(_kBackgroundColor, context)!
-      ..pressedColor = CupertinoDynamicColor.resolve(_kPressedColor, context)!;
+      ..backgroundColor = CupertinoDynamicColor.resolve(_kBackgroundColor, context)
+      ..pressedColor = CupertinoDynamicColor.resolve(_kPressedColor, context);
   }
 }
 

packages/flutter/lib/src/cupertino/activity_indicator.dart

@@ -119,7 +119,7 @@ class _CupertinoActivityIndicatorState extends State<CupertinoActivityIndicator>
         painter: _CupertinoActivityIndicatorPainter(
           position: _controller,
           activeColor:
-              CupertinoDynamicColor.resolve(_kActiveTickColor, context)!,
+              CupertinoDynamicColor.resolve(_kActiveTickColor, context),
           radius: widget.radius,
           progress: widget.progress,
         ),

packages/flutter/lib/src/cupertino/app.dart

@@ -378,7 +378,7 @@ class _CupertinoAppState extends State<CupertinoApp> {
 
   WidgetsApp _buildWidgetApp(BuildContext context) {
     final CupertinoThemeData effectiveThemeData = CupertinoTheme.of(context);
-    final Color color = CupertinoDynamicColor.resolve(widget.color ?? effectiveThemeData.primaryColor, context)!;
+    final Color color = CupertinoDynamicColor.resolve(widget.color ?? effectiveThemeData.primaryColor, context);
 
     if (_usesRouter) {
       return WidgetsApp.router(

packages/flutter/lib/src/cupertino/bottom_tab_bar.dart

@@ -137,7 +137,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
   bool opaque(BuildContext context) {
     final Color backgroundColor =
         this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor;
-    return CupertinoDynamicColor.resolve(backgroundColor, context)!.alpha == 0xFF;
+    return CupertinoDynamicColor.resolve(backgroundColor, context).alpha == 0xFF;
   }
 
   @override
@@ -145,7 +145,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
     assert(debugCheckHasMediaQuery(context));
     final double bottomPadding = MediaQuery.of(context).padding.bottom;
 
-    final Color? backgroundColor = CupertinoDynamicColor.resolve(
+    final Color backgroundColor = CupertinoDynamicColor.resolve(
       this.backgroundColor ?? CupertinoTheme.of(context).barBackgroundColor,
       context,
     );
@@ -166,7 +166,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
         right: resolveBorderSide(border!.right),
       );
 
-    final Color? inactive = CupertinoDynamicColor.resolve(inactiveColor, context);
+    final Color inactive = CupertinoDynamicColor.resolve(inactiveColor, context);
     Widget result = DecoratedBox(
       decoration: BoxDecoration(
         border: resolvedBorder,
@@ -259,7 +259,7 @@ class CupertinoTabBar extends StatelessWidget implements PreferredSizeWidget {
     if (!active)
       return item;
 
-    final Color? activeColor = CupertinoDynamicColor.resolve(
+    final Color activeColor = CupertinoDynamicColor.resolve(
       this.activeColor ?? CupertinoTheme.of(context).primaryColor,
       context,
     );

packages/flutter/lib/src/cupertino/button.dart

@@ -214,9 +214,9 @@ class _CupertinoButtonState extends State<CupertinoButton> with SingleTickerProv
     final Color primaryColor = themeData.primaryColor;
     final Color? backgroundColor = widget.color == null
       ? (widget._filled ? primaryColor : null)
-      : CupertinoDynamicColor.resolve(widget.color, context);
+      : CupertinoDynamicColor.maybeResolve(widget.color, context);
 
-    final Color? foregroundColor = backgroundColor != null
+    final Color foregroundColor = backgroundColor != null
       ? themeData.primaryContrastingColor
       : enabled
         ? primaryColor

packages/flutter/lib/src/cupertino/colors.dart

@@ -876,6 +876,25 @@ class CupertinoDynamicColor extends Color with Diagnosticable {
   /// - has a [CupertinoUserInterfaceLevel] that indicates [CupertinoUserInterfaceLevelData.elevated].
   final Color darkHighContrastElevatedColor;
 
+  /// Resolves the given [Color] by calling [resolveFrom].
+  ///
+  /// If the given color is already a concrete [Color], it will be returned as is.
+  /// If the given color is a [CupertinoDynamicColor], but the given [BuildContext]
+  /// lacks the dependencies required to the color resolution, the default trait
+  /// value will be used ([Brightness.light] platform brightness, normal contrast,
+  /// [CupertinoUserInterfaceLevelData.base] elevation level).
+  ///
+  /// See also:
+  ///
+  ///  * [maybeResolve], which is similar to this function, but will allow a
+  ///    null `resolvable` color.
+  static Color resolve(Color resolvable, BuildContext context) {
+    assert(context != null);
+    return (resolvable is CupertinoDynamicColor)
+      ? resolvable.resolveFrom(context)
+      : resolvable;
+  }
+
   /// Resolves the given [Color] by calling [resolveFrom].
   ///
   /// If the given color is already a concrete [Color], it will be returned as is.
@@ -883,14 +902,18 @@ class CupertinoDynamicColor extends Color with Diagnosticable {
   /// If the given color is a [CupertinoDynamicColor], but the given [BuildContext]
   /// lacks the dependencies required to the color resolution, the default trait
   /// value will be used ([Brightness.light] platform brightness, normal contrast,
-  /// [CupertinoUserInterfaceLevelData.base] elevation level), unless [nullOk] is
-  /// set to false, in which case an exception will be thrown.
-  static Color? resolve(Color? resolvable, BuildContext context, { bool nullOk = true }) {
+  /// [CupertinoUserInterfaceLevelData.base] elevation level).
+  ///
+  /// See also:
+  ///
+  ///  * [resolve], which is similar to this function, but returns a
+  ///    non-nullable value, and does not allow a null `resolvable` color.
+  static Color? maybeResolve(Color? resolvable, BuildContext context) {
     if (resolvable == null)
       return null;
     assert(context != null);
     return (resolvable is CupertinoDynamicColor)
-      ? resolvable.resolveFrom(context, nullOk: nullOk)
+      ? resolvable.resolveFrom(context)
       : resolvable;
   }
 
