add barcode scan

android/app/build.gradle

@@ -92,6 +92,8 @@ flutter {
     source '../..'
 }
 
+apply plugin: 'kotlin-android'
+
 dependencies {
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
@@ -100,6 +102,7 @@ dependencies {
     implementation 'com.google.firebase:firebase-analytics:17.5.0'
     implementation 'com.google.firebase:firebase-auth:19.0.0'
     implementation 'com.google.firebase:firebase-messaging:20.1.0'
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 }
 
 apply plugin: 'com.google.gms.google-services'

android/app/src/main/AndroidManifest.xml

@@ -4,6 +4,7 @@
     <uses-permission android:name="android.permission.INTERNET"/>
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
+    <uses-permission android:name="android.permission.CAMERA" />
 
     <!-- io.flutter.app.FlutterApplication is an android.app.Application that
          calls FlutterMain.startInitialization(this); in its onCreate method.