Improvements to CircleAvatar text color (for #8895 codelab) (#8936)

* Improvements to CircleAvatar default color (for codelab)

* use a transparent white instead of a solid one

* Fix analyzer errors

* fix tests

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

@@ -7,6 +7,7 @@ import 'package:flutter/widgets.dart';
 
 import 'constants.dart';
 import 'theme.dart';
+import 'typography.dart';
 
 /// A circle that represents a user.
 ///
@@ -48,7 +49,8 @@ class CircleAvatar extends StatelessWidget {
     this.child,
     this.backgroundColor,
     this.backgroundImage,
-    this.radius: 20.0
+    this.foregroundColor,
+    this.radius: 20.0,
   }) : super(key: key);
 
   /// The widget below this widget in the tree.
@@ -59,8 +61,16 @@ class CircleAvatar extends StatelessWidget {
 
   /// The color with which to fill the circle. Changing the background
   /// color will cause the avatar to animate to the new color.
+  ///
+  /// If a background color is not specified, the theme's primary color is used.
   final Color backgroundColor;
 
+  /// The default text color for text in the circle.
+  ///
+  /// Falls back to white if a background color is specified, or the primary
+  /// text theme color otherwise.
+  final Color foregroundColor;
+
   /// The background image of the circle. Changing the background
   /// image will cause the avatar to animate to the new image.
   ///
@@ -76,13 +86,15 @@ class CircleAvatar extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final ThemeData theme = Theme.of(context);
-    final Color color = backgroundColor ?? theme.primaryColor;
+    final TextStyle textStyle = backgroundColor != null ?
+        new Typography(platform: theme.platform).white.title :
+        theme.primaryTextTheme.title;
     return new AnimatedContainer(
       width: radius * 2.0,
       height: radius * 2.0,
       duration: kThemeChangeDuration,
       decoration: new BoxDecoration(
-        backgroundColor: color,
+        backgroundColor: backgroundColor ?? theme.primaryColor,
         backgroundImage: backgroundImage != null ? new BackgroundImage(
           image: backgroundImage
         ) : null,
@@ -90,7 +102,7 @@ class CircleAvatar extends StatelessWidget {
       ),
       child: child != null ? new Center(
         child: new DefaultTextStyle(
-          style: theme.primaryTextTheme.title,
+          style: textStyle.copyWith(color: foregroundColor),
           child: child,
         )
       ) : null,

packages/flutter/test/material/circle_avatar_test.dart

@@ -3,24 +3,79 @@
 // found in the LICENSE file.
 
 import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
-  testWidgets('CircleAvatar test', (WidgetTester tester) async {
+  testWidgets('CircleAvatar with background color', (WidgetTester tester) async {
+    final Color backgroundColor = Colors.blue.shade400;
     await tester.pumpWidget(
       new Center(
         child: new CircleAvatar(
-          backgroundColor: Colors.blue[400],
+          backgroundColor: backgroundColor,
           radius: 50.0,
-          child: new Text('Z')
+          child: new Text('Z'),
-        )
+        ),
-      )
+      ),
     );
 
-    final RenderBox box = tester.renderObject(find.byType(CircleAvatar));
+    final RenderConstrainedBox box = tester.renderObject(find.byType(CircleAvatar));
     expect(box.size.width, equals(100.0));
     expect(box.size.height, equals(100.0));
+    final RenderDecoratedBox child = box.child;
+    final BoxDecoration decoration = child.decoration;
+    expect(decoration.backgroundColor, equals(backgroundColor));
 
-    expect(find.text('Z'), findsOneWidget);
+    final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
+    expect(paragraph.text.style.color, equals(Colors.white));
+  });
+
+  testWidgets('CircleAvatar with foreground color', (WidgetTester tester) async {
+    final Color foregroundColor = Colors.red.shade100;
+    await tester.pumpWidget(
+      new Center(
+        child: new CircleAvatar(
+          foregroundColor: foregroundColor,
+          child: new Text('Z'),
+        ),
+      ),
+    );
+
+    final ThemeData fallback = new ThemeData.fallback();
+
+    final RenderConstrainedBox box = tester.renderObject(find.byType(CircleAvatar));
+    expect(box.size.width, equals(40.0));
+    expect(box.size.height, equals(40.0));
+    final RenderDecoratedBox child = box.child;
+    final BoxDecoration decoration = child.decoration;
+    expect(decoration.backgroundColor, equals(fallback.primaryColor));
+
+    final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
+    expect(paragraph.text.style.color, equals(foregroundColor));
+  });
+
+  testWidgets('CircleAvatar with theme', (WidgetTester tester) async {
+    final ThemeData theme = new ThemeData(
+      primaryColor: Colors.grey.shade100,
+      primaryColorBrightness: Brightness.light,
+    );
+    await tester.pumpWidget(
+      new Theme(
+        data: theme,
+        child: new Center(
+          child: new CircleAvatar(
+            child: new Text('Z'),
+          ),
+        ),
+      ),
+    );
+
+    final RenderConstrainedBox box = tester.renderObject(find.byType(CircleAvatar));
+    final RenderDecoratedBox child = box.child;
+    final BoxDecoration decoration = child.decoration;
+    expect(decoration.backgroundColor, equals(theme.primaryColor));
+
+    final RenderParagraph paragraph = tester.renderObject(find.text('Z'));
+    expect(paragraph.text.style.color, equals(theme.primaryTextTheme.title.color));
   });
 }