Accessing a method of state class using its stateful widget?

Question

I have a method in state class, but I need to access that method in outside using its widget class reference,

class TestFormState extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _testState();
  }
}

class _testFormState extends State<TestFormState> {
  int count = 1;

  @override
  Widget build(BuildContext context) {
    return Center(
        child: Container(
        color: Colors.green,
            child: Text("Count : $count"),
        ),
    );
  }

  clickIncrease(){
    setState(() { count += 1; });
  }
}

and I need to access the above widget`s clickIncrease in another widget, like below code,

class TutorialHome extends StatelessWidget {

    TestFormState test;

  @override
  Widget build(BuildContext context) {
    // Scaffold is a layout for the major Material Components.
    return Scaffold(
      body: Column(
         children: <Widget>[
            test = TestFormState(),
            FlatButton(
               child: Text("Increase"),
               onPressed: (){
                  test.state.clickIncrease(); // This kind of thing I need to do
               },
            ),
         ]
      ),
    );
  }

I wrote above code just for demostrate the issue.

Answer 1

I have a trick, but I don't know if it is a bad practice or not.

class TestFormState extends StatefulWidget {

  _TestFormState _testFormState;

  @override
  State<StatefulWidget> createState() {
    _testFormState = _TestFormState();
    return _testFormState;
  }
}

class _TestFormState extends State<TestFormState> {
  int count = 1;

  @override
  Widget build(BuildContext context) {
    return Center(
      child: Container(
        color: Colors.green,
        child: Text("Count : $count"),
      ),
    );
  }

  clickIncrease(){
    setState(() { count += 1; });
  }
}

Now, you can access it here :

class TutorialHome extends StatelessWidget {

  TestFormState test;

  @override
  Widget build(BuildContext context) {
    // Scaffold is a layout for the major Material Components.
    return Scaffold(
      body: Column(
          children: <Widget>[
            TextButton(
              child: Text("Increase"),
              onPressed: () {
                test._testFormState
                    .clickIncrease(); // This is accessable
              },
            ),
          ]
      ),
    );
  }
}

I suggest taking a look at ValueNotifier