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

I'm learning Flutter, and I'm starting from the very basics. I'm not using MaterialApp. What's a good way to set the background color of the whole screen?

Here's what I have so far:

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 Center(child: new Text("Hello, World!"));
  }
}

Some of my questions are:

• What's a basic way to set the background color?
• What exactly am I looking at, on the screen? Which code "is" the background? Is there a thing to set the background color on? If not, what's a simple and appropriate "simple background" (in order to paint a background color).

Thanks for the help!

The code above generates a black screen with white text:

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)

      )
)

and it's another approach to change the color of background:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(home: Scaffold(backgroundColor: Colors.pink,),);
  }
}

I think you need to use MaterialApp widget and use theme and set primarySwatch with color that you want. look like below 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 new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

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!"));
    );
  }
}

I still cannot make this work. Any other ideas?

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'),
    );

On the basic example of Flutter you can set with backgroundColor: Colors.X of Scaffold

  @override
 Widget build(BuildContext context) {
   // This method is rerun every time setState is called, for instance as done
  // by the _incrementCounter method above.
   //
  // The Flutter framework has been optimized to make rerunning build methods
   // fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
  backgroundColor: Colors.blue,
  body: Center(
    // Center is a layout widget. It takes a single child and positions it
    // in the middle of the parent.
    child: Column(
      // Column is also layout widget. It takes a list of children and
      // arranges them vertically. By default, it sizes itself to fit its
      // children horizontally, and tries to be as tall as its parent.
      //
      // Invoke "debug painting" (press "p" in the console, choose the
      // "Toggle Debug Paint" action from the Flutter Inspector in Android
      // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
      // to see the wireframe for each widget.
      //
      // Column has various properties to control how it sizes itself and
      // how it positions its children. Here we use mainAxisAlignment to
      // center the children vertically; the main axis here is the vertical
      // axis because Columns are vertical (the cross axis would be
      // horizontal).
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        Text(
          'You have pushed the button this many times:',
        ),
        Text(
          '$_counter',
          style: Theme.of(context).textTheme.display1,
        ),
      ],
    ),
  ),
  floatingActionButton: FloatingActionButton(
    onPressed: _incrementCounter,
    tooltip: 'Increment',
    child: Icon(Icons.add_circle),
  ), // This trailing comma makes auto-formatting nicer for build methods.
);
}

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:

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 .