Getting Started with Kotlin on Android with IntelliJ IDEA EAP 16
I recently spoke with some people in Tokyo who are using Kotlin in a production Android app. Kotlin is less cumbersome to write than Java and is therefore easier to maintain. By using Kotlin, Lambda functions can also be used on Android. Exciting.
Android work is fascinating in theory. Working with Java is neither fun nor exciting. I really like the idea of using something less cumbersome like Kotlin for Android projects.
Kotlin is a modern language with some functional features. It was written to interoperate seamlessly with Java code. Kotlin can also be compiled to JavaScript source code. The home page describes it as a “statically typed programming language for the JVM, Android and the browser”.
Kotlin was primarily developed by JetBrains, the makers of IntelliJ IDEA. Android studio is essentially a customized version of IntelliJ. A lot of thought went into making sure Kotlin works well on Android.
Idiomatic Kotlin with lambda functions does increase total method count. Multidex and ProGuard can be used to get around the dex file limit of 65,536 methods. Having said that, it is generally the libraries that push Android apps over the dex limit.
The Kotlin website has a good guide on getting started with Kotlin on Android. Writing this post is largely an excuse for me to give it a shot with IntelliJ EAP instead of Android Studio.
Software Versions
$ date -u "+%Y-%m-%d %H:%M:%S +0000" 2016-02-21 10:46:17 +0000 $ uname -vm Darwin Kernel Version 15.3.0: Thu Dec 10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64 x86_64 $ java -version java version "1.8.0_25" Java(TM) SE Runtime Environment (build 1.8.0_25-b17) Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode) $ cat /Applications/IntelliJ\ IDEA\ 16\ EAP.app/Contents/Info.plist | grep -A 1 CFBundleGetInfoString | grep -v CFBundleGetInfoString | sed 's/^\ *]*>//g' IntelliJ IDEA EAP IU-144.4199.23, build IU-144.4199.23. Copyright JetBrains s.r.o., (c) 2000-2016 $ cat $ANDROID_SDK/tools/source.properties | grep Pkg.Revision Pkg.Revision=24.4.1 $ cat $ANDROID_SDK/platform-tools/source.properties | grep Pkg.Revision Pkg.Revision=23.1 $ ls $ANDROID_SDK/build-tools/ 23.0.2Instructions
The first thing I did was download the latest version of IntelliJ IDEA EAP. I’m not afraid of using software that is not necessarily “stable”. The next thing I did, was use the android command to update Android SDK components.
After the setup, I worked through the guide on the Kotlin site. Their guide covers Android Studio. Below, I document what I did with IntelliJ IDEA.
Android SDK had to be configured in the new version of IntelliJ. Go to Configure | Project Defaults | Project Structure | SDKs and enter the Android SDK home path and Build target. Apply. OK. Go to Configure | Project Defaults | Project Structure | Project | Project SDK and make sure Android SDK is selected.
Start a new project. I did not have a project open, so I clicked Create New Project. If a project is open, File | New | Project… can be used.
Select Android and fill in the Application Name and Company Domain. The default Target Android Devices will work. Next. Select a Blank Activity and name it. Finish. The project will be generated.
A preview pops up with hello world text. Excellent. Time for a test run. Hook up a test device via USB. Go to Run | Edit Configurations… and hit the + for a new configuration. Name it. Set Module to app. Set Deployment Target Options to USB Device. Apply. Cancel. Select the new configuration from the dropdown by the debug button. This is in the upper righthand corner of the window. Hit the debug button. The build takes a minute or so. Give permission to run the app and it pops up on the screen. Note the “rendering problems” report in IntelliJ. Everything looks good on the phone. So far, so good.
Open the MainActivity.java file or whatever the main activity happens to be named. Execute Code | Convert Java File to Kotlin File. The conversion takes a few seconds. Click OK when prompted to correct code in the rest of the project. Add the Kotlin Java runtime with Tools | Kotlin | Configure Kotlin in Project and select OK. Select View | Tool Windows | Gradle and hit the Refresh all Gradle projects button.
Hit the debug button. The app crashes on the phone. Not entirely unexpected. At this point I tried a bunch of things try to get the app to run.
- Did not work. Adding the Kotlin Java runtime again and synchronizing.
- Did not work. File | Invalidate Caches / Restart… followed by Invalidate and Restart.
- Wrong file. Modifying the top level (ProjectName)/build.gradle.
- Almost. Following the official Kotlin with gradle procedure and making changes to (ProjectName)/app/build.gradle.
- Good idea. Change (ProjectName)/app/src/main/java to kotlin.
The problem is that configuring Kotlin with Tools | Kotlin | Configure Kotlin in Project added the libraries to the project, but it did not modify build.gradle like the guide said it would. I could not get any other official instructions to work. What I wound up doing is pulling code out of (ProjectName)/app/build.gradle in a working example project.
