import 'package:flutter/material.dart';

class Home extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            SizedBox(
              width: 200,
              child: TextButton(
                onPressed: () { },
                child: Text('center'),
              ),
            ),
            SizedBox(height: 16),
            SizedBox(
              width: 200,
              child: ElevatedButton(
                onPressed: () { },
                child: Text('centerRight'),
              ),
            ),
            SizedBox(height: 16),
            SizedBox(
              width: 200,
              child: OutlinedButton(
                onPressed: () { },
                child: Text('centerLeft'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}

void main() {
  runApp(
    MaterialApp(
      home: Home(),
      theme: ThemeData.light().copyWith(
        textButtonTheme: TextButtonThemeData(
          style: TextButton.styleFrom(alignment: Alignment.center),
        ),
        elevatedButtonTheme: ElevatedButtonThemeData(
          style: ElevatedButton.styleFrom(alignment: Alignment.centerRight),
        ),
        outlinedButtonTheme: OutlinedButtonThemeData(
          style: OutlinedButton.styleFrom(alignment: Alignment.centerLeft),
        ),
      ),
    ),
  );
}