blue_thermal_printer

https://pub.dev/packages/blue_thermal_printer

A new Flutter plugin for connecting to thermal printer via bluetooth (Android Only), this plugin is still under development Note: Migrate your project to AndroidX

Getting Started

1. Depend on it

Add this to your package's pubspec.yaml file:

dependencies:
  blue_thermal_printer: ^any

2. Install it

You can install packages from the command line:

with Flutter:

$ flutter packages get

Alternatively, your editor might support flutter packages get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

 import 'package:blue_thermal_printer/blue_thermal_printer.dart';

EXAMPLE:

import 'dart:io';
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:blue_thermal_printer/blue_thermal_printer.dart';
import 'package:flutter/services.dart';
import 'package:path_provider/path_provider.dart';

void main() => runApp(new MyApp());

class MyApp extends StatefulWidget {
 @override
 _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {

  BlueThermalPrinter bluetooth = BlueThermalPrinter.instance;

  List<BluetoothDevice> _devices = [];
  BluetoothDevice _device;
  bool _connected = false;
  bool _pressed = false;
  String pathImage;

  @override
  void initState() {
   super.initState();
   initPlatformState();
   initSavetoPath();
  }

 initSavetoPath()async{
    //read and write
    //image max 300px X 300px
    final filename = 'yourlogo.png';
    var bytes = await rootBundle.load("assets/images/yourlogo.png");
    String dir = (await getApplicationDocumentsDirectory()).path;
    writeToFile(bytes,'$dir/$filename');
    setState(() {
     pathImage='$dir/$filename';
   });
 }


  Future<void> initPlatformState() async {
    List<BluetoothDevice> 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;
   });
  }

 @override
 Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Blue Thermal Printer'),
       ),
        body: Container(
         child: ListView(
           children: <Widget>[
             Padding(
               padding: const EdgeInsets.fromLTRB(10.0, 10.0, 10.0, 0.0),
               child: Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                 children: <Widget>[
                   Text(
                      'Device:',
                     style: TextStyle(
                        fontWeight: FontWeight.bold,
                     ),
                    ),
                   DropdownButton(
                      items: _getDeviceItems(),
                      onChanged: (value) => setState(() => _device = value),
                      value: _device,
                   ),
                   RaisedButton(
                      onPressed:
                     _pressed ? null : _connected ? _disconnect : _connect,
                      child: Text(_connected ? 'Disconnect' : 'Connect'),
                    ),
                 ],
               ),
             ),
              Padding(
                padding: const EdgeInsets.only(left: 10.0, right: 10.0, top: 50),
                child:  RaisedButton(
                  onPressed: _connected ? _tesPrint : null,
                 child: Text('TesPrint'),
               ),
             ),
            ],
         ),
        ),
     ),
   );
 }


  List<DropdownMenuItem<BluetoothDevice>> _getDeviceItems() {
    List<DropdownMenuItem<BluetoothDevice>> 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) {
          bluetooth.connect(_device).catchError((error) {
           setState(() => _pressed = false);
         });
         setState(() => _pressed = true);
       }
      });
    }
 }


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

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

  void _tesPrint() async {
    //SIZE
    // 0- normal size text
    // 1- only bold text
    // 2- bold with medium text
    // 3- bold with large text
    //ALIGN
    // 0- ESC_ALIGN_LEFT
    // 1- ESC_ALIGN_CENTER
    // 2- ESC_ALIGN_RIGHT
    bluetooth.isConnected.then((isConnected) {
    if (isConnected) {
        bluetooth.printNewLine();
        bluetooth.printCustom("HEADER",3,1);
        bluetooth.printNewLine();
        bluetooth.printImage(pathImage);   //path of your image/logo
        bluetooth.printNewLine();
        //bluetooth.printImageBytes(bytes.buffer.asUint8List(bytes.offsetInBytes, bytes.lengthInBytes));
        bluetooth.printLeftRight("LEFT", "RIGHT",0);
        bluetooth.printLeftRight("LEFT", "RIGHT",1);
        bluetooth.printLeftRight("LEFT", "RIGHT",1,format: "%-15s %15s %n");
        bluetooth.printNewLine();
        bluetooth.printLeftRight("LEFT", "RIGHT",2);
        bluetooth.printLeftRight("LEFT", "RIGHT",3);
        bluetooth.printLeftRight("LEFT", "RIGHT",4);
        bluetooth.printNewLine();
        bluetooth.print3Column("Col1", "Col2", "Col3",1);
        bluetooth.print3Column("Col1", "Col2", "Col3",1,format: "%-10s %10s %10s %n");
        bluetooth.printNewLine();
        bluetooth.print4Column("Col1","Col2","Col3","Col4",1);
        bluetooth.print4Column("Col1","Col2","Col3","Col4",1,format: "%-8s %7s %7s %7s %n" );
        bluetooth.printNewLine();
        String testString = " čĆžŽšŠ-H-ščđ";
        bluetooth.printCustom(testString, 1, 1, charset: "windows-1250");
        bluetooth.printLeftRight("Številka:", "18000001", 1, charset: "windows-1250");
        bluetooth.printCustom("Body left",1,0);
        bluetooth.printCustom("Body right",0,2);
        bluetooth.printNewLine();
        bluetooth.printCustom("Thank You",2,1);
        bluetooth.printNewLine();
        bluetooth.printQRcode("Insert Your Own Text to Generate", 200, 200, 1);
        bluetooth.printNewLine();
        bluetooth.printNewLine();
        bluetooth.paperCut();
        }
   });
  }


 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,
      ),
    );
 }
}

Note: make sure to upgrade your project to compileSdkVersion 31

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