main and runApp

Learn how main connects MaterialApp via runApp.

main and runApp

The entry point of every Flutter app is the main function. Inside main you call runApp, which attaches the root widget to the screen. The root widget is usually MaterialApp or CupertinoApp; they provide theme, navigation and Material/Cupertino components.

import 'package:flutter/material.dart';

void main() {
  runApp(
    MaterialApp(
      home: Text('Merhaba'),
    ),
  );
}

Role of MaterialApp

MaterialApp gives the app a Material Design theme, title bar, navigation infrastructure and base theme settings. The home parameter sets the app's opening screen. Without MaterialApp, widgets like Text lack default styles.

MaterialApp(
  title: 'İlk Uygulama',
  home: Scaffold(
    appBar: AppBar(title: Text('Başlık')),
    body: Center(child: Text('Merhaba')),
  ),
)

Exercise Start with MaterialApp

Inside main, first write a print('basladi') call, then call runApp with a MaterialApp whose home is Text('Selam').

Show example solution

import 'package:flutter/material.dart';

void main() {
  print('basladi');
  runApp(MaterialApp(home: Text('Selam')));
}

Test yourself

Which widget is usually given to runApp as the root?
- ListView
- Column
- Scaffold
- MaterialApp
Show answer

MaterialApp — The root widget is usually MaterialApp; Scaffold and Column sit beneath it.

Bind the root widget

runApp(
  ____(
    home: Text('Selam'),
  ),
);

Show answer

runApp(
  MaterialApp(
    home: Text('Selam'),
  ),
);

main, runApp, MaterialApp

main

App entry point
runApp

Attaches the root widget to the screen
MaterialApp

Provides Material theme and navigation
home

Sets the opening screen

Next lesson: Hot reload

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