更改颤动中TextFormField的默认边框颜色

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        // 设置主题颜色
        primaryColor: Colors.blue,
        accentColor: Colors.red,
        // 设置TextFormField的边框颜色
        inputDecorationTheme: InputDecorationTheme(
          // 更改颤动中TextFormField的默认边框颜色
          focusedBorder: OutlineInputBorder(
            borderSide: BorderSide(color: Colors.green),
          ),
        ),
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter App'),
      ),
      body: Center(
        child: TextFormField(
          decoration: InputDecoration(
            labelText: 'Username',
          ),
        ),
      ),
    );
  }
}