Flutter, Number Counter app

We created simple flutter app. This app only for increasing and decreasing the number.

Main and MaterialApp

MaterialApp class creates an instance of WidgetsApp.

void main() {
  runApp(
    new Center(
      child: new MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "Number Count",
      theme: new ThemeData(
          primarySwatch: Colors.blueGrey
      ),
      home: new NumberCountDemo(),
    );
  }
}
class NumberCountDemo extends StatefulWidget {
  @override
  _NumberCountDemoState createState() => new _NumberCountDemoState();
}

Variable initialization

int _n = 0;

Declare and initialize a variable. Using underscore, variable will be a Private member.

Add function

void add() {
  setState(() {
    _n++;
  });
}

Add function is used to increase the number size.

Minus function

void minus() {
  setState(() {
    if (_n != 0) 
      _n--;
  });
}

Similarly, Minus function is used to decrease the number size. If condition is true, the value of n will be decreased.

Scaffold

Creates a visual scaffold for material design widgets.

@override
Widget build(BuildContext context) {
  return new Scaffold(
    appBar: new AppBar(title: new Text("Number Count")
    ),
    body: new Container(
      child: new Center(
        child: new Row(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          children: <Widget>[
            new FloatingActionButton(
              onPressed: add,
              child: new Icon(Icons.add, color: Colors.black,),
              backgroundColor: Colors.white,),

            new Text('$_n',
                style: new TextStyle(fontSize: 60.0)),

            new FloatingActionButton(
              onPressed: minus,
              child: new Icon(
               const IconData(0xe15b, fontFamily: 'MaterialIcons'),
                 color: Colors.black),
              backgroundColor: Colors.white,),
          ],
        ),
      ),
    ),
  );
}

App Screenshots