createState and State

Learn how createState produces the State object.

createState

The createState method of a StatefulWidget produces a State object when the widget is placed on screen. This State holds the widget's changing data for its entire lifetime. Flutter calls createState once each time the widget is inserted into the tree; the same State lives until the widget is removed.

class Sayac extends StatefulWidget {
  const Sayac({super.key});

  @override
  State<Sayac> createState() => _SayacState();
}

class _SayacState extends State<Sayac> {
  int deger = 0;

  @override
  Widget build(BuildContext context) {
    return Text('$deger');
  }
}

State and setState

The State class holds the widget's variable data and build method. To change data you call setState; it marks the State as dirty and makes Flutter call build again. If you update a variable without setState, the screen does not refresh.

class _SayacState extends State<Sayac> {
  int deger = 0;

  void artir() {
    setState(() {
      deger = deger + 1;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Text('$deger');
  }
}

Exercise Print createState info

In main, print two lines with print: createState uretir and state yasar.

Show example solution

void main() {
  print('createState uretir');
  print('state yasar');
}

Test yourself

When is createState called?
- Once when the widget is first inserted into the tree
- Every time the widget rebuilds
- Every time setState is called
- When the app closes
Show answer

Once when the widget is first inserted into the tree — createState is called once when the widget is first inserted into the tree and produces the State object; it does not repeat on every build.

createState method

@override
State&lt;Sayac&gt; ____() =&gt; _SayacState();

Show answer

@override
State&lt;Sayac&gt; createState() =&gt; _SayacState();

createState and State

createState

Method that produces the State object
State nesnesi

Holds variable data
setState

Marks State as dirty
_SayacState

Implementer of the State class

Next lesson: The setState method

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies