lpapi_printer

lpapi_printer is a Flutter BLE label-printer client modeled after the DothanTech LPAPI Android SDK. It uses universal_ble for transport, implements LPAPI packet framing, discovers compatible BLE printers by SDK-style device names, and can rasterize Flutter drawing jobs into printer command bytes. This package writes in pure Dart, so it is portable to any platform supported by universal_ble, but it only implements the BLE transport at this time.

Features

• BLE scan/connect/disconnect through universal_ble.
• LPAPI-compatible packet framing and command helpers.
• Android SDK-style printer name detection, including -D... and -O... BLE printer names.
• Raster image printing with threshold, inversion, margins, copies, and page keys.
• Label-size scaling plus continuous/gap/hole/black-mark paper settings.
• Left, middle, and right media-position alignment for printers with centered or left-loaded paper.
• LPAPI-style drawing facade for text, QR codes, shapes, lines, and images.

Usage

final client =LpPrinterClient();
await client.requestPermissions();
await client.startScan();
final printers =await client.discoveredPrintersStream.first;
await client.connect(printers.first);
final api =LpApi(client: client);
api.startJob(48, 18, 0);
api.drawText('LPAPI BLE', 3, 2, 30, 5, 3.2, LpFontStyle.bold);
api.drawText('Flutter package', 3, 7, 30, 4, 2.4);
api.draw2DQRCode('https://pub.dev/packages/lpapi_printer', 34, 2, 12);
await api.commitJob(
options:constLpPrintOptions(
labelWidthMm:48,
labelHeightMm:18,
paperType:LpPaperType.gap,
darkness:LpPrintParamValue.defaultPrintDarkness,
speed:LpPrintParamValue.defaultPrintSpeed,
alignment:LpPrintAlignment.center,
),
);
await client.disconnect();

For custom labels, use LpApi:

final api =LpApi(client: client);
await api.openPrinterByAddress(printers.first);
api.startJob(48, 18, 0);
api.drawText('Gateway', 2, 2, 44, 6, 4);
api.draw2DQRCode('payload', 2, 8, 8);
await api.commitJob();

For pre-rendered label images, use LpPrinterClient.printPng or LpPrinterClient.printImage directly.

LpPrintParamValue.maxPrintDarkness follows the documented LPAPI value 14. When the connected printer reports a larger darknessCount, the client maps that documented max value to the printer's real maximum. Use client.printerInfo?.maxPrintDarkness for custom settings sliders.

Permissions

lpapi_printer uses universal_ble for BLE scanning and connections, so your app must configure the platform Bluetooth permissions required by universal_ble before calling scan or connect APIs. Runtime permission requests can be made through this package:

final client =LpPrinterClient();
await client.requestPermissions(
withAndroidFineLocation:false,
);
final granted =await client.hasPermissions();

See the universal_ble permission guide: https://pub.dev/packages/universal_ble#permissions

Notes

This package intentionally implements BLE printers only. Classic SPP, USB, WiFi, NFC, and the Android WebView JavaScript bridge are outside the supported surface.