RaisedButton's background color does not change after setting ThemeData's primaryswatch property - flutter

Question

Below is a clean Flutter example with a RaisedButton.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
RaisedButton(
child: Text('test'),
onPressed: () {},
)
],
),
),
);
}
}
Snippet from theme_data.dart
// Used as the default color (fill color) for RaisedButtons. Computing the
// default for ButtonThemeData for the sake of backwards compatibility.
buttonColor ??= isDark ? primarySwatch[600] : Colors.grey[300];
Snippet from material_button.dart
/// The button's fill color, displayed by its [Material], while it
/// is in its default (unpressed, [enabled]) state.
///
/// The default fill color is the theme's button color, [ThemeData.buttonColor].
///
/// See also:
///
/// * [disabledColor] - the fill color of the button when the button is disabled.
final Color color;
Based on the above, I assume the RaisedButton will have a blueish background color since the buttonColor will be inferred from primarySwatch. Instead, the RaisedButton has a greyish background color.
I know I can set the buttonColor parameter directly via ThemeData but since the source code states that buttonColor will be inferred from primarySwatch, I'm just curious why it did not work. What did I miss?

Answer 1

Your answer is in the code you quoted:
buttonColor ??= isDark ? primarySwatch[600] : Colors.grey[300];
On that same file (theme_data.dart) you can see that isDark is defined as:
final bool isDark = brightness == Brightness.dark;
Since your theme isn't defined as Brightness.dark the button will default to Colors.grey[300].