Room Persistence lib implementation in Kotlin

Question

I am implementing Room persistence lib in kotlin for my database implementation.

Following are my Entity, Dao and Database classes:

Food.kt

@Entity
class Food(@ColumnInfo(name = "food_name") var foodName: String,
           @ColumnInfo(name = "food_desc") var foodDesc: String,
           @ColumnInfo(name = "protein") var protein: Double,
           @ColumnInfo(name = "carbs") var carbs: Double,
           @ColumnInfo(name = "fat") var fat: Double)
{
    @ColumnInfo(name = "id")
    @PrimaryKey(autoGenerate = true)
    var id: Long = 0
    @ColumnInfo(name = "calories")
    var calories: Double = 0.toDouble()
}

PersonalizedFood.kt

@Entity(primaryKeys = arrayOf("food_id","date"))
class PersonalizedFood(@ColumnInfo(name = "quantity") var quantity: Int,
                       @ColumnInfo(name = "unit") var unit: String,
                       @ColumnInfo(name = "date") var date: Date){

    @ColumnInfo(name = "food_id")
    var foodId:Long = 0
}

FoodDao.kt

@Dao
interface FoodDao {

    companion object{
        const val ID = "id"
        const val NAME = "name"
        const val PROTEIN = "protein"
        const val DESC = "desc"
        const val CARBS = "carbs"
        const val FAT = "fat"

        const val DATE = "date"
        const val FOOD_ID = "food_id"

        const val ALL_FOOD_LIST = "food"
        const val PERSONALISED_FOOD_LIST = "personalised_food"
    }

    /**
     * Returns food details of a food given by food_id
     */
    @Query("SELECT * FROM $ALL_FOOD_LIST WHERE $ID=:food_id")
    fun getFoodDetails(food_id:Long):Food

    /**
     * Inserts food items in all_food_list
     */
    @Insert
    fun addFoodList(list:ArrayList<Food>)

    @Insert(onConflict = REPLACE)
    fun saveFood(food:PersonalizedFood)

    @Query("SELECT * FROM $PERSONALISED_FOOD_LIST WHERE $FOOD_ID=:foodId and $DATE=:date")
    fun getFood(foodId:Int, data:Date):PersonalizedFood

    @Query("SELECT * FROM $ALL_FOOD_LIST where $ID in (select $FOOD_ID from $PERSONALISED_FOOD_LIST where $DATE = :date)")
    fun getFood(date:Date):ArrayList<Food>
}

Converter.kt

class Converter {

    companion object{
        @TypeConverter
        fun fromTimestamp(value: Long?): Date? {
            return if (value == null) null else Date(value)
        }

        @TypeConverter
        fun dateToTimestamp(date: Date): Long {
            return date.time
        }
    }
}

FoodDatabase.kt

@Database(entities = arrayOf(Food::class, PersonalizedFood::class), version = 1)
@TypeConverters(Converter::class)
abstract class FoodDatabase : RoomDatabase(){
    abstract fun foodDao():FoodDao

    companion object{
        private val databaseName = "diet"

        var dbInstance:FoodDao? = null
        fun getInstance(context:Context):FoodDao?{
            if(dbInstance == null)
                dbInstance = Room.inMemoryDatabaseBuilder(context, FoodDatabase::class.java).build().foodDao()
            return dbInstance;
        }
    }
}

And when i run following code to create database:

FoodDatabase.getInstance(baseContext)?.getFood(Calendar.getInstance().time)

It gives me following exception:

Caused by: java.lang.RuntimeException: cannot find implementation for com.chandilsachin.diettracker.database.FoodDatabase. FoodDatabase_Impl does not exist at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:90) at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:340) at com.chandilsachin.diettracker.database.FoodDatabase$Companion.getInstance(FoodDatabase.kt:21) at com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:95) at com.chandilsachin.diettracker.MainActivity$SetUpFoodDatabase.doInBackground(MainActivity.kt:77) at android.os.AsyncTask$2.call(AsyncTask.java:295) at java.util.concurrent.FutureTask.run(FutureTask.java:237) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)  at java.lang.Thread.run(Thread.java:818)

Has anyone implemented room persistence in kotlin?

