Android Room Persistence library and Kotlin

Question

I am trying to write a simple app using Kotlin and Room Persistence Library. I followed the tutorial in the Android Persistence codelab.

Here is my AppDatabase class in Kotlin:

@Database(entities = arrayOf(User::class), version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userModel(): UserDao

    companion object {
        private var INSTANCE: AppDatabase? = null
        @JvmStatic fun getInMemoryDatabase(context: Context): AppDatabase {
            if (INSTANCE == null) {
                INSTANCE = Room.inMemoryDatabaseBuilder(context.applicationContext, AppDatabase::class.java).allowMainThreadQueries().build()
            }
            return INSTANCE!!
        }

        @JvmStatic fun destroyInstance() {
            INSTANCE = null
        }
    }
}

But when I tried to run the app, it crashes immediately. Here is the crash log:

Caused by: java.lang.RuntimeException: cannot find implementation for com.ttp.kotlin.kotlinsample.room.AppDatabase. AppDatabase_Impl does not exist
    at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90)
    at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:340)
    at com.ttp.kotlin.kotlinsample.room.AppDatabase$Companion.getInMemoryDatabase(AppDatabase.kt:19)
    at com.ttp.kotlin.kotlinsample.MainKotlinActivity.onCreate(MainKotlinActivity.kt:28)
    at android.app.Activity.performCreate(Activity.java:6272)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
    at android.app.ActivityThread.access$900(ActivityThread.java:157) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1356)

It looks like the class AppDatabase_Impl wasn't autogenerated. I checked the original java app downloaded from codelab and found that AppDatabase_Impl was autogenerated.

Kotlin version: 1.1.2-3
Room version: 1.0.0-alpha1

Is there anyone experienced with this?

Edit: Using kapt solves my problem. In my case, I have to replace annotationProcessor with kapt.

Is there `apply plugin: 'kotlin-kapt'` and `kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"` in your module build.gradle ? — Vyacheslav Gerasimov, May 19 '17 at 08:57
@ThanhPham i have same issue but adding kapt introduces some gradle errors, please have a look here https://stackoverflow.com/questions/44142964/room-persistence-lib-implementation-in-kotlin. Can you provide your gradle file? — Sachin Chandil, May 24 '17 at 06:18
@chandil03 I see you just ADD the kapt. In my case, I have to REPLACE the annotationProcessor BY the kapt. — Thanh Pham, May 25 '17 at 07:16

score 53 · Accepted Answer · edited Dec 27 '22 at 00:45

Usually in project build.gradle I define the dependencies versions:

ext {
    buildToolsVersion = '25.0.2'
    supportLibVersion = '25.3.1'
    espressoVersion = '2.2.2'
    archRoomVersion = '1.0.0-alpha1'
}

so in app build.gradle the dependencies look like:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    compile "com.android.support:appcompat-v7:${rootProject.supportLibVersion}"

    compile "android.arch.persistence.room:runtime:${rootProject.archRoomVersion}"
    annotationProcessor "android.arch.persistence.room:compiler:${rootProject.archRoomVersion}"
    kapt "android.arch.persistence.room:compiler:${rootProject.archRoomVersion}"

    androidTestCompile("com.android.support.test.espresso:espresso-core:${rootProject.espressoVersion}", {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    testCompile 'junit:junit:4.12'
}

Now you can define Entities Daos and Database in Kotlin.

Database:

@Database(entities = arrayOf(User::class), version = 1)
abstract class Database : RoomDatabase() {
    abstract fun userDao(): UserDao
}

Entity:

@Entity(tableName = "user")
class User {
    @PrimaryKey(autoGenerate = true)
    var id: Int = 0
    var name: String = ""
}

Dao:

@Dao
interface UserDao {
    @Query("SELECT * FROM user")
    fun getAll(): List<User>

    @Insert
    fun insertAll(vararg users: User)

    @Delete
    fun delete(user: User)
}

NB: Query with parameters. Kotlin renames params, so the SQL query to retrieve all the emails that belong at a user via the userId is:

@Query("SELECT * FROM email "
            + "INNER JOIN user ON user.id = email.userId "
            + "WHERE user.id = :arg0")
    fun getEmailsForUser(userId: Int): List<Email>

Thank for you help. In my case, Kotlin renames params to p0, p1... instead of arg0, arg1... — Thanh Pham, May 22 '17 at 03:06
@Nicola De Fiorenze i have same issue but adding kapt introduces some gradle errors, please have a look here https://stackoverflow.com/questions/44142964/room-persistence-lib-implementation-in-kotlin. — Sachin Chandil, May 24 '17 at 06:22
Also the `apply plugin: 'kotlin-kapt'` is needed in the `build.gradle` file as mentioned in another answer. — shelll, Dec 07 '17 at 14:11

score 39 · Answer 2 · edited May 18 '18 at 15:55

39

In my case, in build.gradle, when you have "annotationProcessor" you need to duplicate with "kapt" and it works.

compile "android.arch.persistence.room:runtime:$room_version"
annotationProcessor "android.arch.persistence.room:compiler:$room_version"
kapt "android.arch.persistence.room:compiler:$room_version"

edited May 18 '18 at 15:55

kodliber

69
1
7

answered May 21 '17 at 10:45

Lyofen

631
6
15

Thank you for your help. – Thanh Pham May 22 '17 at 03:06
@Lyofen i have same issue but adding kapt introduces some gradle errors, please have a look here https://stackoverflow.com/questions/44142964/room-persistence-lib-implementation-in-kotlin. – Sachin Chandil May 24 '17 at 06:24
Thank you very much sir! – Moti Bartov Oct 06 '17 at 13:30

score 12 · Answer 3 · answered Sep 30 '17 at 20:15

Try out these steps

Step 1. Set the room_version in the project.gradle file

buildscript {
    ext.kotlin_version = '1.1.51'
    ext.room_version = '1.0.0-alpha9-1'
...

Step 2. Apply the kotlin-kapt plugin in the app.gradle file, and this solved my issue.

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

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
...

Step 3. Add the kapt dependency in the app.gradle file

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation "android.arch.persistence.room:runtime:$room_version"
    annotationProcessor "android.arch.persistence.room:compiler:$room_version"
    kapt "android.arch.persistence.room:compiler:$room_version"
...
}

score 4 · Answer 4 · answered Aug 14 '17 at 18:01

4

Anyone interested in using Kotlin with Room and Data Binding can see this sample project https://github.com/entrpn/kotlin-room-databinding

answered Aug 14 '17 at 18:01

Juan Acevedo

1,768
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39

j2emanue · Answer 5 · 2018-01-03T07:33:55.617

1

i almost gave up. but after doing just what dharmin007 said i also had to clean the project. that made it work. I've noticed that whenever you add kapt to gradle you MUST clean the project after synching gradle.

edited Jan 03 '18 at 07:33

answered Jan 03 '18 at 07:14

j2emanue

60,549
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score 0 · Answer 6 · answered Feb 02 '19 at 13:47

0

I don't know if there is a necessity to my answer I know that some of the above answers already included this to their answers but they added other things

ONLY ADD apply plugin: 'kotlin-kapt'

answered Feb 02 '19 at 13:47

Mohammad Elsayed

1,885
1
20
46

Android Room Persistence library and Kotlin

6 Answers6

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