How to add Kotlin support to your flutter project?

You simply have to add a single file in Kotlin format (example under android>main>java>your packagename>test.kt and it will automatically upgrade. Can be an empty file. Add it using android studio. answer reference: https://github.com/mintware-de/flutter_barcode_reader/issues/121

Doing it manually:

Check if you need to do this:

https://github.com/flutter/flutter/wiki/Upgrading-pre-1.12-Android-projects

Next create a new flutter project for reference and call it myapp.

Next, from myapp/android/build.gradle copy:

ext.kotlin_version = '1.3.50'

and

classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

Next, from myapp/android/app/build.gradle copy:

apply plugin: 'kotlin-android'

and

sourceSets {    main.java.srcDirs += 'src/main/kotlin'}

and

implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

Next, create the path according to you package path and copy the file myapp/android/app/src/main/kotlin/com/example/myapp/MainActivity.kt

Next, in the file MainActivity.kt replace 'package com.example.myapp' with your package.

Next, if MainActivity.java is an empty class then just delete it under ../android/app/src/main/java/..but if it is not then you will need change the class and its body to kotlin, copy it and only then delete it.