dependencies:
 ...
 barcode_scan: ^1.0.0

<!--獲取相機權限-->
<uses-permission android:name="android.permission.CAMERA" />

<activity android:name="com.apptreesoftware.barcodescan.BarcodeScannerActivity"/>

buildscript {
  ext.kotlin_version = '1.2.31'
  ...
  dependencies {
    ...
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
  }
}
...

apply plugin: 'kotlin-android'
...
dependencies {
  implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
  ...
}

<key>NSCameraUsageDescription</key>
<string>Camera permission is required for barcode scanning.</string>

import 'package:barcode_scan/barcode_scan.dart';

// 掃描二維碼
Future scan() async {
 try {
  // 此處為掃碼結果，barcode為二維碼的內容
  String barcode = await BarcodeScanner.scan();
  print('掃碼結果: '+barcode);
 } on PlatformException catch (e) {
  if (e.code == BarcodeScanner.CameraAccessDenied) {
   // 未授予APP相機權限
   print('未授予APP相機權限');
  } else {
   // 掃碼錯誤
   print('掃碼錯誤: $e');
  }
 } on FormatException{
  // 進入掃碼頁面后未掃碼就返回
  print('進入掃碼頁面后未掃碼就返回');
 } catch (e) {
  // 掃碼錯誤
  print('掃碼錯誤: $e');
 }
}

flutter\.pub-cache\hosted\pub.flutter-io.cn\barcode_scan-1.0.0\android\src\main\kotlin\com\apptreesoftware\barcodescan\BarcodeScannerActivity.kt
flutter\.pub-cache\hosted\pub.flutter-io.cn\barcode_scan-1.0.0\android\src\main\kotlin\com\apptreesoftware\barcodescan\BarcodeScannerActivity.kt

flutter\.pub-cache\hosted\pub.flutter-io.cn\barcode_scan-1.0.0\ios\Classes\BarcodeScannerViewController.m