Unresolved reference: BR (Android Studio)

Question

My top level build.gradle:

buildscript {
    ext.kotlin_version = '1.2.41'
    ext.lifecycle_version = "1.1.1"
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

My project level build.gradle:

android {
    ...
    dataBinding {
        enabled = true
    }
}

dependencies {
    ...
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation "android.arch.lifecycle:extensions:$lifecycle_version"
}

I also added android.databinding.enableV2=true to gradle.properties per Google documents (https://developer.android.com/topic/libraries/data-binding/start)

When I try to run, it shows Unresolved reference: BR error in my BaseViewHolder class. It seems that BR class has been properly generated but it also says duplicate class found in the file .../R.java when I mouse over the class name. What have I done wrong?

fun bind(obj: Any) {
        binding.setVariable(BR.obj, obj)
        binding.executePendingBindings()
}

Answer 1

For Android Studio 3.3, Gradle 3.3.0 and Databinding v2, the only line that needs to be added to fix this issue is in your (app's or modules) build.gradle:

apply plugin: "kotlin-kapt"