@@ -921,15 +944,17 @@ class CupertinoDynamicColor extends Color with Diagnosticable {
   /// identical to this [CupertinoDynamicColor], except the effective color is
   /// changed to adapt to the given [BuildContext].
   ///
-  /// For example, if the given [BuildContext] indicates the widgets in the subtree
-  /// should be displayed in dark mode (the surrounding [CupertinoTheme]'s [CupertinoThemeData.brightness]
-  /// or [MediaQuery]'s [MediaQueryData.platformBrightness] is [Brightness.dark]),
-  /// with a high accessibility contrast (the surrounding [MediaQuery]'s [MediaQueryData.highContrast]
-  /// is `true`), and an elevated interface elevation (the surrounding [CupertinoUserInterfaceLevel]'s
-  /// `data` is [CupertinoUserInterfaceLevelData.elevated]), the resolved
+  /// For example, if the given [BuildContext] indicates the widgets in the
+  /// subtree should be displayed in dark mode (the surrounding
+  /// [CupertinoTheme]'s [CupertinoThemeData.brightness] or [MediaQuery]'s
+  /// [MediaQueryData.platformBrightness] is [Brightness.dark]), with a high
+  /// accessibility contrast (the surrounding [MediaQuery]'s
+  /// [MediaQueryData.highContrast] is `true`), and an elevated interface
+  /// elevation (the surrounding [CupertinoUserInterfaceLevel]'s `data` is
+  /// [CupertinoUserInterfaceLevelData.elevated]), the resolved
   /// [CupertinoDynamicColor] will be the same as this [CupertinoDynamicColor],
-  /// except its effective color will be the `darkHighContrastElevatedColor` variant
-  /// from the original [CupertinoDynamicColor].
+  /// except its effective color will be the `darkHighContrastElevatedColor`
+  /// variant from the original [CupertinoDynamicColor].
   ///
   /// Calling this function may create dependencies on the closest instance of some
   /// [InheritedWidget]s that enclose the given [BuildContext]. E.g., if [darkColor]
@@ -941,24 +966,19 @@ class CupertinoDynamicColor extends Color with Diagnosticable {
   /// If any of the required dependencies are missing from the given context, the
   /// default value of that trait will be used ([Brightness.light] platform
   /// brightness, normal contrast, [CupertinoUserInterfaceLevelData.base] elevation
-  /// level), unless [nullOk] is set to false, in which case an exception will be
-  /// thrown.
-  CupertinoDynamicColor resolveFrom(BuildContext context, { bool nullOk = true }) {
+  /// level).
+  CupertinoDynamicColor resolveFrom(BuildContext context) {
     Brightness brightness = Brightness.light;
     if (_isPlatformBrightnessDependent) {
-      brightness = nullOk
-          ? CupertinoTheme.maybeBrightnessOf(context) ?? Brightness.light
-          : CupertinoTheme.brightnessOf(context);
+      brightness =  CupertinoTheme.maybeBrightnessOf(context) ?? Brightness.light;
     }
     bool isHighContrastEnabled = false;
     if (_isHighContrastDependent) {
-      isHighContrastEnabled = nullOk
-          ? MediaQuery.maybeOf(context)?.highContrast ?? false
-          : MediaQuery.of(context).highContrast;
+      isHighContrastEnabled = MediaQuery.maybeOf(context)?.highContrast ?? false;
     }
 
     final CupertinoUserInterfaceLevelData level = _isInterfaceElevationDependent
-      ? CupertinoUserInterfaceLevel.of(context, nullOk: nullOk) ?? CupertinoUserInterfaceLevelData.base
+      ? CupertinoUserInterfaceLevel.maybeOf(context) ?? CupertinoUserInterfaceLevelData.base
       : CupertinoUserInterfaceLevelData.base;
 
     final Color resolved;

packages/flutter/lib/src/cupertino/date_picker.dart

@@ -2087,7 +2087,7 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
             child: Align(
               alignment: widget.alignment,
               child: Container(
-                color: CupertinoDynamicColor.resolve(widget.backgroundColor, context),
+                color: CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context),
                 width: totalWidth,
                 height: _kPickerHeight,
                 child: DefaultTextStyle(

packages/flutter/lib/src/cupertino/dialog.dart

@@ -390,7 +390,7 @@ class _CupertinoDialogRenderWidget extends RenderObjectWidget {
     return _RenderCupertinoDialog(
       dividerThickness: _kDividerThickness / MediaQuery.of(context).devicePixelRatio,
       isInAccessibilityMode: _isInAccessibilityMode(context),
-      dividerColor: CupertinoDynamicColor.resolve(CupertinoColors.separator, context)!,
+      dividerColor: CupertinoDynamicColor.resolve(CupertinoColors.separator, context),
     );
   }
 
