barrierColor property in DialogTheme (#142490)

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

@@ -1327,7 +1327,8 @@ Widget _buildMaterialDialogTransitions(BuildContext context, Animation<double> a
 /// barrier will dismiss the dialog. It is `true` by default and can not be `null`.
 ///
 /// The `barrierColor` argument is used to specify the color of the modal
-/// barrier that darkens everything below the dialog. If `null` the default color
+/// barrier that darkens everything below the dialog. If `null` the `barrierColor`
+/// field from `DialogTheme` is used. If that is `null` the default color
 /// `Colors.black54` is used.
 ///
 /// The `useSafeArea` argument is used to indicate if the dialog should only
@@ -1428,7 +1429,7 @@ Future<T?> showDialog<T>({
   return Navigator.of(context, rootNavigator: useRootNavigator).push<T>(DialogRoute<T>(
     context: context,
     builder: builder,
-    barrierColor: barrierColor ?? Colors.black54,
+    barrierColor: barrierColor ?? Theme.of(context).dialogTheme.barrierColor ?? Colors.black54,
     barrierDismissible: barrierDismissible,
     barrierLabel: barrierLabel,
     useSafeArea: useSafeArea,

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

@@ -38,6 +38,7 @@ class DialogTheme with Diagnosticable {
     this.titleTextStyle,
     this.contentTextStyle,
     this.actionsPadding,
+    this.barrierColor,
   });
 
   /// Overrides the default value for [Dialog.backgroundColor].
@@ -72,6 +73,9 @@ class DialogTheme with Diagnosticable {
   /// Used to configure the [IconTheme] for the [AlertDialog.icon] widget.
   final Color? iconColor;
 
+  /// Overrides the default value for [barrierColor] in [showDialog].
+  final Color? barrierColor;
+
   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   DialogTheme copyWith({
@@ -85,6 +89,7 @@ class DialogTheme with Diagnosticable {
     TextStyle? titleTextStyle,
     TextStyle? contentTextStyle,
     EdgeInsetsGeometry? actionsPadding,
+    Color? barrierColor,
   }) {
     return DialogTheme(
       backgroundColor: backgroundColor ?? this.backgroundColor,
@@ -97,6 +102,7 @@ class DialogTheme with Diagnosticable {
       titleTextStyle: titleTextStyle ?? this.titleTextStyle,
       contentTextStyle: contentTextStyle ?? this.contentTextStyle,
       actionsPadding: actionsPadding ?? this.actionsPadding,
+      barrierColor: barrierColor ?? this.barrierColor,
     );
   }
 
@@ -123,6 +129,7 @@ class DialogTheme with Diagnosticable {
       titleTextStyle: TextStyle.lerp(a?.titleTextStyle, b?.titleTextStyle, t),
       contentTextStyle: TextStyle.lerp(a?.contentTextStyle, b?.contentTextStyle, t),
       actionsPadding: EdgeInsetsGeometry.lerp(a?.actionsPadding, b?.actionsPadding, t),
+      barrierColor: Color.lerp(a?.barrierColor, b?.barrierColor, t),
     );
   }
 
@@ -147,7 +154,8 @@ class DialogTheme with Diagnosticable {
         && other.iconColor == iconColor
         && other.titleTextStyle == titleTextStyle
         && other.contentTextStyle == contentTextStyle
-        && other.actionsPadding == actionsPadding;
+        && other.actionsPadding == actionsPadding
+        && other.barrierColor == barrierColor;
   }
 
   @override
@@ -163,5 +171,6 @@ class DialogTheme with Diagnosticable {
     properties.add(DiagnosticsProperty<TextStyle>('titleTextStyle', titleTextStyle, defaultValue: null));
     properties.add(DiagnosticsProperty<TextStyle>('contentTextStyle', contentTextStyle, defaultValue: null));
     properties.add(DiagnosticsProperty<EdgeInsetsGeometry>('actionsPadding', actionsPadding, defaultValue: null));
+    properties.add(ColorProperty('barrierColor', barrierColor));
   }
 }

packages/flutter/test/material/dialog_theme_test.dart

@@ -66,6 +66,7 @@ void main() {
       titleTextStyle: TextStyle(color: Color(0xffffffff)),
       contentTextStyle: TextStyle(color: Color(0xff000000)),
       actionsPadding: EdgeInsets.all(8.0),
+      barrierColor: Color(0xff000005),
     ).debugFillProperties(builder);
     final List<String> description = builder.properties
         .where((DiagnosticsNode n) => !n.isFiltered(DiagnosticLevel.info))
@@ -80,6 +81,7 @@ void main() {
       'titleTextStyle: TextStyle(inherit: true, color: Color(0xffffffff))',
       'contentTextStyle: TextStyle(inherit: true, color: Color(0xff000000))',
       'actionsPadding: EdgeInsets.all(8.0)',
+      'barrierColor: Color(0xff000005)',
     ]);
   });
 
@@ -499,4 +501,17 @@ void main() {
     final RenderParagraph content = _getTextRenderObject(tester, contentText);
     expect(content.text.style!.color, contentTextStyle.color);
   });
+
+  testWidgets('Custom barrierColor - Theme', (WidgetTester tester) async {
+    const Color barrierColor = Colors.blue;
+    const SimpleDialog dialog = SimpleDialog();
+    final ThemeData theme = ThemeData(dialogTheme: const DialogTheme(barrierColor: barrierColor));
+
+    await tester.pumpWidget(_appWithDialog(tester, dialog, theme: theme));
+    await tester.tap(find.text('X'));
+    await tester.pumpAndSettle();
+
+    final ModalBarrier modalBarrier = tester.widget(find.byType(ModalBarrier).last);
+    expect(modalBarrier.color, barrierColor);
+  });
 }