Setup Kotlin for Android Studio

Step 1: Setup the Kotlin Plugin in Android Studio

In order to ensure Android Studio support Kotlin, the first thing is to install the Kotlin Plugin for your Android Studio.

Android Studio → Preferences… →Plugins → Browse Repository → type “Kotlin” in search box → install

Plugins Browser, where you can find Kotlin Plugin for you to install.

That’s all the generically applied to your Android Studio. Only needed to do once per installation of Android Studio.

Step 2: Add Kotlin classpath to project Build.Gradle

For gradle to have Kotlin support, add the two classpaths below, i.e. Kotlin-Gradle-Plugin and Kotlin-Android-Extensions. Also in this file I setup the variable to define Kotlin version, that could be shared by all.

buildscript {
    ext.kotlin_version = "1.1.1"
    ext.supportLibVersion = "25.3.0"
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath "org.jetbrains.kotlin:kotlin-android-extensions:$kotlin_version"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

Step 3: Add Kotlin library and apply Kotlin Plugins in your module Build.gradle.

In the module that will use Kotlin, you will add the Kotlin library into it’s Build.gradle. Also remember to apply both the Kotlin Android and it’s extension plugin to your project (I often forgot this, after add the library).

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

android {
    // ... various gradle setup
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile "com.android.support:appcompat-v7:$supportLibVersion"
    compile "com.android.support:recyclerview-v7:$supportLibVersion"
    compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
}

Step 4: Ready to go…

Now you have setup Kotlin for your app development, you could start writing Kotlin code (in .kt extension). Another way is convert your Java file to Kotlin, using Shift-Alt-Cmd-K or Shift-Shift + search Convert Java File to Kotlin File.