Android Room Persistence library and Kotlin
Anyone interested in using Kotlin with Room and Data Binding can see this sample project https://github.com/entrpn/kotlin-room-databinding
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 an 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>
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:$room_version"
Try out these steps
Step 1. Set the room_version
in the project.gradle
file
buildscript {
ext.kotlin_version = '1.1.51'
ext.room_version = '1.0.0-alpha9-1'
...
Step 2. Apply the kotlin-kapt
plugin in the app.gradle
file, and this solved my issue.
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'
android {
compileSdkVersion 26
buildToolsVersion "26.0.1"
...
Step 3. Add the kapt
dependency in the app.gradle
file
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation "android.arch.persistence.room:runtime:$room_version"
annotationProcessor "android.arch.persistence.room:compiler:$room_version"
kapt "android.arch.persistence.room:compiler:$room_version"
...
}