Edited This question was marked duplicate of this. Though problem statement is same but solution given does not solve my problem. Solution says i have to add replace annotationProcessor to kapt "android.arch.persistence.room:compiler:1.0.0-alpha1" dependency. I made those changes and it resulted in gradle error while project build.

Information:Gradle tasks [:app:assembleDebug] Warning:warning: Supported source version 'RELEASE_7' from annotation processor 'android.arch.persistence.room.RoomProcessor' less than -source '1.8' Warning:warning: The following options were not recognized by any processor: '[kapt.kotlin.generated]' /Users/BBI-M1025/Documents/BBI/Workspace_fun/Android/diet-tracker/app/src/main/java/com/chandilsachin/diettracker/database/Food.kt Error:(1, 1) Some error(s) occurred while processing annotations. Please see the error messages above. Error:Execution failed for task ':app:kaptDebugKotlin'.

Compilation error. See log for more details Information:BUILD FAILED in 10s Information:2 errors Information:2 warnings Information:See complete output in console

I am attaching my gradle file also:

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

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.chandilsachin.diettracker"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    compile 'com.android.support:appcompat-v7:25.0.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.0-alpha8'
    compile 'com.android.support:cardview-v7:25.0.1'
    compile 'com.android.support:recyclerview-v7:25.0.1'
    compile 'com.github.ne1c:rainbowmvp:1.2.1'
    compile "org.jetbrains.anko:anko-commons:0.10.0"

    /*annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1"
    compile "android.arch.lifecycle:extensions:1.0.0-alpha1"
    annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha1"*/

    compile "android.arch.persistence.room:runtime:1.0.0-alpha1"
    annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1"
    kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"

    testCompile 'junit:junit:4.12'
}
repositories {
    mavenCentral()
}

Has anyone come across this issue?

Answer 1

After spinning my head around for a while with this problem, I came across to the solution.

It was really hard as there is no official tutorial, blog etc out there to help with this problem as of now.

I had to do several hit and trial for all the combination of gradle plugins and dependencies as i knew that something is wrong with gradle config only.

Lets come to the solution:

I had to remove apply plugin: 'kotlin-kapt' from build.gradle(:module) file and replace annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha1" to kapt "android.arch.persistence.room:compiler:1.0.0-alpha1".

This is the gradle configuration to successfully compile code.

But there more things to check. You have to initialise properties of your @Entity class unlike java given in Room Persistence lib doc. Though there are getter setter but it is not mentioned to create a constructor with initialisation. So I had to change my @Entity class with this:

@Entity(tableName = "all_food_list")
class Food (@ColumnInfo(name = "food_name") var foodName: String = "",
            @ColumnInfo(name = "food_desc") var foodDesc: String = "",
            @ColumnInfo(name = "protein") var protein: Double = 0.0,
            @ColumnInfo(name = "carbs") var carbs: Double = 0.0,
            @ColumnInfo(name = "fat") var fat: Double = 0.0,
            @ColumnInfo(name = "calories") var calories: Double = 0.0)
{
    @ColumnInfo(name = "id")
    @PrimaryKey(autoGenerate = true)
    var id: Long = 0
}

Now for TypeConverts, Unlike java, you need to create normal function not static functions(companion object):

class Converters{

        @TypeConverter
        fun fromTimestamp(value: String): Calendar {
            val arr = value.split("-")
            val cal = Calendar.getInstance()
            cal.set(arr[0].toInt(), arr[1].toInt(), arr[2].toInt())
            return cal
        }

        @TypeConverter
        fun dateToTimestamp(date: Calendar): String {
            return "${date.get(Calendar.DATE)}-${date.get(Calendar.MONTH)+1}-${date.get(Calendar.YEAR)}"
        }

}

I am adding build.gradle file also to make it more clear:

build.gradle(:project)

buildscript {
    ext.kotlin_version = '1.1.2-4'
    ext.gradle_version_stable = '2.3.2'
    ext.gradle_version_preview = '3.0.0-alpha1'
    ext.anko_version = '0.10.0'
    repositories {
        maven { url 'https://maven.google.com' }
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0-alpha1'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

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

allprojects {
    repositories {
        maven { url 'https://maven.google.com' }
        jcenter()
        maven { url "https://jitpack.io" }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

build.gradle(:module)

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

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.chandilsachin.diettracker"
        minSdkVersion 16
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}


dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    ...
    ...
    // room persistence dependency 
    compile "android.arch.persistence.room:runtime:1.0.0-alpha1"
    kapt "android.arch.persistence.room:compiler:1.0.0-alpha1"

    testCompile 'junit:junit:4.12'
}
repositories {
    mavenCentral()
}

I think this is all, I did to make my code woking.

