How do I set the background color of my main screen in Flutter?

Question

You can set background color to All Scaffolds in application at once.

just set scaffoldBackgroundColor: in ThemeData

 MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(scaffoldBackgroundColor: const Color(0xFFEFEFEF)),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );

I think you can also use a scaffold to do the white background. Here's some piece of code that may help.

import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
  @override
    Widget build(BuildContext context) {

      return new MaterialApp(
        title: 'Testing',
        home: new Scaffold(
        //Here you can set what ever background color you need.
          backgroundColor: Colors.white,
        ),
      );
    }
}

Hope this helps 😊.

Here's one way that I found to do it. I don't know if there are better ways, or what the trade-offs are.

Container "tries to be as big as possible", according to https://flutter.io/layout/. Also, Container can take a decoration, which can be a BoxDecoration, which can have a color (which, is the background color).

Here's a sample that does indeed fill the screen with red, and puts "Hello, World!" into the center:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new Container(
      decoration: new BoxDecoration(color: Colors.red),
      child: new Center(
        child: new Text("Hello, World!"),
      ),
    );
  }
}

Note, the Container is returned by the MyApp build(). The Container has a decoration and a child, which is the centered text.

See it in action here:

There are many ways of doing it, I am listing few here.

1. Using backgroundColor

   Scaffold(
     backgroundColor: Colors.black,
     body: Center(...),
   )
   

2. Using Container in SizedBox.expand

   Scaffold(
     body: SizedBox.expand(
       child: Container(
         color: Colors.black,
         child: Center(...)
       ),
     ),
   )
   

3. Using Theme

   Theme(
     data: Theme.of(context).copyWith(scaffoldBackgroundColor: Colors.black),
     child: Scaffold(
       body: Center(...),
     ),
   )
   

Scaffold(
      backgroundColor: Constants.defaulBackground,
      body: new Container(
      child: Center(yourtext)

      )
)

you should return Scaffold widget and add your widget inside Scaffold

suck as this code :

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return Scaffold(
          backgroundColor: Colors.white,
          body: Center(child: new Text("Hello, World!"));
    );
  }
}