(MethodCall) => Null' is not a subtype of type '((MethodCall) => Future<dynamic>)?'

[excode]

he following _CastError was thrown building Builder: type '(MethodCall) => Null' is not a subtype of type '((MethodCall) => Future)?' in type cast

The relevant error-causing widget was MaterialApp-[#3d82a]

When the exception was thrown, this was the stack

0 new BlueThermalPrinter._

package:blue_thermal_printer/blue_thermal_printer.dart:39

1 BlueThermalPrinter._instance

package:blue_thermal_printer/blue_thermal_printer.dart:42

STUCK IN THIS issue please help.

Thank you

[kakzaki]

thanks for the information, i fixed it at ver 1.1.3

[excode]

Hello still getting the same error

version updated in pubspec flutter clean then debug

Still same error

type '(MethodCall) => Null' is not a subtype of type '((MethodCall) => Future)?' in type cast

The relevant error-causing widget was MaterialApp-[#889c1]

type '(MethodCall) => Null' is not a subtype of type '((MethodCall) => Future)?' in type cast

The relevant error-causing widget was MaterialApp-[#889c1] lib/…/jounalHome/JournalHome.dart:96 When the exception was thrown, this was the stack

0 new BlueThermalPrinter._

package:blue_thermal_printer/blue_thermal_printer.dart:37

1 BlueThermalPrinter._instance

package:blue_thermal_printer/blue_thermal_printer.dart:40

2 BlueThermalPrinter._instance (package:blue_thermal_printer/blue_thermal_printer.dart)

package:blue_thermal_printer/blue_thermal_printer.dart:1

3 BlueThermalPrinter.instance

package:blue_thermal_printer/blue_thermal_printer.dart:42

4 new _MedicineDetailsState

package:mypaaa/…/medicine/medicine_details.dart:45 ...

[excode]

[kakzaki]

can you run the example code?

[excode]

import 'package:flutter/material.dart'; import 'package:flutter_bloc/flutter_bloc.dart'; import 'package:mypaaa/blocs/appointment/appointment.dart'; import 'package:mypaaa/blocs/authentication/user_repository.dart'; import 'package:mypaaa/blocs/medicine/bloc.dart'; import 'package:mypaaa/blocs/journal/journal.dart'; import 'package:mypaaa/serviceLocator.dart'; import 'package:mypaaa/utils/allTranslation.dart'; import 'package:mypaaa/widgets/form-inputs/Loading.dart'; import 'package:mypaaa/widgets/ui_elements/PrescriptionData.dart'; import 'package:flutter/services.dart'; import 'package:blue_thermal_printer/blue_thermal_printer.dart'; import 'dart:io'; import 'package:mypaaa/utils/country_codes.dart' as countryList; import 'package:mypaaa/utils/printing.dart';

class MedicineDetails extends StatefulWidget { final Journal journal; final Appointment appointment; MedicineDetails({ required this.journal, required this.appointment, }); @override State createState() => _MedicineDetailsState(); }

class _MedicineDetailsState extends State { BlueThermalPrinter bluetooth = BlueThermalPrinter.instance;

List _devices = []; late BluetoothDevice _device; bool _connected = false; bool _pressed = false; bool _showDropDown = false; String pathImage = ''; String username = ""; String usernameMasked = ""; String currencyCode = ""; Printing printing = Printing(); MedicineBloc _medicineBloc = locator.get(); @override void initState() { super.initState();

initPlatformState();

initSavetoPath();

}

initSavetoPath() async {

Map<String, String> user = await UserRepository().getRegistrationPhone();

setState(() {
  //pathImage = '$dir/$filename';
  username = user["phone"] ?? '';
  usernameMasked = username.replaceRange(2, 10, ".");

  Map<String, dynamic> _countryMapMap =
      countryList.getCountryCodes(widget.journal.currency, "curSymbol");
  if (_countryMapMap["curCode"] != null) {
    currencyCode = _countryMapMap["curCode"] ?? "USD";
  } else {
    currencyCode = "USD";
  }
});