@@ -398,7 +398,7 @@ class _CupertinoDialogRenderWidget extends RenderObjectWidget {
   void updateRenderObject(BuildContext context, _RenderCupertinoDialog renderObject) {
     renderObject
       ..isInAccessibilityMode = _isInAccessibilityMode(context)
-      ..dividerColor = CupertinoDynamicColor.resolve(CupertinoColors.separator, context)!;
+      ..dividerColor = CupertinoDynamicColor.resolve(CupertinoColors.separator, context);
   }
 
   @override
@@ -1269,9 +1269,9 @@ class _CupertinoDialogActionsRenderWidget extends MultiChildRenderObjectWidget {
         ? _kAccessibilityCupertinoDialogWidth
         : _kCupertinoDialogWidth,
       dividerThickness: _dividerThickness,
-      dialogColor: CupertinoDynamicColor.resolve(_kDialogColor, context)!,
-      dialogPressedColor: CupertinoDynamicColor.resolve(_kDialogPressedColor, context)!,
-      dividerColor: CupertinoDynamicColor.resolve(CupertinoColors.separator, context)!,
+      dialogColor: CupertinoDynamicColor.resolve(_kDialogColor, context),
+      dialogPressedColor: CupertinoDynamicColor.resolve(_kDialogPressedColor, context),
+      dividerColor: CupertinoDynamicColor.resolve(CupertinoColors.separator, context),
     );
   }
 
@@ -1282,9 +1282,9 @@ class _CupertinoDialogActionsRenderWidget extends MultiChildRenderObjectWidget {
         ? _kAccessibilityCupertinoDialogWidth
         : _kCupertinoDialogWidth
       ..dividerThickness = _dividerThickness
-      ..dialogColor = CupertinoDynamicColor.resolve(_kDialogColor, context)!
-      ..dialogPressedColor = CupertinoDynamicColor.resolve(_kDialogPressedColor, context)!
-      ..dividerColor = CupertinoDynamicColor.resolve(CupertinoColors.separator, context)!;
+      ..dialogColor = CupertinoDynamicColor.resolve(_kDialogColor, context)
+      ..dialogPressedColor = CupertinoDynamicColor.resolve(_kDialogPressedColor, context)
+      ..dividerColor = CupertinoDynamicColor.resolve(CupertinoColors.separator, context);
   }
 }
 

packages/flutter/lib/src/cupertino/icon_theme_data.dart

@@ -22,7 +22,7 @@ class CupertinoIconThemeData extends IconThemeData with Diagnosticable {
   /// Called by [IconTheme.of] to resolve [color] against the given [BuildContext].
   @override
   IconThemeData resolve(BuildContext context) {
-    final Color? resolvedColor = CupertinoDynamicColor.resolve(color, context);
+    final Color? resolvedColor = CupertinoDynamicColor.maybeResolve(color, context);
     return resolvedColor == color ? this : copyWith(color: resolvedColor);
   }
 

packages/flutter/lib/src/cupertino/interface_level.dart

@@ -57,14 +57,16 @@ class CupertinoUserInterfaceLevel extends InheritedWidget {
   /// You can use this function to query the user interface elevation level within
   /// the given [BuildContext]. When that information changes, your widget will
   /// be scheduled to be rebuilt, keeping your widget up-to-date.
-  static CupertinoUserInterfaceLevelData? of(BuildContext context, { bool nullOk = false }) {
+  ///
+  /// See also:
+  ///
+  ///  * [maybeOf], which is similar, but will return null if no
+  ///    [CupertinoUserInterfaceLevel] encloses the given context.
+  static CupertinoUserInterfaceLevelData of(BuildContext context) {
     assert(context != null);
-    assert(nullOk != null);
     final CupertinoUserInterfaceLevel? query = context.dependOnInheritedWidgetOfExactType<CupertinoUserInterfaceLevel>();
     if (query != null)
       return query._data;
-    if (nullOk)
-      return null;
     throw FlutterError(
       'CupertinoUserInterfaceLevel.of() called with a context that does not contain a CupertinoUserInterfaceLevel.\n'
       'No CupertinoUserInterfaceLevel ancestor could be found starting from the context that was passed '
@@ -76,6 +78,27 @@ class CupertinoUserInterfaceLevel extends InheritedWidget {
     );
   }
 
