check call back

callback.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
  Color _w = Colors.white;
  VoidCallback? callback;
  Function(int)? callback2;
  Function(List<dynamic>)? callback3;
  CallBackLogic _callBackLogic = CallBackLogic();

  _buttonTap() {
    callback3(e) {
      setState(() {
        _w = Colors.cyan;
        List<dynamic> d = e as List<dynamic>;
        _counter = int.parse(d.first);
        _counter += double.parse(d.last).round();
        _showMyDialog();
      });
    }

    callback2(e) {
      setState(() {
        Navigator.of(context).pop();
        _w = Colors.yellow;
        _counter = e;
        _callBackLogic.clallBackLogic3(callback3);
      });
    }

    callback() {
      setState(() {
        _counter = 1;
        _showMyDialog();
        _w = Colors.red;
        _callBackLogic.clallBackLogic2(callback2);
      });
    }

    _callBackLogic.clallBackLogic(callback);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        backgroundColor: _w,
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
            TextButton.icon(
              onPressed: () => _buttonTap(),
              icon: Icon(Icons.tab),
              label: Text('Call Back Check'),
            ),
          ],
        ),
      ),
    );
  }

  Future<void> _showMyDialog() async {
    return showDialog<void>(
      context: context,
      barrierDismissible: false, // user must tap button!
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text(_counter.toString()),
          content: SingleChildScrollView(
            child: ListBody(
              children: const <Widget>[
                Text('This is a demo alert dialog.'),
                Text('Would you like to approve of this message?'),
              ],
            ),
          ),
          actions: <Widget>[
            TextButton(
              child: const Text('Approve'),
              onPressed: () {
                Navigator.of(context).pop();
                _buttonTap();
              },
            ),
          ],
        );
      },
    );
  }
}

class CallBackLogic {
  clallBackLogic(VoidCallback? callback) {
    Future.delayed(Duration(milliseconds: 1000)).then((_) => callback?.call());
  }

  clallBackLogic2(Function(int)? callback) {
    Future.delayed(Duration(milliseconds: 1000)).then((_) => callback?.call(2));
  }

  clallBackLogic3(Function(List<dynamic>)? callback) {
    Future.delayed(Duration(milliseconds: 1000))
        .then((_) => callback?.call(["1", "1.9"]));
  }
}

2022-05-19.23.17.47.mov