pos_flutter_printer

A Flutter plugin to print structured receipts (with text, images, QR codes, font styles, alignment, and margins) on Bluetooth POS printers.

🚀 Features

• Print styled text with custom font, size, and alignment
• Print base64 images with align and width options
• Print QR codes with alignment and size
• Margin control (top and bottom)
• Supports Android Bluetooth POS printers
• Fully customizable via Flutter JSON-based structure

⚠️ Note: Make sure only one Bluetooth printer is paired with your POS terminal. The plugin automatically connects to the first paired device.

📦 Installation

Add this plugin in your pubspec.yaml:

dependencies:
  pos_flutter_printer: ^1.0.0

🛠 Usage

1. Import the plugin

import 'package:pos_flutter_printer/pos_flutter_printer.dart';

2. Use it in your code

3. Bill Receipt Example

String formatRow(String item, int qty, double rate) {
  final total = (qty * rate).toStringAsFixed(2);
  return "${item.padRight(14).substring(0, 14)}"
      "${qty.toString().padLeft(4)}"
      "${rate.toStringAsFixed(2).padLeft(6)}"
      "${total.padLeft(8)}";
}

String generateDivider(String char, {int lineLength = 32}) {
  return List.filled(lineLength, char).join();
}

String leftRightAlign(String left, String right, {int totalWidth = 32}) {
  const spacer = ' ';
  int spaceCount = totalWidth - left.length - right.length;
  if (spaceCount < 1) {
    final allowedLeft = totalWidth - right.length - 1;
    left = left.substring(0, allowedLeft.clamp(0, left.length));
    spaceCount = 1;
  }
  return '$left${spacer * spaceCount}$right';
}

final lines = [
  {
    "text": "4Brains Technologies",
    "align": "center",
    "size": 1,
    "bold": true,
    "font": "RobotoMono-Regular.ttf",
  },
  {
    "text": "T0067, Vashi, MH",
    "align": "center",
    "size": 1,
    "font": "RobotoMono-Regular.ttf",
  },
  {
    "text": generateDivider('-'),
    "align": "left",
    "font": "RobotoMono-Regular.ttf",
    "size": 1,
  },
  {
    "text": "Item".padRight(14) +
             "Qty".padLeft(4) +
             "Rate".padLeft(6) +
             "Total".padLeft(8),
    "align": "left",
    "size": 1,
    "bold": true,
    "font": "RobotoMono-Regular.ttf",
  },
  {
    "text": formatRow("Pen", 2, 10.0),
    "align": "left",
    "size": 1,
    "font": "RobotoMono-Regular.ttf",
  },
  {
    "text": formatRow("Notebook", 1, 50.0),
    "align": "left",
    "size": 1,
    "font": "RobotoMono-Regular.ttf",
  },
  {
    "text": generateDivider('-'),
    "align": "left",
    "font": "RobotoMono-Regular.ttf",
    "size": 1,
  },
  {
    "text": leftRightAlign("Total", "₹ 100"),
    "bold": false,
    "size": 2,
    "marginTop": 10,
    "align": "left",
    "font": "RobotoMono-Regular.ttf",
  },
];

final result = await PosFlutterPrinter.print(
  lines: lines,
  topMargin: 40,
  bottomMargin: 60,
);

final lines = [
  {
    "text": "THANK YOU",
    "align": "center",
    "size": 4,
    "font": "Roboto-Regular.ttf",
    "bold": true
  },
  {
    "text": "Pawan Kumar",
    "align": "center",
    "bold": false,
    "size": 3,
    "font": "Roboto-Regular.ttf",
  },
  {
    "image": "BASE64_IMAGE_STRING",
    "width": 250,
    "align": "center"
  },
  {
    "qr": "https://4brains.in",
    "width": 200,
    "align": "center"
  }
];

final result = await PosFlutterPrinter.print(
  lines: lines,
  topMargin: 30,
  bottomMargin: 60,
);

print("Result: \$result");

Fonts

Place your font file (e.g. Roboto-Regular.ttf) in:

android/src/main/assets/fonts/

Manifest Permissions

In your plugin's AndroidManifest.xml:

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />

🧩 Parameters for Each Line

Key	Type	Description
text	String	Text to print
size	int	Font size scale (1 to 4)
bold	bool	Bold text
align	String	"left", "center", or "right"
font	String	Font filename in assets/fonts
image	String	Base64 image data
qr	String	Text/URL for QR code
width	int	Image or QR size in pixels
marginTop	int	Optional top margin before this line

📋 License

MIT License. Created by 4Brains Technologies.