+  /// The data from the closest instance of this class that encloses the given
+  /// context, if there is one.
+  ///
+  /// Returns null if no [CupertinoUserInterfaceLevel] encloses the given context.
+  ///
+  /// You can use this function to query the user interface elevation level within
+  /// the given [BuildContext]. When that information changes, your widget will
+  /// be scheduled to be rebuilt, keeping your widget up-to-date.
+  ///
+  /// See also:
+  ///
+  ///  * [of], which is similar, but will throw an exception if no
+  ///    [CupertinoUserInterfaceLevel] encloses the given context.
+  static CupertinoUserInterfaceLevelData? maybeOf(BuildContext context) {
+    assert(context != null);
+    final CupertinoUserInterfaceLevel? query = context.dependOnInheritedWidgetOfExactType<CupertinoUserInterfaceLevel>();
+    if (query != null)
+      return query._data;
+    return null;
+  }
+
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);

packages/flutter/lib/src/cupertino/nav_bar.dart

@@ -399,7 +399,7 @@ class CupertinoNavigationBar extends StatefulWidget implements ObstructingPrefer
   /// True if the navigation bar's background color has no transparency.
   @override
   bool shouldFullyObstruct(BuildContext context) {
-    final Color backgroundColor = CupertinoDynamicColor.resolve(this.backgroundColor, context)
+    final Color backgroundColor = CupertinoDynamicColor.maybeResolve(this.backgroundColor, context)
                                ?? CupertinoTheme.of(context).barBackgroundColor;
     return backgroundColor.alpha == 0xFF;
   }
@@ -430,7 +430,7 @@ class _CupertinoNavigationBarState extends State<CupertinoNavigationBar> {
   @override
   Widget build(BuildContext context) {
     final Color backgroundColor =
-      CupertinoDynamicColor.resolve(widget.backgroundColor, context) ?? CupertinoTheme.of(context).barBackgroundColor;
+      CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context) ?? CupertinoTheme.of(context).barBackgroundColor;
 
     final _NavigationBarStaticComponents components = _NavigationBarStaticComponents(
       keys: keys,
@@ -459,7 +459,7 @@ class _CupertinoNavigationBarState extends State<CupertinoNavigationBar> {
       ),
     );
 
-    final Color? actionsForegroundColor = CupertinoDynamicColor.resolve(
+    final Color? actionsForegroundColor = CupertinoDynamicColor.maybeResolve(
       widget.actionsForegroundColor,
       context,
     );
@@ -691,7 +691,7 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
   @override
   Widget build(BuildContext context) {
     // Lint ignore to maintain backward compatibility.
-    final Color actionsForegroundColor = CupertinoDynamicColor.resolve(widget.actionsForegroundColor, context)
+    final Color actionsForegroundColor = CupertinoDynamicColor.maybeResolve(widget.actionsForegroundColor, context)
                                       ?? CupertinoTheme.of(context).primaryColor;
 
     final _NavigationBarStaticComponents components = _NavigationBarStaticComponents(
@@ -720,7 +720,7 @@ class _CupertinoSliverNavigationBarState extends State<CupertinoSliverNavigation
             keys: keys,
             components: components,
             userMiddle: widget.middle,
-            backgroundColor: CupertinoDynamicColor.resolve(widget.backgroundColor, context) ?? CupertinoTheme.of(context).barBackgroundColor,
+            backgroundColor: CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context) ?? CupertinoTheme.of(context).barBackgroundColor,
             brightness: widget.brightness,
             border: widget.border,
             padding: widget.padding,
@@ -789,7 +789,7 @@ class _LargeTitleNavigationBarSliverDelegate
 
     final Widget navBar = _wrapWithBackground(
       border: border,
-      backgroundColor: CupertinoDynamicColor.resolve(backgroundColor, context)!,
+      backgroundColor: CupertinoDynamicColor.resolve(backgroundColor, context),
       brightness: brightness,
       child: DefaultTextStyle(
         style: CupertinoTheme.of(context).textTheme.textStyle,
@@ -1325,7 +1325,7 @@ class CupertinoNavigationBarBackButton extends StatelessWidget {
 
     TextStyle actionTextStyle = CupertinoTheme.of(context).textTheme.navActionTextStyle;
     if (color != null) {
-      actionTextStyle = actionTextStyle.copyWith(color: CupertinoDynamicColor.resolve(color, context));
+      actionTextStyle = actionTextStyle.copyWith(color: CupertinoDynamicColor.maybeResolve(color, context));
     }
 
     return CupertinoButton(

packages/flutter/lib/src/cupertino/page_scaffold.dart

@@ -157,7 +157,7 @@ class _CupertinoPageScaffoldState extends State<CupertinoPageScaffold> {
 
     return DecoratedBox(
       decoration: BoxDecoration(
-        color: CupertinoDynamicColor.resolve(widget.backgroundColor, context)
+        color: CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context)
             ?? CupertinoTheme.of(context).scaffoldBackgroundColor,
       ),
       child: Stack(

packages/flutter/lib/src/cupertino/picker.dart

@@ -278,7 +278,7 @@ class _CupertinoPickerState extends State<CupertinoPicker> {
 
   @override
   Widget build(BuildContext context) {
-    final Color? resolvedBackgroundColor = CupertinoDynamicColor.resolve(widget.backgroundColor, context);
+    final Color? resolvedBackgroundColor = CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context);
 
     final Widget result = DefaultTextStyle(
       style: CupertinoTheme.of(context).textTheme.pickerTextStyle,

