Advanced

State

A state is the data present in a graphical object at a certain moment

State

A state is the data present in a graphical object at a certain moment

In this case, we need an ephemeral, aka local, state. This kind of state represents just a single Widget's data.

State: example

class MyWidget extends StatefulWidget {
  //...
  State<MyWidget> createState() => _MyWidget();
}

State: example

class _MyWidget extends State<MyWidget>{
  int myState;
  void initState() {
    super.initState();
    myState = 0;
  }
  void myMethod() {
    setState(() { myState = 1; })
  }
}

Controllers

In flutter, controllers allow to give control to the parent widget over its child's state.

Controllers

In flutter, controllers allow to give control to the parent widget over its child's state.

If the state is our data, the controller is what manages it.

Controllers: how to use them

• Add a listener to it
• Attach it to a TextField
• Enjoy your data

Controllers: example

class _MyCustomFormState extends State<MyCustomForm> {
  final myController = TextEditingController(text: "some default text");
  @override
  void initState() {
    super.initState();
    myController.addListener(_printLatestValue);
  } 
}

Controllers: example

TextField(
  controller: myController,
),

Controllers: example

void _printLatestValue() {
  final text = myController.text;
  print('Second text field: $text (${text.characters.length})');
}