flutter_print_label 0.1.1

Bluetooth label printer plugin (TSPL) for Android and iOS. Supports budget Chinese label printers (VOZY, Xprinter, Gprinter, ...) that advertise BLE without a name.

flutter_print_label

Bluetooth label printer plugin (TSPL) for Android and iOS.

[Sample 100x150mm label printed with flutter_print_label] [Thermal label printer printing a shipping label]

Built for real-world budget label printers — VOZY, Xprinter, Gprinter and similar Chinese thermal printers used for shipping labels — including the quirks that usually make them hard to use from Flutter:

• Finds printers that advertise BLE without a name. Many cheap printers do this; most plugins silently skip them. This plugin reports them with a generated name like Unknown (1A2B) so they can be listed and selected.
• Works with non-standard write services. After connecting (iOS), every service/characteristic is discovered and the first writable characteristic is picked, preferring well-known printer services (49535343-..., FF00, FFE0, 18F0, ...). No vendor SDK required — pure CoreBluetooth.
• Chunked writes. Data is written in MTU-sized chunks with a short delay, so large payloads (bitmap labels) don't overflow the printer's BLE buffer.
• Stable connect/disconnect cycles. One central manager for the app's lifetime; disconnecting really drops the link so the printer starts advertising again and can be re-discovered without power-cycling it.
• Android dual transport. Bluetooth Classic (SPP) for paired printers and a real BLE scan for unpaired ones.
• connected is only reported when the printer is actually ready to receive data (iOS: a writable characteristic has been found).

Getting started

iOS

Add to ios/Runner/Info.plist:

<key>NSBluetoothAlwaysUsageDescription</key>
<string>Need Bluetooth access to connect to label printers</string>
<key>UIBackgroundModes</key>
<array>
    <string>bluetooth-central</string>
</array>

Do not pair the printer in Settings > Bluetooth on iOS — just scan and connect from the app.

Android

All required permissions are declared by the plugin and requested at runtime automatically (BLUETOOTH_SCAN / BLUETOOTH_CONNECT on Android 12+, location permission on older versions). When Bluetooth is off, the system "enable Bluetooth" dialog is shown automatically on scan.

Usage

import 'dart:io';
import 'package:flutter_print_label/flutter_print_label.dart';

final printer = FlutterPrintLabel.instance;

// 1. Scan.
// iOS always scans BLE. On Android, isBle: false returns the paired-devices
// list; isBle: true performs a real BLE scan (finds unpaired printers too).
printer.scan(isBle: Platform.isIOS).listen((device) {
  print('found: ${device.name} (${device.address})');
});

// 2. Connect, then wait for `connected`.
await printer.connect(device);
printer.connectionStatus.listen((status) {
  if (status == PrinterConnectionStatus.connected) {
    print('ready to print');
  }
});

// 3. Print a TSPL label (100 x 150 mm shipping label).
await printer.printTspl(
  'SIZE 100 mm,150 mm\r\n'
  'GAP 3 mm,0 mm\r\n'
  'DIRECTION 1\r\n'
  'CLS\r\n'
  'TEXT 50,80,"3",0,2,2,"HELLO"\r\n'
  'BARCODE 50,320,"128",100,1,0,2,2,"123456789"\r\n'
  'PRINT 1,1\r\n',
);

// Raw bytes work too (e.g. TSPL BITMAP payloads):
await printer.sendBytes(bytes);

// Disconnect when done.
await printer.disconnect();

See example/lib/main.dart for a complete shipping-label layout (barcode, dividers, specs, footer and QR code) that prints exactly the label shown in the screenshot above.

Handling unnamed printers

Devices without a name are emitted as Unknown (xxxx) / Printer (xxxx). A common UX is to hide them behind a "show unnamed devices" toggle, but always show the device the user previously selected (match by address).

iOS extras

// After a hot restart the native connection may still be alive while your
// Dart state is gone (and a connected printer stops advertising, so scanning
// won't find it). Restore it:
final connected = await printer.getConnectedDevice();

// React to the Bluetooth radio being switched off, and help the user turn it
// back on (shows the system alert whose Settings button opens the Bluetooth
// settings page):
printer.bluetoothOnStream.listen((on) { /* update UI */ });
await printer.showEnableBluetoothAlert();

TSPL quick reference

Command	Meaning
SIZE 100 mm,150 mm	Label size
GAP 3 mm,0 mm	Gap between labels
CLS	Clear the image buffer
TEXT x,y,"font",rotation,x-mul,y-mul,"content"	Draw text
BARCODE x,y,"128",height,readable,rotation,narrow,wide,"content"	Draw barcode
QRCODE x,y,ECC,cellWidth,mode,rotation,"content"	Draw QR code
BAR x,y,width,height	Draw a filled bar (divider line)
BITMAP x,y,widthBytes,height,mode,data	Draw bitmap (for images/PDF rasters)
PRINT 1,1	Print

Credits

Based on flutter_pos_printer_platform (MIT, © 2022 Gustavo Morales). The iOS side has been rewritten from scratch in pure CoreBluetooth; the Android side keeps its battle-tested SPP/GATT implementation with fixes for unnamed BLE devices.