packages/flutter/lib/src/cupertino/route.dart

@@ -1145,7 +1145,7 @@ Future<T?> showCupertinoDialog<T>({
     context: context,
     barrierDismissible: barrierDismissible,
     barrierLabel: CupertinoLocalizations.of(context).modalBarrierDismissLabel,
-    barrierColor: CupertinoDynamicColor.resolve(_kModalBarrierColor, context)!,
+    barrierColor: CupertinoDynamicColor.resolve(_kModalBarrierColor, context),
     // This transition duration was eyeballed comparing with iOS
     transitionDuration: const Duration(milliseconds: 250),
     pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {

packages/flutter/lib/src/cupertino/scrollbar.dart

@@ -284,7 +284,7 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
     } else {
       _painter!
         ..textDirection = Directionality.of(context)
-        ..color = CupertinoDynamicColor.resolve(_kScrollbarColor, context)!
+        ..color = CupertinoDynamicColor.resolve(_kScrollbarColor, context)
         ..padding = MediaQuery.of(context).padding;
     }
     _triggerScrollbar();
@@ -308,7 +308,7 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
   /// Returns a [ScrollbarPainter] visually styled like the iOS scrollbar.
   ScrollbarPainter _buildCupertinoScrollbarPainter(BuildContext context) {
     return ScrollbarPainter(
-      color: CupertinoDynamicColor.resolve(_kScrollbarColor, context)!,
+      color: CupertinoDynamicColor.resolve(_kScrollbarColor, context),
       textDirection: Directionality.of(context),
       thickness: _thickness,
       fadeoutOpacityAnimation: _fadeoutOpacityAnimation,

packages/flutter/lib/src/cupertino/slider.dart

@@ -243,7 +243,7 @@ class _CupertinoSliderState extends State<CupertinoSlider> with TickerProviderSt
       activeColor: CupertinoDynamicColor.resolve(
         widget.activeColor ?? CupertinoTheme.of(context).primaryColor,
         context,
-      )!,
+      ),
       thumbColor: widget.thumbColor,
       onChanged: widget.onChanged != null ? _handleChanged : null,
       onChangeStart: widget.onChangeStart != null ? _handleDragStart : null,
@@ -282,8 +282,8 @@ class _CupertinoSliderRenderObjectWidget extends LeafRenderObjectWidget {
       value: value,
       divisions: divisions,
       activeColor: activeColor,
-      thumbColor: CupertinoDynamicColor.resolve(thumbColor, context)!,
-      trackColor: CupertinoDynamicColor.resolve(CupertinoColors.systemFill, context)!,
+      thumbColor: CupertinoDynamicColor.resolve(thumbColor, context),
+      trackColor: CupertinoDynamicColor.resolve(CupertinoColors.systemFill, context),
       onChanged: onChanged,
       onChangeStart: onChangeStart,
       onChangeEnd: onChangeEnd,
@@ -299,8 +299,8 @@ class _CupertinoSliderRenderObjectWidget extends LeafRenderObjectWidget {
       ..value = value
       ..divisions = divisions
       ..activeColor = activeColor
-      ..thumbColor = CupertinoDynamicColor.resolve(thumbColor, context)!
-      ..trackColor = CupertinoDynamicColor.resolve(CupertinoColors.systemFill, context)!
+      ..thumbColor = CupertinoDynamicColor.resolve(thumbColor, context)
+      ..trackColor = CupertinoDynamicColor.resolve(CupertinoColors.systemFill, context)
       ..onChanged = onChanged
       ..onChangeStart = onChangeStart
       ..onChangeEnd = onChangeEnd

packages/flutter/lib/src/cupertino/sliding_segmented_control.dart

@@ -483,7 +483,7 @@ class _SegmentedControlRenderWidget<T> extends MultiChildRenderObjectWidget {
   RenderObject createRenderObject(BuildContext context) {
     return _RenderSegmentedControl<T>(
       selectedIndex: selectedIndex,
-      thumbColor: CupertinoDynamicColor.resolve(thumbColor, context),
+      thumbColor: CupertinoDynamicColor.maybeResolve(thumbColor, context),
       state: state,
     );
   }
@@ -491,7 +491,7 @@ class _SegmentedControlRenderWidget<T> extends MultiChildRenderObjectWidget {
   @override
   void updateRenderObject(BuildContext context, _RenderSegmentedControl<T> renderObject) {
     renderObject
-      ..thumbColor = CupertinoDynamicColor.resolve(thumbColor, context)
+      ..thumbColor = CupertinoDynamicColor.maybeResolve(thumbColor, context)
       ..guardedSetHighlightedIndex(selectedIndex);
   }
 }

packages/flutter/lib/src/cupertino/switch.dart

@@ -299,8 +299,8 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
         activeColor: CupertinoDynamicColor.resolve(
           widget.activeColor ?? CupertinoColors.systemGreen,
           context,
-        )!,
-        trackColor: CupertinoDynamicColor.resolve(widget.trackColor ?? CupertinoColors.secondarySystemFill, context)!,
+        ),
+        trackColor: CupertinoDynamicColor.resolve(widget.trackColor ?? CupertinoColors.secondarySystemFill, context),
         onChanged: widget.onChanged,
         textDirection: Directionality.of(context),
         state: this,