}

void load() { _medicineBloc.add(SearchMedicineEvent( pageno: 0, searchWord: "", isReport: 1, journalId: widget.journal.id, appointmentId: widget.appointment.id)); }

@override Widget build(BuildContext contextFrm) { //print("###sdsdsdsdsds####"); return Scaffold( resizeToAvoidBottomInset: true, appBar: AppBar( title: Text(widget.appointment.name + " " + widget.appointment.age.toString() + "/" + widget.appointment.genderChar), ), body: Container( width: MediaQuery.of(context).size.width, child: BlocBuilder( bloc: _medicineBloc, builder: (context, state) { if (state is MedicineLoading) { if (state.journalId != widget.journal.id || state.appointmentId != widget.appointment.id || state.isReport == 0) { load(); } return Loading(); } else if (state is MedicineInitial) { load();

              return Text("");
            } else if (state is MedicineLoaded) {
              if (state.journalId != widget.journal.id ||
                  state.appointmentId != widget.appointment.id ||
                  state.isReport == 0) {
                load();
                return Text("");
              } else {
                return SingleChildScrollView(
                  child: Column(
                    children: [
                      Row(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        mainAxisAlignment: MainAxisAlignment.spaceAround,
                        children: [
                          // if (_showDropDown)
                          DropdownButton(
                            items: _getDeviceItems(),
                            onChanged: (BluetoothDevice? value) =>
                                setState(() {
                              if (value != null) {
                                _device = value;

                                _showDropDown = true;
                              }
                            }),
                            value: _device,
                          ),
                          RaisedButton(
                            onPressed: _pressed
                                ? null
                                : _connected
                                    ? _disconnect
                                    : _connect,
                            child:
                                Text(_connected ? 'Disconnect' : 'Connect'),
                          ),
                          RaisedButton(
                            onPressed: _connected
                                ? () {
                                    initPlatformState();
                                    printing.printBluetoothPrescription(
                                        bluetooth,
                                        currencyCode,
                                        usernameMasked,
                                        widget.journal,
                                        state.medicine,
                                        widget.appointment);
                                  }
                                : null,
                            child: Text(allTranslations.text("print")),
                          ),
                        ],
                      ),
                      PrescriptionData(
                          journal: widget.journal,
                          data: state.medicine,
                          appointment: widget.appointment,
                          printMode: true),
                    ],
                  ),
                );
              }
            } else {
              return Text("");
            }
          }),
    ));

}

Future initPlatformState() async { List devices = [];

try {
  devices = await bluetooth.getBondedDevices();
} on PlatformException {
  // TODO - Error
}

bluetooth.onStateChanged().listen((state) {
  switch (state) {
    case BlueThermalPrinter.CONNECTED:
      setState(() {
        _connected = true;
        _pressed = false;
      });
      break;
    case BlueThermalPrinter.DISCONNECTED:
      setState(() {
        _connected = false;
        _pressed = false;
      });
      break;
    default:
      print(state);
      break;
  }
});

if (!mounted) return;
setState(() {
  _devices = devices;
});

}

List<DropdownMenuItem> _getDeviceItems() { List<DropdownMenuItem> items = []; if (_devices.isEmpty) { items.add(DropdownMenuItem( child: Text('NONE'), )); } else { _devices.forEach((device) { items.add(DropdownMenuItem( child: Text(device.name ?? ''), value: device, )); }); } return items; }

void _connect() { if (_device == null) { show('No device selected.'); } else { bluetooth.isConnected.then((isConnected) { if (isConnected == false) { bluetooth.connect(_device).catchError((error) { setState(() => _pressed = false); }); setState(() => _pressed = true); } }); } }

void _disconnect() { bluetooth.disconnect(); setState(() => _pressed = true); }

//write to app path Future writeToFile(ByteData data, String path) { final buffer = data.buffer; return new File(path).writeAsBytes( buffer.asUint8List(data.offsetInBytes, data.lengthInBytes)); }

