[RefreshIndicator] adds strokeWidth parameter to RefreshIndicator (#53344)

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

@@ -106,9 +106,11 @@ class RefreshIndicator extends StatefulWidget {
     this.notificationPredicate = defaultScrollNotificationPredicate,
     this.semanticsLabel,
     this.semanticsValue,
+    this.strokeWidth = 2.0
   }) : assert(child != null),
        assert(onRefresh != null),
        assert(notificationPredicate != null),
+       assert(strokeWidth != null),
        super(key: key);
 
   /// The widget below this widget in the tree.
@@ -153,6 +155,11 @@ class RefreshIndicator extends StatefulWidget {
   /// {@macro flutter.material.progressIndicator.semanticsValue}
   final String semanticsValue;
 
+  /// Defines `strokeWidth` for `RefreshIndicator`.
+  ///
+  /// By default, the value of `strokeWidth` is 2.0 pixels.
+  final double strokeWidth;
+
   @override
   RefreshIndicatorState createState() => RefreshIndicatorState();
 }
@@ -462,6 +469,7 @@ class RefreshIndicatorState extends State<RefreshIndicator> with TickerProviderS
                       value: showIndeterminateIndicator ? null : _value.value,
                       valueColor: _valueColor,
                       backgroundColor: widget.backgroundColor,
+                      strokeWidth: widget.strokeWidth,
                     );
                   },
                 ),

packages/flutter/test/material/refresh_indicator_test.dart

@@ -455,4 +455,77 @@ void main() {
 
     expect(layoutCount, 1);
   });
-}
\ No newline at end of file
+
+  testWidgets('strokeWidth cannot be null in RefreshIndicator', (WidgetTester tester) async {
+    try {
+      await tester.pumpWidget(
+          MaterialApp(
+            home: RefreshIndicator(
+              onRefresh: () async {},
+              strokeWidth: null,
+              child: ListView(
+                physics: const AlwaysScrollableScrollPhysics(),
+                children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
+                  return SizedBox(
+                    height: 200.0,
+                    child: Text(item),
+                  );
+                }).toList(),
+              ),
+            ),
+          )
+      );
+    } on AssertionError catch(_) {
+      return;
+    }
+    fail('The assertion was not thrown when strokeWidth was null');
+  });
+
+  testWidgets('RefreshIndicator responds to strokeWidth', (WidgetTester tester) async {
+    await tester.pumpWidget(
+        MaterialApp(
+          home: RefreshIndicator(
+            onRefresh: () async {},
+            child: ListView(
+              physics: const AlwaysScrollableScrollPhysics(),
+              children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
+                return SizedBox(
+                  height: 200.0,
+                  child: Text(item),
+                );
+              }).toList(),
+            ),
+          ),
+        )
+    );
+
+    //By default the value of strokeWidth is 2.0
+    expect(
+        tester.widget<RefreshIndicator>(find.byType(RefreshIndicator)).strokeWidth,
+        2.0,
+    );
+
+    await tester.pumpWidget(
+        MaterialApp(
+          home: RefreshIndicator(
+            onRefresh: () async {},
+            strokeWidth: 4.0,
+            child: ListView(
+              physics: const AlwaysScrollableScrollPhysics(),
+              children: <String>['A', 'B', 'C', 'D', 'E', 'F'].map<Widget>((String item) {
+                return SizedBox(
+                  height: 200.0,
+                  child: Text(item),
+                );
+              }).toList(),
+            ),
+          ),
+        )
+    );
+
+    expect(
+        tester.widget<RefreshIndicator>(find.byType(RefreshIndicator)).strokeWidth,
+        4.0,
+    );
+  });
+}