packages/flutter/lib/src/cupertino/tab_scaffold.dart

@@ -440,7 +440,7 @@ class _CupertinoTabScaffoldState extends State<CupertinoTabScaffold> with Restor
 
     return DecoratedBox(
       decoration: BoxDecoration(
-        color: CupertinoDynamicColor.resolve(widget.backgroundColor, context)
+        color: CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context)
             ?? CupertinoTheme.of(context).scaffoldBackgroundColor,
       ),
       child: Stack(

packages/flutter/lib/src/cupertino/text_field.dart

@@ -888,24 +888,24 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with Restoratio
     final CupertinoThemeData themeData = CupertinoTheme.of(context);
 
     final TextStyle? resolvedStyle = widget.style?.copyWith(
-      color: CupertinoDynamicColor.resolve(widget.style?.color, context),
-      backgroundColor: CupertinoDynamicColor.resolve(widget.style?.backgroundColor, context),
+      color: CupertinoDynamicColor.maybeResolve(widget.style?.color, context),
+      backgroundColor: CupertinoDynamicColor.maybeResolve(widget.style?.backgroundColor, context),
     );
 
     final TextStyle textStyle = themeData.textTheme.textStyle.merge(resolvedStyle);
 
     final TextStyle? resolvedPlaceholderStyle = widget.placeholderStyle?.copyWith(
-      color: CupertinoDynamicColor.resolve(widget.placeholderStyle?.color, context),
-      backgroundColor: CupertinoDynamicColor.resolve(widget.placeholderStyle?.backgroundColor, context),
+      color: CupertinoDynamicColor.maybeResolve(widget.placeholderStyle?.color, context),
+      backgroundColor: CupertinoDynamicColor.maybeResolve(widget.placeholderStyle?.backgroundColor, context),
     );
 
     final TextStyle placeholderStyle = textStyle.merge(resolvedPlaceholderStyle);
 
     final Brightness keyboardAppearance = widget.keyboardAppearance ?? CupertinoTheme.brightnessOf(context);
-    final Color cursorColor = CupertinoDynamicColor.resolve(widget.cursorColor, context) ?? themeData.primaryColor;
-    final Color? disabledColor = CupertinoDynamicColor.resolve(_kDisabledBackground, context);
+    final Color cursorColor = CupertinoDynamicColor.maybeResolve(widget.cursorColor, context) ?? themeData.primaryColor;
+    final Color disabledColor = CupertinoDynamicColor.resolve(_kDisabledBackground, context);
 
-    final Color? decorationColor = CupertinoDynamicColor.resolve(widget.decoration?.color, context);
+    final Color? decorationColor = CupertinoDynamicColor.maybeResolve(widget.decoration?.color, context);
 
     final BoxBorder? border = widget.decoration?.border;
     Border? resolvedBorder = border as Border?;
@@ -978,7 +978,7 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with Restoratio
             cursorOffset: cursorOffset,
             paintCursorAboveText: true,
             autocorrectionTextRectColor: selectionColor,
-            backgroundCursorColor: CupertinoDynamicColor.resolve(CupertinoColors.inactiveGray, context)!,
+            backgroundCursorColor: CupertinoDynamicColor.resolve(CupertinoColors.inactiveGray, context),
             selectionHeightStyle: widget.selectionHeightStyle,
             selectionWidthStyle: widget.selectionWidthStyle,
             scrollPadding: widget.scrollPadding,

packages/flutter/lib/src/cupertino/text_theme.dart

@@ -101,12 +101,12 @@ const TextStyle _kDefaultDateTimePickerTextStyle = TextStyle(
   color: CupertinoColors.label,
 );
 
-TextStyle? _resolveTextStyle(TextStyle? style, BuildContext context, bool nullOk) {
+TextStyle? _resolveTextStyle(TextStyle? style, BuildContext context) {
   // This does not resolve the shadow color, foreground, background, etc.
   return style?.copyWith(
-    color: CupertinoDynamicColor.resolve(style.color, context, nullOk: nullOk),
-    backgroundColor: CupertinoDynamicColor.resolve(style.backgroundColor, context, nullOk: nullOk),
-    decorationColor: CupertinoDynamicColor.resolve(style.decorationColor, context, nullOk: nullOk),
+    color: CupertinoDynamicColor.maybeResolve(style.color, context),
+    backgroundColor: CupertinoDynamicColor.maybeResolve(style.backgroundColor, context),
+    decorationColor: CupertinoDynamicColor.maybeResolve(style.decorationColor, context),
   );
 }
 