My working (ProjectName)/app/build.gradle file looks like this. Your applicationId on line 21 will almost certainly be different.
buildscript ext.kotlin_version = '1.0.0' repositories jcenter() > dependencies classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version" > > apply plugin: 'com.android.application' apply plugin: 'kotlin-android' apply plugin: 'kotlin-android-extensions' android compileSdkVersion 23 buildToolsVersion "23.0.2" defaultConfig applicationId "com.sennue.kotlin_hello_world.kotlinhelloworld" // line 21 minSdkVersion 15 targetSdkVersion 23 versionCode 1 versionName "1.0" > buildTypes release minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' > > //noinspection GroovyAssignabilityCheck sourceSets main.java.srcDirs += 'src/main/kotlin' > > dependencies compile fileTree(dir: 'libs', include: ['*.jar']) testCompile 'junit:junit:4.12' compile 'com.android.support:appcompat-v7:23.1.1' compile 'com.android.support:design:23.1.1' compile "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" >After making the above changes and syncing gradle, the debug build ran again.
Inspecting IntelliJ IDEA-EAP | Preferences… | Plugins indicates the downloadable kotlin-android plugin is obsolete. So far as I can tell, the functionality is baked into IntelliJ IDEA now, but it still needs to be enabled.
I also made the following changes to write a little code in Kotlin. Set text to “Hello, User!”. Uses the name in the user’s profile, if available.
MainActivity.kt
// onCreate val c = application.contentResolver.query(ContactsContract.Profile.CONTENT_URI, null, null, null, null) val username = when (c.count) 0 -> "User" else -> c.moveToFirst() c.getString(c.getColumnIndex("display_name")) > > c.close() val message = findViewById(R.id.message) as TextView message.text = "Hello, $username!"Add permission to read contacts.
AndroidManifest.xml
android:name="android.permission.READ_CONTACTS"/>Add an id to the text view.
content_main.xml
References:
- Android, Building Apps with Over 65K Methods
- Android, check android developer tools version command line
- Android, JetBrains/kotlin-examples/android-mixed-java-kotlin-project/app/build.gradle
- Android, How to use getResource.getIdentifier() to get Layout?
- Android, Get Owner Name of an Android Device
- Android, Trying to write and update contacts
- Android, ContactsContract.Profile
- Android, Content Provider Permissions
- Android, App Manifest
- IntelliJ IDEA 16 EAP
- IntelliJ IDEA, Working with IntelliJ IDEA Features from Command Line
- IntelliJ IDEA, Can’t find “Sync Project with Gradle Files” button in IntelliJ IDEA
- JetBrains
- Kotlin, Statically typed programming language for the JVM, Android and the browser
- Kotlin, Kotlin 1.0 Released: Pragmatic Language for JVM and Android
- Kotlin, Getting Started
- Kotlin, Getting started with Android and Kotlin
- Kotlin, Using Gradle
- Wikipedia, Kotlin (programming language)
IDEs for Kotlin development
JetBrains provides the official Kotlin plugin for two Integrated Development Environments (IDEs): IntelliJ IDEA and Android Studio.
Other IDEs and source editors, such as Eclipse, Visual Studio Code, and Atom, have Kotlin community-supported plugins.
IntelliJ IDEA
IntelliJ IDEA is an IDE for JVM languages designed to maximize developer productivity. It does the routine and repetitive tasks for you by providing clever code completion, static code analysis, and refactorings, and lets you focus on the bright side of software development, making it not only productive but also an enjoyable experience.
Kotlin plugin is bundled with each IntelliJ IDEA release.
Read more about IntelliJ IDEA in the official documentation.
Android Studio
Android Studio is the official IDE for Android app development, based on IntelliJ IDEA. On top of IntelliJ’s powerful code editor and developer tools, Android Studio offers even more features that enhance your productivity when building Android apps.
Kotlin plugin is bundled with each Android Studio release.
Read more about Android Studio in the official documentation.
Eclipse
Eclipse is an IDE that is used to develop applications in different programming languages, including Kotlin. Eclipse also has the Kotlin plugin: originally developed by JetBrains, now the Kotlin plugin is supported by the Kotlin community contributors.
The Kotlin team manages the development and contribution process to the Kotlin plugin for Eclipse. If you want to contribute to the plugin, send a pull request to the Kotlin for Eclipse repository on GitHub.
Compatibility with the Kotlin language versions
For IntelliJ IDEA and Android Studio the Kotlin plugin is bundled with each IDE release. When the new Kotlin version is released, these IDEs will suggest updating Kotlin to the latest version automatically. See the latest supported language version for each IDE in Kotlin releases.
Other IDEs support
JetBrains doesn’t provide the Kotlin plugin for other IDEs. However, some of the other IDEs and source editors, such as Eclipse, Visual Studio Code, and Atom, have their own Kotlin plugins supported by the Kotlin community.
You can use any text editor to write the Kotlin code, but without IDE-related features: code formatting, debugging tools, and so on. To use Kotlin in text editors, you can download the latest Kotlin command-line compiler ( kotlin-compiler-1.9.0.zip ) from Kotlin GitHub Releases and install it manually. Also, you could use package managers, such as Homebrew, SDKMAN!, and Snap package.