Barcode HID Listener

A headless, zero-dependency Flutter package for intercepting, buffering, and validating physical HID barcode scanner keystrokes (USB/Bluetooth).

Designed for enterprise Retail POS, Warehouse Inventory, and Logistics applications, this package catches raw hardware keystrokes in the background and transforms them into clean, strongly-typed Dart streams—without requiring any native OS plugins.

✨ Features

• 🛡️ Two-Stage Symbology Gatekeeper: Built-in Regex validation for global retail and logistics formats (UPC, EAN, Code 39).
• ⏱️ Temporal Deduplication: Automatically ignores accidental double-scans within a configurable time window.
• 🔄 GS1 AI Normalization: Automatically intercepts and strips the 01 Application Identifier prefix from 16-digit hardware EAN-14 scans.
• 🚀 Dual Paradigm: Drop in a simple, declarative UI Widget, or run the headless Service inside your Riverpod/Bloc state controllers.
• 🚫 Zero Dependencies: Pure Dart. Runs flawlessly on iOS, Android, Windows, macOS, Linux, and Web.

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📦 Installation

Add it to your pubspec.yaml:

flutter pub add barcode_hid_listener

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💻 Usage

We provide two distinct ways to integrate barcode listening into your app depending on your architectural needs.

Option 1: The Declarative Widget Wrapper (Recommended for UI)

Wrap your screen or specific widget tree with BarcodeKeyboardListener. Focus management and route-visibility are handled automatically!

BarcodeKeyboardListener(
  // autoPauseOnFocus is true by default. The scanner will automatically 
  // pause if the user taps into a TextField!
  onBarcodeScanned: (capture) {
    print("Scanned: ${capture.rawValue}");
  },
  child: Scaffold(
    body: TextField(
      decoration: InputDecoration(labelText: 'Manual Entry (Scanner pauses while typing)'),
    ),
  ),
);

Option 2: The Imperative Service (For Advanced State Management)

If you are managing background streams inside a View Model, Bloc, or Riverpod Provider, you can instantiate the headless service directly.

import 'package:barcode_hid_listener/barcode_hid_listener.dart';

// 1. Initialize Configuration
final config = BarcodeScannerConfig(
  allowedFormats: BarcodeFormat.values,
  deduplicationWindow: const Duration(milliseconds: 500),
);

// 2. Instantiate Service
final service = BarcodeKeyboardService(config);

// 3. Listen to Streams
service.barcodeStream.listen((capture) {
  print('Success! GTIN: ${capture.rawValue}');
});

service.rejectionStream.listen((rejection) {
  print('Blocked: ${rejection.reason.name}');
});

// 4. Start Listening (Don't forget to call service.dispose() when done!)
service.start();

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⚙️ Configuration & Symbologies

BarcodeScannerConfig

You can tailor the hardware ingestion engine to your specific hardware environments using the BarcodeScannerConfig object:

Property	Default	Description
terminators	[LogicalKeyboardKey.enter]	Hardware keystrokes signaling the end of a scan.
bufferTimeout	100ms	Maximum elapsed time between keystrokes before the buffer resets. Filters out slow human typing.
deduplicationWindow	500ms	Time window where identical back-to-back scans are ignored.
allowedFormats	[] (All)	Whitelist of allowed symbologies. Unlisted formats are cleanly blocked.

Supported BarcodeFormat Values

The Two-Stage Gatekeeper currently detects and routes the following global standards:

• ean13 (Standard retail items)
• upcA (North American retail items)
• ean8 (Small retail items)
• upcE (Small North American retail items)
• ean14 / GTIN-14 (Outer cases and warehouse pallets)
• code39 (Alphanumeric inventory badges and asset tags)

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💡 Best Practices & Troubleshooting

Preventing TextField Focus Collisions (HID Wedge Behavior)

Because physical USB/Bluetooth HID scanners act as operating system keyboards, scanning a barcode while a TextField (like a search bar or manual input form) is focused can cause duplicate keystroke events between your active UI text field and the background hardware stream.

We provide 3 simple presentation-layer recipes (FocusNode Gatekeeping, Global Focus Shielding, and UI Deduplication) to handle this effortlessly in your app.

👉 Read the authoritative guide on avoiding HID Wedge Focus Collisions. The file is on the root of the project "GUIDE_HID_WEDGE_COLLISIONS.md".

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🐛 Bugs and 🤝 Contributing

We highly encourage you to report any malfunctions, bugs, or feature recommendations!

Please do not hesitate to leave an issue on our GitHub Issues page.

🤝 Acknowledgments

This package was inspired by the design philosophy of flutter_barcode_listener.

We built barcode_hid_listener as a modern, null-safe evolution because the original implementation relied on deprecated APIs (such as RawKeyboard.instance). Our version has been completely rewritten to utilize the modern HardwareKeyboard.instance event API, ensuring long-term compatibility with current and future Flutter versions, and adds enterprise-grade features like GS1 normalization, Two-Stage symbology gatekeeping, and proactive focus-shielding.