@@ -206,22 +206,23 @@ class CupertinoTextThemeData with Diagnosticable {
   /// Returns a copy of the current [CupertinoTextThemeData] with all the colors
   /// resolved against the given [BuildContext].
   ///
-  /// Throws an exception if any of the [InheritedWidget]s required to resolve
-  /// this [CupertinoTextThemeData] is not found in [context], unless [nullOk] is
-  /// set to true, in which case [CupertinoDynamicColor]s that fail to resolve will
-  /// be used as-is.
-  CupertinoTextThemeData resolveFrom(BuildContext context, { bool nullOk = false }) {
+  /// If any of the [InheritedWidget]s required to resolve this
+  /// [CupertinoTextThemeData] is not found in [context], any unresolved
+  /// [CupertinoDynamicColor]s will use the default trait value
+  /// ([Brightness.light] platform brightness, normal contrast,
+  /// [CupertinoUserInterfaceLevelData.base] elevation level).
+  CupertinoTextThemeData resolveFrom(BuildContext context) {
     return CupertinoTextThemeData._raw(
-      _defaults.resolveFrom(context, nullOk),
-      CupertinoDynamicColor.resolve(_primaryColor, context, nullOk: nullOk),
-      _resolveTextStyle(_textStyle, context, nullOk),
-      _resolveTextStyle(_actionTextStyle, context, nullOk),
-      _resolveTextStyle(_tabLabelTextStyle, context, nullOk),
-      _resolveTextStyle(_navTitleTextStyle, context, nullOk),
-      _resolveTextStyle(_navLargeTitleTextStyle, context, nullOk),
-      _resolveTextStyle(_navActionTextStyle, context, nullOk),
-      _resolveTextStyle(_pickerTextStyle, context, nullOk),
-      _resolveTextStyle(_dateTimePickerTextStyle, context, nullOk),
+      _defaults.resolveFrom(context),
+      CupertinoDynamicColor.maybeResolve(_primaryColor, context),
+      _resolveTextStyle(_textStyle, context),
+      _resolveTextStyle(_actionTextStyle, context),
+      _resolveTextStyle(_tabLabelTextStyle, context),
+      _resolveTextStyle(_navTitleTextStyle, context),
+      _resolveTextStyle(_navLargeTitleTextStyle, context),
+      _resolveTextStyle(_navActionTextStyle, context),
+      _resolveTextStyle(_pickerTextStyle, context),
+      _resolveTextStyle(_dateTimePickerTextStyle, context),
     );
   }
 
@@ -300,9 +301,9 @@ class _TextThemeDefaultsBuilder {
   TextStyle actionTextStyle({ Color? primaryColor }) => _kDefaultActionTextStyle.copyWith(color: primaryColor);
   TextStyle navActionTextStyle({ Color? primaryColor }) => actionTextStyle(primaryColor: primaryColor);
 
-  _TextThemeDefaultsBuilder resolveFrom(BuildContext context, bool nullOk) {
-    final Color resolvedLabelColor = CupertinoDynamicColor.resolve(labelColor, context, nullOk: nullOk)!;
-    final Color resolvedInactiveGray = CupertinoDynamicColor.resolve(inactiveGrayColor, context, nullOk: nullOk)!;
+  _TextThemeDefaultsBuilder resolveFrom(BuildContext context) {
+    final Color resolvedLabelColor = CupertinoDynamicColor.resolve(labelColor, context);
+    final Color resolvedInactiveGray = CupertinoDynamicColor.resolve(inactiveGrayColor, context);
     return resolvedLabelColor == labelColor && resolvedInactiveGray == CupertinoColors.inactiveGray
       ? this
       : _TextThemeDefaultsBuilder(resolvedLabelColor, resolvedInactiveGray);

packages/flutter/lib/src/cupertino/theme.dart

@@ -68,7 +68,7 @@ class CupertinoTheme extends StatelessWidget {
   /// given [BuildContext] on a best-effort basis.
   static CupertinoThemeData of(BuildContext context) {
     final _InheritedCupertinoTheme? inheritedTheme = context.dependOnInheritedWidgetOfExactType<_InheritedCupertinoTheme>();
-    return (inheritedTheme?.theme.data ?? const CupertinoThemeData()).resolveFrom(context, nullOk: true);
+    return (inheritedTheme?.theme.data ?? const CupertinoThemeData()).resolveFrom(context);
   }
 
   /// Retrieves the [Brightness] to use for descendant Cupertino widgets, based
@@ -256,17 +256,17 @@ class CupertinoThemeData extends NoDefaultCupertinoThemeData with Diagnosticable
   }
 
   @override
-  CupertinoThemeData resolveFrom(BuildContext context, { bool nullOk = false }) {
-    Color? convertColor(Color? color) => CupertinoDynamicColor.resolve(color, context, nullOk: nullOk);
+  CupertinoThemeData resolveFrom(BuildContext context) {
+    Color? convertColor(Color? color) => CupertinoDynamicColor.maybeResolve(color, context);
 
     return CupertinoThemeData._rawWithDefaults(
       brightness,
       convertColor(super.primaryColor),
       convertColor(super.primaryContrastingColor),
-      super.textTheme?.resolveFrom(context, nullOk: nullOk),
+      super.textTheme?.resolveFrom(context),
       convertColor(super.barBackgroundColor),
       convertColor(super.scaffoldBackgroundColor),
-      _defaults.resolveFrom(context, super.textTheme == null, nullOk: nullOk),
+      _defaults.resolveFrom(context, super.textTheme == null),
     );
   }
 
