supvan_printer #

Flutter plugin for Supvan thermal printers (T50 / T50Plus / T50Pro).

Wraps the native Supvan Android SDK (supvan.jar) and iOS SDK (SFPrintSDK.xcframework) via Platform Channels, providing a unified Dart API for:

• Bluetooth device scanning
• Printer connection / disconnection
• Printer status query
• Printing text, barcodes (CODE_128), QR codes, and images

Getting Started #

Installation #

Add to your pubspec.yaml:

dependencies:
  supvan_printer:
    path: ../supvan_printer   # or publish to pub.dev / git

Android Setup #

1. Minimum SDK: The plugin requires minSdk 24 (Android 7.0+).

   In your app's android/app/build.gradle.kts:

   defaultConfig {
       minSdk = 24
   }
   

2. Permissions: The plugin declares all required Bluetooth permissions in its own AndroidManifest.xml. No additional manifest changes needed in your app.

3. Runtime permissions: You must request Bluetooth and location permissions at runtime before scanning. Consider using the permission_handler package.

iOS Setup #

1. Minimum deployment target: iOS 13.0+.

2. Info.plist: Add Bluetooth usage descriptions to your app's ios/Runner/Info.plist:

   <key>NSBluetoothAlwaysUsageDescription</key>
   <string>This app uses Bluetooth to connect to thermal printers.</string>
   <key>NSBluetoothPeripheralUsageDescription</key>
   <string>This app uses Bluetooth to connect to thermal printers.</string>
   

Usage #

Quick Start #

import 'package:supvan_printer/supvan_printer.dart';

final printer = SupvanPrinter.instance;

// 1. Listen for discovered devices
printer.scanResults.listen((device) {
  print('Found: ${device.name} (${device.id})');
});

// 2. Listen for connection state changes
printer.connectionState.listen((state) {
  print('Connection: $state');
});

// 3. Start scanning
await printer.startScan();

// 4. Connect to a device (after discovery)
await printer.connect(device.id);
// On Android, if the SDK rejects the device name, use:
// await printer.connect(device.id, bypassWhitelist: true);

// 5. Query printer status
final status = await printer.getStatus();
print(status); // PrinterStatus.ready, etc.

// 6. Print
await printer.print(PrintJob(
  labelWidth: 40,
  labelHeight: 30,
  copies: 1,
  density: 4,
  gap: 6,
  pages: [
    PrintPage(width: 40, height: 30, items: [
      PrintItem.text(
        x: 6, y: 5, width: 10, height: 2,
        content: 'Hello World',
        fontSize: 3,
      ),
      PrintItem.barcode(
        x: 1, y: 10, width: 23, height: 3,
        content: '123456',
      ),
      PrintItem.qrCode(
        x: 4, y: 15, width: 6, height: 6,
        content: 'https://example.com',
      ),
    ]),
  ],
));

// 7. Disconnect
await printer.disconnect();

Printing Images #

import 'dart:typed_data';

// Load image bytes (PNG format)
final Uint8List imageBytes = await loadImageBytes();

await printer.print(PrintJob(
  labelWidth: 40,
  labelHeight: 30,
  pages: [
    PrintPage(width: 40, height: 30, items: [
      PrintItem.image(
        x: 3, y: 3, width: 10, height: 10,
        imageBytes: imageBytes,
      ),
    ]),
  ],
));

API Reference #

SupvanPrinter #

PrinterStatus #

PrintItem Types #

PrintJob Parameters #

Platform Differences #

Troubleshooting #

Android: Device not connecting #

• Ensure Bluetooth and location permissions are granted at runtime.
• If the SDK rejects the device, try connect(id, bypassWhitelist: true).
• Stop scanning before connecting (stopScan() then connect()).

iOS: No devices found #

• Check that Bluetooth is enabled in Settings.
• Verify NSBluetoothAlwaysUsageDescription is in Info.plist.
• The SDK filters devices internally; ensure the printer is in pairing mode.

Both: Print fails silently #

• Query status first with getStatus() to check for material/cover issues.
• Ensure the label dimensions match the actual loaded material.