Call a function from another stateful class in the build method of a class

December 22, 2022

I have two stateful classes and I want to trigger the function triggerFunction() from one class in second class’s build method with onPressed event of a button. Here are the both classes:

import 'package:flutter/material.dart';

class TriggerClass extends StatefulWidget {
  const TriggerClass({Key? key}) : super(key: key);

  @override
  State<TriggerClass> createState() => _TriggerClassState();
}

class _TriggerClassState extends State<TriggerClass> {

  void triggerFunction(){}

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(),
    );
  }
}

The Second class:

import 'package:flutter/material.dart';

class UIClass extends StatefulWidget {
  const UIClass({Key? key}) : super(key: key);

  @override
  State<UIClass> createState() => _UIClassState();
}

class _UIClassState extends State<UIClass> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ElevatedButton(
          onPressed: () {
             // Here I want to call triggerFunction()
          },
          child: const Text('Trigger Function'),
        ),
      ),
    );
  }
}

If I use simple class without state, it does call the function but when using stateful, it doesn’t.

>Solution :

Try below code hope its help to you remove _ from TriggerClassState()

Your Trigger Class included with Function

class TriggerClass extends StatefulWidget {
  const TriggerClass({Key? key}) : super(key: key);

  @override
  State<TriggerClass> createState() => TriggerClassState();
}

class TriggerClassState extends State<TriggerClass> {
  void triggerFunction() {
    print('Button Pressed');
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(),
    );
  }
}

Your UIClass Widget call your triggerFunction

class UIClass extends StatefulWidget {
  const UIClass({Key? key}) : super(key: key);

  @override
  State<UIClass> createState() => _UIClassState();
}

class _UIClassState extends State<UIClass> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            // Here I want to call triggerFunction()
            TriggerClassState().triggerFunction();
          },
          child: const Text('Trigger Function'),
        ),
      ),
    );
  }
}