qrcode_barcode_scanner 4.0.0

Plugins to manage the reading of QR code or barcode from an external device as a keyboard.

QRCode & Barcode Scanner

Overview

The QRCode & Barcode Scanner plugin manages QR and Barcode scanning from external "keyboard wedge" devices, offering a streamlined API for integration in Android applications.

Important: This package currently supports Android only.

Features

• Simple Integration: Use the QrcodeBarcodeScanner class to easily handle scan events.
• Layout independent: Scanned values are decoded from the physical keys the scanner emits, so they are not corrupted by the keyboard layout configured on the device.
• Customizable Callbacks: Register custom callback functions to handle scanned data in real-time.
• Android Only: This plugin is developed with Android compatibility in mind.
• Tested Devices: Supports external scanning devices such as Sunmi Blink.

Installation

Add the following dependency in your pubspec.yaml file:

flutter pub add qrcode_barcode_scanner

Usage Example

import 'package:qrcode_barcode_scanner/qrcode_barcode_scanner.dart';

class MyScannerApp extends StatefulWidget {
  const MyScannerApp({super.key});

  @override
  State<MyScannerApp> createState() => _MyScannerAppState();
}

class _MyScannerAppState extends State<MyScannerApp> {
  String? _scanValue;
  late final QrcodeBarcodeScanner _scanner;

  @override
  void initState() {
    super.initState();
    _scanner = QrcodeBarcodeScanner(
      onScannedCallback: (String value) {
        setState(() => _scanValue = value);
      },
    );
  }

  @override
  void dispose() {
    _scanner.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("QR & Barcode Scanner")),
      body: Center(child: Text(_scanValue ?? "Waiting for scan...")),
    );
  }
}

Keyboard layouts

A keyboard wedge scanner does not send text: it sends key codes, exactly like a physical keyboard. Virtually all of them are shipped configured for a US layout, while the device translates those key codes with the layout the user has selected. The two disagree on every key whose position differs, so the value silently changes:

Scanner sends	Read on an Italian layout	Read on a German layout
=	ì	´
+	]	*
/	-	-
_	?	?

This breaks base64 payloads in particular, where +, / and the = padding are part of the alphabet — a QR code ending in In0= is read as In0ì.

Since 4.0.0 the plugin decodes the physical key of each event through a US QWERTY table, so the scanned value is the same whatever layout the device uses. If your scanner is instead programmed with the same layout as the device, opt out:

QrcodeBarcodeScanner(
  keyMapping: ScannerKeyMapping.platformCharacter,
  onScannedCallback: (String value) { /* ... */ },
);

API Documentation

Class: QrcodeBarcodeScanner

Constructor:

QrcodeBarcodeScanner({
  required ScannedCallback onScannedCallback,
  ScannerKeyMapping keyMapping = ScannerKeyMapping.usPhysicalLayout,
  Duration scanDelay = const Duration(milliseconds: 100),
  bool submitOnTerminator = true,
  bool ignoreWhenTextInputFocused = true,
});

Parameters:

Parameter	Default	Description
onScannedCallback	—	Called with the scanned value once the scan is complete.
keyMapping	usPhysicalLayout	How key events are turned into characters. See Keyboard layouts.
scanDelay	100 ms	Idle time after the last key event before the scan is delivered.
submitOnTerminator	true	Deliver the scan as soon as the scanner sends its Enter/Tab suffix, without waiting for scanDelay.
ignoreWhenTextInputFocused	true	Ignore key events while a text field owns the focus, so the scanner does not steal its input.

Methods:

• flush(): delivers the scan in progress immediately.
• cancelScan(): discards the scan in progress.
• dispose(): releases the keyboard listener. Always call it when the scanner is no longer needed.

Tested Devices

This plugin has been tested with the following devices:

• Sunmi Blink

Requirements

• Dart ^3.8.0, Flutter >=3.32.0
• Android minSdk 24, compileSdk 36

Additional Resources

For more detailed documentation and advanced use cases, check out the Wiki.

Changelog

Check out the Changelog for details on recent updates.

Contributing

Want to contribute? Check out the Contribution Guide to get started!

License

This project is licensed under the MIT License. See the LICENSE file for details.