Barcode Scan2 Scanning

barcode_scan2 Barcode & QR Scanning Guide

barcode_scan2 is a Flutter camera plugin for scanning 2D barcodes and QR codes with sound null safety support, built-in flashlight control, and customizable scanning options.

Guidelines

• Native Permission Configuration (Mandatory):
  • iOS (Info.plist): Always add NSCameraUsageDescription with a user-facing explanation:

    <key>NSCameraUsageDescription</key>
    <string>Camera access is required to scan barcodes and QR codes.</string>
    

  • Android (AndroidManifest.xml): Ensure camera permission is declared:

    <uses-permission android:name="android.permission.CAMERA" />
    

• Initiating Scan:
  • Call final result = await BarcodeScanner.scan(options: ...);.
• Handling Scan Results:
  • Check result.type:
    • ResultType.Barcode: Successful scan. Access result.rawContent and result.format.
    • ResultType.Cancelled: User dismissed or backed out of the scanner. Do not treat as an error.
    • ResultType.Error: Access result.rawContent for error diagnostic information.
• Handling Permission Exceptions:
  • Wrap BarcodeScanner.scan() in a try-catch block catching PlatformException.
  • Check if (e.code == BarcodeScanner.cameraAccessDenied) to present a permissions dialog directing the user to system settings.
• Format Restrictions & Performance:
  • When scanning only QR codes, set restrictFormat: [BarcodeFormat.qr] in ScanOptions to speed up recognition.

Examples

1. Basic Barcode / QR Code Scanner

import 'package:barcode_scan2/barcode_scan2.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

Future<String?> scanCode(BuildContext context) async {
  try {
    final result = await BarcodeScanner.scan(
      options: const ScanOptions(
        strings: {
          'cancel': 'Cancel',
          'flash_on': 'Flash on',
          'flash_off': 'Flash off',
        },
        restrictFormat: [BarcodeFormat.qr],
        useCamera: -1, // Back camera default
        autoEnableFlash: false,
        android: AndroidOptions(
          aspectTolerance: 0.5,
          useAutoFocus: true,
        ),
      ),
    );

    switch (result.type) {
      case ResultType.Barcode:
        return result.rawContent;
      case ResultType.Cancelled:
        return null;
      case ResultType.Error:
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(content: Text('Scan error: ${result.rawContent}')),
        );
        return null;
    }
  } on PlatformException catch (e) {
    if (e.code == BarcodeScanner.cameraAccessDenied) {
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Camera permission was denied.')),
      );
    } else {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Unexpected error: ${e.message}')),
      );
    }
    return null;
  }
}

Common Pitfalls & Anti-Patterns

• ❌ Anti-pattern: Forgetting NSCameraUsageDescription in ios/Runner/Info.plist, causing immediate app crash on iOS when camera opens.
  • ✔️ Correct: Add the description string before calling BarcodeScanner.scan().
• ❌ Anti-pattern: Assuming result.rawContent is non-empty without checking result.type == ResultType.Barcode.
  • ✔️ Correct: Always verify result.type first.