Future show( String message, { Duration duration: const Duration(seconds: 3), }) async { await new Future.delayed(new Duration(milliseconds: 100)); Scaffold.of(context).showSnackBar( new SnackBar( content: new Text( message, style: new TextStyle( color: Colors.white, ), ), duration: duration, ), ); }

@override void dispose() { bluetooth.disconnect(); //bluetooth = null; super.dispose(); } }

==========================

printing.dart

import 'dart:convert';

import 'package:intl/intl.dart'; import 'package:blue_thermal_printer/blue_thermal_printer.dart'; import 'package:mypaaa/blocs/appointment/appointment.dart'; import 'package:mypaaa/blocs/invoice/invoice.dart'; import 'package:mypaaa/blocs/invoiceproduct/invoiceproduct.dart'; import 'package:mypaaa/blocs/journal/journal.dart'; import 'package:mypaaa/blocs/medicine/medicine.dart'; import 'package:mypaaa/blocs/productblog/address.dart'; import 'package:mypaaa/blocs/productblog/jconfig.dart'; import 'package:mypaaa/utils/allTranslation.dart'; import 'package:mypaaa/utils/config.dart'; import 'package:mypaaa/utils/helper.dart';

class Printing { void printBluetooth( BlueThermalPrinter bluetooth, String currencyCode, String usernameMasked, Journal journal, List listData, Invoice invoice, [String qrCode = '', String paidAmount = '', String returnAmount = '']) async { JConfig jConfig = JConfig.fromMap(json.decode(journal.config)); Address address = Address.fromMap(json.decode(journal.address)); InvoiceProduct item; String lft, rgt; double subTotal, itemTotal; String line = "--------------------------------"; //String itemLine = ". . . . . . . . ."; itemTotal = 0; bluetooth.isConnected.then((isConnected) { if (isConnected == true) { bluetooth.printCustom(journal.title, 1, 1); bluetooth.printCustom(address.address, 0, 1); bluetooth.printCustom( address.city + " " + address.state + " " + address.country, 0, 1); bluetooth.printCustom(journal.enterBy, 0, 1);

    bluetooth.printNewLine();
    bluetooth.printCustom(invoice.businessName, 0, 0);
    bluetooth.printCustom(invoice.contactNumber, 0, 0);
    if (invoice.invoiceType == 1) {
      if (invoice.invoiceInfos.dtype == OrderModes.home) {
        if (invoice.territory.length > 0) {
          bluetooth.printCustom(invoice.invoiceInfos.hourseRoadNo, 0, 0);
          //bluetooth.printCustom(invoice.territory, 0, 0);
        }
        if (invoice.destinationAddress.length > 0) {
          // bluetooth.printCustom(invoice.territory, 0, 0);
          bluetooth.printCustom(
              invoice.invoiceInfos.address +
                  " " +
                  invoice.invoiceInfos.city +
                  " " +
                  invoice.invoiceInfos.country +
                  " " +
                  invoice.invoiceInfos.postcode,
              0,
              0);
        }
        if (invoice.latitude > 0 && invoice.longitude > 0) {
          String locationCode = invoice.latitude.toString() +
              "#MyPaaaLoc#" +
              invoice.longitude.toString();
          bluetooth.printQRcode(locationCode, 250, 250, 1);
        }
      }
    }