@@ -406,14 +406,14 @@ class NoDefaultCupertinoThemeData {
   /// Called by [CupertinoTheme.of] to resolve colors defined in the retrieved
   /// [CupertinoThemeData].
   @protected
-  NoDefaultCupertinoThemeData resolveFrom(BuildContext context, { bool nullOk = false }) {
-    Color? convertColor(Color? color) => CupertinoDynamicColor.resolve(color, context, nullOk: nullOk);
+  NoDefaultCupertinoThemeData resolveFrom(BuildContext context) {
+    Color? convertColor(Color? color) => CupertinoDynamicColor.maybeResolve(color, context);
 
     return NoDefaultCupertinoThemeData(
       brightness: brightness,
       primaryColor: convertColor(primaryColor),
       primaryContrastingColor: convertColor(primaryContrastingColor),
-      textTheme: textTheme?.resolveFrom(context, nullOk: nullOk),
+      textTheme: textTheme?.resolveFrom(context),
       barBackgroundColor: convertColor(barBackgroundColor),
       scaffoldBackgroundColor: convertColor(scaffoldBackgroundColor),
     );
@@ -462,9 +462,8 @@ class _CupertinoThemeDefaults {
   final Color scaffoldBackgroundColor;
   final _CupertinoTextThemeDefaults textThemeDefaults;
 
-  _CupertinoThemeDefaults resolveFrom(BuildContext context, bool resolveTextTheme, { required bool nullOk }) {
-    assert(nullOk != null);
-    Color convertColor(Color color) => CupertinoDynamicColor.resolve(color, context, nullOk: nullOk)!;
+  _CupertinoThemeDefaults resolveFrom(BuildContext context, bool resolveTextTheme) {
+    Color convertColor(Color color) => CupertinoDynamicColor.resolve(color, context);
 
     return _CupertinoThemeDefaults(
       brightness,
@@ -472,7 +471,7 @@ class _CupertinoThemeDefaults {
       convertColor(primaryContrastingColor),
       convertColor(barBackgroundColor),
       convertColor(scaffoldBackgroundColor),
-      resolveTextTheme ? textThemeDefaults.resolveFrom(context, nullOk: nullOk) : textThemeDefaults,
+      resolveTextTheme ? textThemeDefaults.resolveFrom(context) : textThemeDefaults,
     );
   }
 }
@@ -487,10 +486,10 @@ class _CupertinoTextThemeDefaults {
   final Color labelColor;
   final Color inactiveGray;
 
-  _CupertinoTextThemeDefaults resolveFrom(BuildContext context, { required bool nullOk }) {
+  _CupertinoTextThemeDefaults resolveFrom(BuildContext context) {
     return _CupertinoTextThemeDefaults(
-      CupertinoDynamicColor.resolve(labelColor, context, nullOk: nullOk)!,
-      CupertinoDynamicColor.resolve(inactiveGray, context, nullOk: nullOk)!,
+      CupertinoDynamicColor.resolve(labelColor, context),
+      CupertinoDynamicColor.resolve(inactiveGray, context),
     );
   }
 

packages/flutter/lib/src/material/theme_data.dart

@@ -1849,12 +1849,12 @@ class MaterialBasedCupertinoThemeData extends CupertinoThemeData {
   }
 
   @override
-  CupertinoThemeData resolveFrom(BuildContext context, { bool nullOk = false }) {
+  CupertinoThemeData resolveFrom(BuildContext context) {
     // Only the cupertino override theme part will be resolved.
     // If the color comes from the material theme it's not resolved.
     return MaterialBasedCupertinoThemeData._(
       _materialTheme,
-      _cupertinoOverrideTheme.resolveFrom(context, nullOk: nullOk),
+      _cupertinoOverrideTheme.resolveFrom(context),
     );
   }
 }

packages/flutter/test/cupertino/colors_test.dart

@@ -19,7 +19,7 @@ class DependentWidget extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final Color resolved = CupertinoDynamicColor.resolve(color, context, nullOk: false)!;
+    final Color resolved = CupertinoDynamicColor.resolve(color, context);
     return DecoratedBox(
       decoration: BoxDecoration(color: resolved),
       child: const SizedBox.expand(),
@@ -165,7 +165,7 @@ void main() {
   });
 
   test('can resolve null color', () {
-    expect(CupertinoDynamicColor.resolve(null, _NullElement.instance), isNull);
+    expect(CupertinoDynamicColor.maybeResolve(null, _NullElement.instance), isNull);
   });
 
   test('withVibrancy constructor creates colors that may depend on vibrancy', () {
@@ -280,10 +280,6 @@ void main() {
       expect(tester.takeException(), null);
       expect(find.byType(DependentWidget), paints..rect(color: color0));
       expect(find.byType(DependentWidget), isNot(paints..rect(color: color1)));
-
-      // Asserts when the required dependency is missing.
-      await tester.pumpWidget(const DependentWidget(color: contrastDependentColor1));
-      expect(tester.takeException()?.toString(), contains('No MediaQuery widget ancestor found'));
   });
 
   testWidgets(
@@ -312,10 +308,6 @@ void main() {
       expect(tester.takeException(), null);
       expect(find.byType(DependentWidget), paints..rect(color: color0));
       expect(find.byType(DependentWidget), isNot(paints..rect(color: color1)));
-
-      // Asserts when the required dependency is missing.
-      await tester.pumpWidget(const DependentWidget(color: elevationDependentColor1));
-      expect(tester.takeException()?.toString(), contains('does not contain a CupertinoUserInterfaceLevel'));
   });
 
   testWidgets('Dynamic color with all 3 dependencies works', (WidgetTester tester) async {