Fix `CupertinoPicker`dark mode text color (#100310)

Improved code

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

@@ -281,11 +281,12 @@ class _CupertinoPickerState extends State<CupertinoPicker> {
 
   @override
   Widget build(BuildContext context) {
+    final TextStyle textStyle = CupertinoTheme.of(context).textTheme.pickerTextStyle;
     final Color? resolvedBackgroundColor = CupertinoDynamicColor.maybeResolve(widget.backgroundColor, context);
 
     assert(RenderListWheelViewport.defaultPerspective == _kDefaultPerspective);
     final Widget result = DefaultTextStyle(
-      style: CupertinoTheme.of(context).textTheme.pickerTextStyle,
+      style: textStyle.copyWith(color: CupertinoDynamicColor.maybeResolve(textStyle.color, context)),
       child: Stack(
         children: <Widget>[
           Positioned.fill(

packages/flutter/test/cupertino/picker_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -423,6 +424,46 @@ void main() {
     }, variant: const TargetPlatformVariant(<TargetPlatform>{ TargetPlatform.iOS,  TargetPlatform.macOS }));
   });
 
+  testWidgets('Picker adapts to MaterialApp dark mode', (WidgetTester tester) async {
+    Widget _buildCupertinoPicker(Brightness brightness) {
+      return MaterialApp(
+        theme: ThemeData(brightness: brightness),
+        home: Align(
+          alignment: Alignment.topLeft,
+          child: SizedBox(
+            height: 300.0,
+            width: 300.0,
+            child: CupertinoPicker(
+              itemExtent: 50.0,
+              onSelectedItemChanged: (_) { },
+              children: List<Widget>.generate(3, (int index) {
+                return SizedBox(
+                  height: 50.0,
+                  width: 300.0,
+                  child: Text(index.toString()),
+                );
+              }),
+            ),
+          ),
+        ),
+      );
+    }
+
+    // CupertinoPicker with light theme.
+    await tester.pumpWidget(_buildCupertinoPicker(Brightness.light));
+    RenderParagraph paragraph = tester.renderObject(find.text('1'));
+    expect(paragraph.text.style!.color, CupertinoColors.label);
+    // Text style should not return unresolved color.
+    expect(paragraph.text.style!.color.toString().contains('UNRESOLVED'), isFalse);
+
+    // CupertinoPicker with dark theme.
+    await tester.pumpWidget(_buildCupertinoPicker(Brightness.dark));
+    paragraph = tester.renderObject(find.text('1'));
+    expect(paragraph.text.style!.color, CupertinoColors.label);
+    // Text style should not return unresolved color.
+    expect(paragraph.text.style!.color.toString().contains('UNRESOLVED'), isFalse);
+  });
+
   group('CupertinoPickerDefaultSelectionOverlay', () {
     testWidgets('should be using directional decoration', (WidgetTester tester) async {
       await tester.pumpWidget(