    bluetooth.printLeftRight(invoice.invoiceId, invoice.date, 0);
    bluetooth.printCustom(line, 1, 1);
    // bluetooth.printNewLine();
    int counter = 0;
    for (int i = 0; i < listData.length; i++) {
      counter = i + 1;
      item = listData[i];
      lft = item.quantity.toString() +
          " " +
          item.unitName +
          " x " +
          item.unitPrice.toString();
      subTotal = item.quantity * item.unitPrice;
      itemTotal += subTotal;
      rgt = subTotal.toStringAsFixed(2);
      bluetooth.printCustom(
          counter.toString() + ") " + item.productName, 0, 0);
      //bluetooth.printCustom("Unit:" + item.unitName, 1, 0);
      bluetooth.printLeftRight(lft, rgt, 0);
      //bluetooth.printLeftRight(itemLine, "", 0);
    }
    bluetooth.printCustom(line, 1, 1);
    bluetooth.printLeftRight("Sub", itemTotal.toString(), 1);
    if (invoice.gst > 0) {
      bluetooth.printCustom(jConfig.tax_label, 1, 0);
      bluetooth.printLeftRight(
          jConfig.tax + " % ", invoice.gst.toStringAsFixed(2), 0);
    }
    if (invoice.discount > 0) {
      bluetooth.printCustom(jConfig.discount_label, 1, 0);
      bluetooth.printLeftRight(
          jConfig.discount + " % ", invoice.discount.toStringAsFixed(2), 0);
    }
    if (invoice.others > 0) {
      bluetooth.printCustom(jConfig.other_label, 1, 0);
      bluetooth.printLeftRight(
          jConfig.other + " % ", invoice.others.toStringAsFixed(2), 0);
    }
    bluetooth.printCustom(line, 1, 1);
    bluetooth.printLeftRight(
        "Total", invoice.finalPrice.toStringAsFixed(2), 1);
    if (paidAmount.length > 0) {
      bluetooth.printLeftRight("Payment", paidAmount, 1);
      bluetooth.printLeftRight("Change", returnAmount, 1);
    }
    bluetooth.printNewLine();
    bluetooth.printCustom(
        Helper().formatCurrency(invoice.finalPrice, currencyCode + " "),
        1,
        1);
    bluetooth.printNewLine();
    bluetooth.printCustom("Thank you!", 2, 1);
    if (qrCode.length > 10) {
      bluetooth.printQRcode(qrCode, 250, 250, 1);
    }
    DateFormat printTimeFormat =
        DateFormat('dd/MM/yyyy').add_jm(); // DateFormat.yMd().add_jm();
    String printTime =
        printTimeFormat.format(DateTime.now()).toString().trim();
    bluetooth.printLeftRight(printTime, usernameMasked.trim(), 0);
    //bluetooth.printCustom(line, 1, 1);
    bluetooth.printCustom("MyPaaa a product from ExCode.Net", 0, 1);
    //bluetooth.printLeftRight(DateTime.now().toIso8601String(), '', 1);
    bluetooth.printNewLine();
    //bluetooth.printNewLine();
    bluetooth.paperCut();
  }
});

}

void printBluetoothPrescription( BlueThermalPrinter bluetooth, String currencyCode, String usernameMasked, Journal journal, List listData, Appointment appointment, [String qrCode = '']) async { JConfig jConfig = JConfig.fromMap(json.decode(journal.config)); Address address = Address.fromMap(json.decode(journal.address)); Medicine item; List plist = MedProcedures.list; String lft, rgt; String subTotal, itemTotal; String line = "--------------------------------"; String line2 = ". . . . . . . . . . . . . . . . "; String unitName2, unitName, name, procedure; int qty = 0; Helper helper = Helper(); String days = allTranslations.text("days"); //String itemLine = ". . . . . . . . ."; itemTotal = ""; subTotal = ""; bluetooth.isConnected.then((isConnected) { if (isConnected == true) { bluetooth.printCustom(journal.title, 1, 1); bluetooth.printCustom( journal.subCategoryId + " " + jConfig.speciality, 1, 1); bluetooth.printCustom(address.address, 0, 1); bluetooth.printCustom( address.city + " " + address.state + " " + address.country, 0, 1); bluetooth.printCustom(journal.enterBy, 0, 1);

    bluetooth.printNewLine();
    bluetooth.printCustom(appointment.name, 0, 0);
    bluetooth.printCustom(appointment.contactNumber, 0, 0);

    bluetooth.printLeftRight(
        appointment.genderChar, appointment.age.toString() + " yrs", 0);
    bluetooth.printCustom(line, 1, 1);
    // bluetooth.printNewLine();
    int counter = 0;
    for (int i = 0; i < listData.length; i++) {
      counter = i + 1;
      item = listData[i];
      name = item.name;
      unitName2 = "";
      unitName = "";
      itemTotal = "";
      subTotal = "";
      if (item.procedureType == MedProcedures.medicationIdx) {
        procedure = item.drugType;
        unitName2 =
            helper.medicineIntake(item.intake, item.times, item.unit);
        qty = helper.daysCount(
            item.intake, item.times, item.continueForDays, 1);
        if (qty > 0) {
          unitName = qty.toString() + " " + days;