Hope this helps someone else also.

Answer 2

Here my gradle files, i didn't need to add thoses plugins.

build.gradle(project):

buildscript {
    ext.kotlin_version = '1.1.2-4'
    ext.lifecycle_version = '1.0.0-alpha1'
    ext.room_version = '1.0.0-alpha1'

    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.2'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

    }
}

build.gradle (app)

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

//enable anotation processing with kotlin, disabled by default
kapt {
    generateStubs = true
}


android {
/**
...
**/
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

    //kotlin
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    //support
    compile 'com.android.support:appcompat-v7:25.3.1'

    //google architecture
    compile "android.arch.lifecycle:runtime:$lifecycle_version"
    compile "android.arch.lifecycle:extensions:$lifecycle_version"
    annotationProcessor "android.arch.lifecycle:compiler:$lifecycle_version"
    kapt "android.arch.lifecycle:compiler:$lifecycle_version"

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

}
repositories {
    mavenCentral()
}

Then run menu build-> make project to create impl class. Hope this helps

Answer 3

I made an example similar using Java and used to have same problem and solution was add APT line apt "android.arch.persistence.room:compiler:1.0.0-alpha1"

without apply: apply plugin: 'kotlin-kapt'. Remove this line!!

You have to clear project and rebuild it before run again and try uninstall existing app on phone or Virtual device. Hope you help.

Answer 4

I got the same issue when I try to migrate from Java to Kotlin:

RuntimeException: cannot find implementation for AppDatabase. AppDatabase_Impl does not exist

I tried all these answers in this question, none all them works, then I found an article: Kotlinlang Tutorials - Android Frameworks Using Annotation Processing:

In Kotlin you specify the dependencies in a similar to Java way using Kotlin Annotation processing tool (kapt) instead of annotationProcessor.

Then I modified the build.gradle(Module:app) by changing all annotationProcessor to kapt, it works:

--- a/app/build.gradle
+++ b/app/build.gradle
@@ -2,6 +2,8 @@ apply plugin: 'com.android.application'

 apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-kapt'
 apply plugin: 'kotlin-android-extensions'

 android {
     // Butter Knife
     implementation "com.jakewharton:butterknife:$butterknife_version"
-    annotationProcessor "com.jakewharton:butterknife-compiler:$butterknife_version"
+    kapt "com.jakewharton:butterknife-compiler:$butterknife_version"

     // Room
     implementation "android.arch.persistence.room:runtime:$arch_lifecycle_version"
-    annotationProcessor "android.arch.persistence.room:compiler:$arch_lifecycle_version"
+    kapt "android.arch.persistence.room:compiler:$arch_lifecycle_version"
     // LifeCycle
     implementation "android.arch.lifecycle:runtime:$arch_lifecycle_version"
     implementation "android.arch.lifecycle:extensions:$arch_lifecycle_version"
     implementation "android.arch.lifecycle:common-java8:$arch_lifecycle_version"
-    annotationProcessor "android.arch.lifecycle:compiler:$arch_lifecycle_version"
+    kapt "android.arch.lifecycle:compiler:$arch_lifecycle_version"

     // Dagger
     implementation "com.google.dagger:dagger:$dagger_version"
     implementation "com.google.dagger:dagger-android-support:$dagger_version"
-    annotationProcessor "com.google.dagger:dagger-compiler:$dagger_version"
-    annotationProcessor "com.google.dagger:dagger-android-processor:$dagger_version"
+    kapt "com.google.dagger:dagger-compiler:$dagger_version"
+    kapt "com.google.dagger:dagger-android-processor:$dagger_version"
}

If you use Butter Knife, you should also change to kapt, otherwise the views which are injected might be null.

Answer 5

in the Dao interface check that the annotations like @Query .. are imported from the room database class and not from somewhere else