How to update a Screen UI from another Class in Flutter-CodePudding

So i have a Screen, HomeScreen. Now i have another class named LoginUtil which performs some operation. I am calling its method 'login' from Homescreen which works totally fine. But whatever response i get in LoginUtil ... i want to access it in HomeScreen but i am not sure as to how to do it.

HomeScreen

class HomeScreen extends StatefulWidget {
  @override
  State < HomeScreen > createState() => HomeScreenState();
}

class HomeScreenState extends State < HomeScreen > {
  var advertisingMessage = "Click here";
  static
  const advertisingUUID = "0000A002-0000-1000-8000-00805f9b34fb";
  static
  const bleChannel = MethodChannel('ble');
  final LoginUtil loginUtil = LoginUtil();
  var connection = 0;
  var connectionImage =
    "https://assets3.lottiefiles.com/packages/lf20_lbmtnnap.json";

  @override
  Widget build(BuildContext context) {
    performBleOperations();
    return Scaffold(
      drawer: NavigationDrawerWidget(),
      appBar: AppBar(
        title: Text("Home"),
        actions: [
          IconButton(
            icon: Icon(Icons.notifications),
            onPressed: () {},
          ),
          InkWell(
            onTap: () {
              Navigator.of(context)
                .push(MaterialPageRoute(builder: (context) => ScanScreen()));
            },
            child: Container(
              margin: EdgeInsets.only(right: 10),
              child: Image.asset("assets/scanner.png", height: 20, width: 20),
            ),
          )
        ],
      ),
      body: Column(
        children: [
          const SizedBox(height: 50.0),
            Text("Connected Devices: 0",
              textAlign: TextAlign.center, style: TextStyle(fontSize: 19)),
            Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                InkWell(
                  onTap: () {
                    showAdvertisingBottomSheet();
                  },
                  child: Stack(
                    alignment: Alignment.center,
                    children: [
                      Lottie.network(connectionImage,
                        height: 180.0, width: 180.0),
                      Text(advertisingMessage)
                    ],
                  ),
                ),
              ],
            ),
            Text("Waiting for a device to connect"),
            Container(
              width: double.infinity,
              color: const Color(0xFF09419B),
                child: Text("See Logs",
                  textAlign: TextAlign.center,
                  style: TextStyle(color: Colors.white)),
                margin: EdgeInsets.only(top: 20, left: 50, right: 50),
                padding: EdgeInsets.all(20),
            ),
            Container(
              width: double.infinity,
              color: const Color(0xFF09419B),
                child: Text("Create Downlink",
                  textAlign: TextAlign.center,
                  style: TextStyle(color: Colors.white)),
                margin: EdgeInsets.only(top: 20, left: 50, right: 50),
                padding: EdgeInsets.all(20),
            ),
            Container(
              width: double.infinity,
              color: const Color(0xFF09419B),
                child: Text("Track Trips",
                  textAlign: TextAlign.center,
                  style: TextStyle(color: Colors.white)),
                margin: EdgeInsets.only(top: 20, left: 50, right: 50),
                padding: EdgeInsets.all(20),
            ),
            Container(
              margin: EdgeInsets.only(
                top: 20,
              ),
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: [
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("12"), Text("Trucks")],
                          ),
                        ),
                      ),
                      Text("Out For Delivery"),
                    ],
                  ),
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("9"), Text("Trucks")],
                          ),
                        ),
                      ),
                      Text("Idle"),
                    ],
                  ),
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("122"), Text("")],
                          ),
                        ),
                      ),
                      Text("Alerts"),
                    ],
                  ),
                ]),
            ),
            Container(
              margin: EdgeInsets.only(
                top: 20,
              ),
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: [
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("1"), Text("Ongoing")],
                          ),
                        ),
                      ),
                      Text("Incoming Trip"),
                    ],
                  ),
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("12"), Text("Ongoing")],
                          ),
                        ),
                      ),
                      Text("Outgoing Trips"),
                    ],
                  ),
                  Column(
                    children: [
                      Card(
                        child: Container(
                          width: 70,
                          height: 70,
                          child: Column(
                            mainAxisAlignment: MainAxisAlignment.center,
                            children: [Text("12"), Text("Trucks")],
                          ),
                        ),
                      ),
                      Text("Out For Delivery"),
                    ],
                  ),
                ]),
            ),
        ],
      ),
    );
  }

  Future < void > performBleOperations() async {

    loginUtil.login("Jack", 18, callback: (String name, int age) {
      // showLoading = false;
      // userInfo = "name: $name, age: $age";
      setState(() {});
    });
  }

  void updateConnectionState() {
    print("Trying to update the connection state");
    var connectionState = loginUtil.connectionState;
    if (connectionState == 0) {
      setState(() {
        connectionImage =
          "https://assets3.lottiefiles.com/packages/lf20_cpjxufjf.json";
      });
    } else {
      setState(() {
        connectionImage =
          "https://assets3.lottiefiles.com/packages/lf20_lbmtnnap.json";
      });
    }
  }


}

LoginUtil

class LoginUtil {
  LoginUtil() {
    _channel.setMethodCallHandler(_methodCallHandler);
  }

  final MethodChannel _channel =
    const MethodChannel('my-channel');
  var connectionState;
  Function(String, int) ? _loginSuccessCallback;

  Future < void > login(String name, int age, {
    Function(String, int) ? callback
  }) async {
    _loginSuccessCallback = callback;
    var params = {
      'name': name,
      'age': age
    };
    // call native method 'login'
    try {
      await _channel.invokeMethod('login', params);
    } catch (e) {
      print(e.toString());
    }
  }

  Future < dynamic > _methodCallHandler(MethodCall call) async {
    print("Reached here my brother");
    String method = call.method;
    if (method == 'loginSuccess') {
      if (_loginSuccessCallback != null) {
        final map = call.arguments;
        connectionState = map['connectionState'];
        print("Connection state is: $connectionState");
      }
    }
  }

  getCurrentState() {
    print("Returning current state");
    return connectionState;
  }
}

Any help would be highly appreciated.

CodePudding user response：

This class will give you clear answer for your question, Here you can access your parent class from your child class

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'main1.dart';

void main() {
  runApp(MaterialApp(
    home: Modalbtn(),
  ));
}

class Modalbtn extends StatefulWidget {
  @override
  _ModalbtnState createState() => _ModalbtnState();
}

class _ModalbtnState extends State<Modalbtn> {
  String value = "0";
  // Pass this method to the child page.
  void _update(String newValue) {
    setState(() => value = newValue);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            IconButton(
              onPressed: () {
                showModalBottomSheet(
                    context: context,
                    builder: (BuildContext context) {
                      return Container(
                        height: 200,
                        child: Column(
                          children: [StatefulModalbtn(update: _update)],
                        ),
                      );
                    });
              },
              icon: Icon(Icons.add),
              iconSize: 20,
            ),
            Text(
              value,
              style: TextStyle(fontSize: 40),
            ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';

class StatefulModalbtn extends StatelessWidget {
  final ValueChanged<String> update;
  StatefulModalbtn({required this.update});

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: () => update("100"), // Passing value to the parent widget.

      child: Text('Update (in child)'),
    );
  }
}