          // name = item.name;
        }
        if (item.continueForDays > 0) {
          subTotal = " (" +
              item.continueForDays.toString() +
              " " +
              item.unit +
              ")";
        }
      } else {
        procedure = plist[item.procedureType];
      }

      lft = unitName2;
      //subTotal = item.quantity * item.unitPrice;
      //itemTotal += subTotal;
      rgt = unitName;

      bluetooth.printCustom(
          counter.toString() + ") " + procedure + " - " + name, 0, 0);
      if (item.procedureType == MedProcedures.medicationIdx) {
        bluetooth.printCustom(subTotal + " " + unitName, 0, 0);
        //bluetooth.printCustom("Unit:" + item.unitName, 1, 0);
        bluetooth.printCustom(lft, 0, 0);
        bluetooth.printCustom(item.beforeAfterMealText, 0, 0);
        //bluetooth.printLeftRight(itemLine, "", 0);
        if (item.continueCondition.length > 0) {
          bluetooth.printCustom(item.continueCondition, 0, 0);
        }
      }
      bluetooth.printCustom(line2, 1, 1);
    }
    bluetooth.printCustom(line, 1, 1);
    // bluetooth.printLeftRight("Sub", itemTotal.toString(), 1);

    //bluetooth.printNewLine();

    bluetooth.printNewLine();
    bluetooth.printCustom("Thank you!", 2, 1);
    if (qrCode.length > 10) {
      bluetooth.printQRcode(qrCode, 250, 250, 1);
    }
    DateFormat printTimeFormat =
        DateFormat('dd/MM/yyyy').add_jm(); // DateFormat.yMd().add_jm();
    String printTime =
        printTimeFormat.format(DateTime.now()).toString().trim();
    bluetooth.printLeftRight(printTime, usernameMasked.trim(), 0);
    //bluetooth.printCustom(line, 1, 1);
    bluetooth.printCustom("MyPaaa a product from ExCode.Net", 0, 1);
    //bluetooth.printLeftRight(DateTime.now().toIso8601String(), '', 1);
    bluetooth.printNewLine();
    //bluetooth.printNewLine();
    bluetooth.paperCut();
  }
});

} }

========

THERE IS NO ERROR in my code but while try to load the page it throws the error

[excode]

Any update Mr @kakzaki kakzaki

Thank you

[danieramiz]

I have the same error

[unger1984]

To fix it, replace default constructor in 34 line of blue_thermal_printer.dart from this:

  BlueThermalPrinter._() {
    _channel.setMethodCallHandler((MethodCall call) {
      _methodStreamController.add(call);
    } as Future<dynamic> Function(MethodCall)?);
  }

to this:

BlueThermalPrinter._() {
    _channel.setMethodCallHandler((MethodCall call) async{
      _methodStreamController.add(call);
    });
  }

[vishnuagbly]

@kakzaki your example app is not migrated to null safety that is why it is working fine their, use dart migrate to migrate your example app to null safety

[mehdikazmii]

have you found the solution? if yes can you please help me?

[BLUECALF]

same error type '(MethodCall) => Null' is not a subtype of type '(MethodCall) => Future' in type cast using bluetooth_print: PACKAGE.

please help if anyone knows .

[BLUECALF]

This package works with my bluetooth earphone, it was updated 3days ago. you can view this package if you need bluetooth printing. havent tested with printer. but it connects & thats progress. https://pub.dev/packages/blue_print_pos