The setState method

Learn that setState triggers a rebuild.

The setState method

setState is the method that signals Flutter to call build again after you update data inside the State. The code you write inside setState changes the data; after setState returns, Flutter marks the State as dirty and runs build again in the next frame.

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

dirty and rebuild

When setState is called, the State is marked as dirty. In the next frame, Flutter calls build again on every dirty State. This process is known as rebuild. Changes made without setState do not trigger build, so they never reach the screen.

// wrong: no setState, screen does not refresh
void artirYanlis() {
  deger = deger + 1;
}

// right: setState triggers build
void artirDogru() {
  setState(() {
    deger = deger + 1;
  });
}

Exercise Print setState info

In main, print two lines with print: setState tetikler and dirty bekler.

Show example solution

void main() {
  print('setState tetikler');
  print('dirty bekler');
}

Test yourself

What does setState do?
- Completely restarts the app
- Removes the widget from the tree
- Marks the data change and triggers build
- Creates a new State object
Show answer

Marks the data change and triggers build — setState marks the data change and signals Flutter to call build again.

setState call

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

Show answer

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

setState concepts

setState çağrısı

Triggers build again
rebuild

build method called again
dirty

State waiting to be redrawn
next frame

Moment build runs

Next lesson: initState and dispose

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