Importing Statements

import 'package:expense_tracker/database_helper.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'transaction_screen.dart';
import 'profile_screen.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:sms_advanced/sms_advanced.dart';

MyApp class

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Expense Tracker',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
        useMaterial3: true,
      ),
      home: const HomeScreen(),
    );
  }
}

class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key});

  @override
  State<HomeScreen> createState() => _HomeScreenState();
}

HomeScreenState class

class _HomeScreenState extends State<HomeScreen> {
  static const platform =
      MethodChannel('com.example.expense_tracker/notifications');

  String _transactionMessage = 'No transactions yet.';
  int _selectedIndex = 0;
  List<Map<String, dynamic>> transactions = [];

  @override
  void initState() {
    super.initState();
    _startNotificationListener();
    requestSmsPermission();
    readSmsMessages();
    fetchAndDisplayTransactions();
  }

  void readSmsMessages() async {
    debugPrint("readSmsMessages called");
    final SmsQuery query = SmsQuery();

    // final List<SmsMessage> messages = await query.getAllSms;

    List<SmsQueryKind> kinds = [SmsQueryKind.Inbox, SmsQueryKind.Sent];
    final List<SmsMessage> messages = await query.querySms(kinds: kinds);

    debugPrint("messages length: ${messages.length}");
    if (messages.isNotEmpty) {
      debugPrint("if");
      for (var message in messages) {
        if (isUpiTransaction(message.body.toString())) {
          // Extract relevant data (amount, transaction ID, etc.)
          setState(() {
            _transactionMessage = message.body.toString();
            storeTransaction(extractTransactionData(_transactionMessage));
            debugPrint(_transactionMessage);
          });
        }
      }
    }
  }

  Map<String, dynamic> extractTransactionData(String messageBody) {
    // Use regex or pattern matching to extract data from message
    RegExp amountPattern = RegExp(r'(\d+(\.\d{1,2})?)');
    RegExp transactionIdPattern = RegExp(r'Transaction ID: (\w+)');

    String? amount = amountPattern.firstMatch(messageBody)?.group(0);
    String? transactionId =
        transactionIdPattern.firstMatch(messageBody)?.group(1);

    return {
      'amount': amount,
      'transactionId': transactionId,
      'message': messageBody,
    };
  }

  bool isUpiTransaction(String messageBody) {
    // Simple keyword check for UPI-related SMS
    return messageBody.contains('credited') || messageBody.contains('debited');
  }

  Future<void> _startNotificationListener() async {
    try {
      await platform.invokeMethod('startNotificationListener');
    } on PlatformException catch (e) {
      debugPrint("e.message: ${e.message}");
    }

    platform.setMethodCallHandler((call) async {
      if (call.method == 'notifyTransaction') {
        String transactionData = call.arguments;
        setState(() {
          _transactionMessage = transactionData;
          debugPrint(_transactionMessage);
        });
      }
    });
  }

  Future<void> requestSmsPermission() async {
    var status = await Permission.sms.status;
    if (!status.isGranted) {
      await Permission.sms.request();
    }
  }

  void _onItemTapped(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }

  void storeTransaction(Map<String, dynamic> transactionData) async {
    await DatabaseHelper.instance.insertTransaction(transactionData);
  }

  Future<List<Map<String, dynamic>>> fetchAndDisplayTransactions() async {
    List<Map<String, dynamic>> dbtransactions =
        await DatabaseHelper.instance.getTransactions();
    transactions = dbtransactions;
    return dbtransactions;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Expense Tracker'),
      ),
      body: IndexedStack(
        index: _selectedIndex,
        children: [
          TransactionScreen(
            transactions: transactions,
          ),
          const ProfileScreen(),
        ],
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.list),
            label: 'Transactions',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            label: 'Profile',
          ),
        ],
        currentIndex: _selectedIndex,
        selectedItemColor: Colors.blue,
        onTap: _onItemTapped,
      ),
    );
  }
}

I want to read all the sms of user's device that's why I am using "sms_advanced" package in Flutter, but when I am using "querySms()" function to get the list of all the messages which are already in his device then I am getting this following error

"Unhandled Exception: MissingPluginException(No implementation found for method getSent o n channel plugins.elyudde.com/querySMS)"

I think it is not able to find the function which I am calling to get the list of all messages, i.e, querySms()

I have also added a debugPrint Statement in "readSmsMessages()" function

When I am running my app using "flutter run" command then it is showing the debug message "readSmsMessages called" in console but after that it is also showing the above error "MissingPluginException"

that's why I am not able to move furthur, so can anyone help me in this please.

You are probably getting that exception because that package or that function of the package is not (yet) implemented on the platform you are using. Flutter packages or certain parts of a package may not be available on all platforms.

In this case, sms_advanced is only available on Android, iOS and in the browser. This is show on the website of the package here. This package also does not implement all of its functionality across each platforms yet as show here:

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