'Android room persistent: AppDatabase_Impl does not exist

My app database class

@Database(entities = {Detail.class}, version = Constant.DATABASE_VERSION)
public abstract class AppDatabase extends RoomDatabase {

    private static AppDatabase INSTANCE;

    public abstract FavoritesDao favoritesDao();

    public static AppDatabase getAppDatabase(Context context) {
        if (INSTANCE == null) {
            INSTANCE =
                    Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, Constant.DATABASE).allowMainThreadQueries().build();

                    //Room.inMemoryDatabaseBuilder(context.getApplicationContext(),AppDatabase.class).allowMainThreadQueries().build();
        }
        return INSTANCE;
    }

    public static void destroyInstance() {
        INSTANCE = null;
    }
}

Gradle lib:

 compile "android.arch.persistence.room:runtime:+"   
 annotationProcessor "android.arch.persistence.room:compiler:+"

And when i ask for instance it will give this error, AppDatabase_Impl does not exist in my application class

public class APp extends Application {

    private boolean appRunning = false;

    @Override
    public void onCreate() {
        super.onCreate();
        AppDatabase.getAppDatabase(this); //--AppDatabase_Impl does not exist

    }   

}

Solution 1:^[1]

For those working with Kotlin, try changing annotationProcessor to kapt in the apps build.gradle

for example:

// Extensions = ViewModel + LiveData
implementation "android.arch.lifecycle:extensions:1.1.0"
kapt "android.arch.lifecycle:compiler:1.1.0"
// Room
implementation "android.arch.persistence.room:runtime:1.0.0"
kapt "android.arch.persistence.room:compiler:1.0.0"

also remember to add this plugin

apply plugin: 'kotlin-kapt'

to the top of the app level build.gradle file and do a clean and rebuild (according to https://codelabs.developers.google.com/codelabs/android-room-with-a-view/#6)

In Android Studio, if you get errors when you paste code or during the build process, select Build >Clean Project. Then select Build > Rebuild Project, and then build again.

UPDATE

If you have migrated to androidx

def room_version = "2.3.0" // check latest version from docs

implementation "androidx.room:room-runtime:$room_version"
kapt "androidx.room:room-compiler:$room_version"

UPDATE 2 (since July 2021)

def room_version = "2.3.0" // check latest version from docs

implementation "androidx.room:room-ktx:$room_version"
kapt "androidx.room:room-compiler:$room_version"

Solution 2:^[2]

Just use

apply plugin: 'kotlin-kapt'

in app build.gradle

And keep both in dependencies

annotationProcessor "android.arch.persistence.room:compiler:$rootProject.roomVersion"
kapt "android.arch.persistence.room:compiler:$rootProject.roomVersion"

EDIT

In newer version don't need to add both dependencies at a time Just use, hope it will work.

kapt 'android.arch.persistence.room:compiler:1.1.1'

Solution 3:^[3]

I had this error when I missed

@Database(entity="{<model.class>})

Ensure that the entity model specified in the annotation above refers to the particular model class and also ensure that the necessary annotation:

@Entity(tableName = "<table_name>" ...)

is properly defined and you'd be good

Solution 4:^[4]

if you are using kotlin classes to implement database then use

apply plugin: 'kotlin-kapt'

and

kapt "android.arch.persistence.room:compiler:1.1.1"

in your gradle file, it will work.

Solution 5:^[5]

For Kotlin Developers

Use this:

implementation "android.arch.persistence.room:runtime:1.0.0"
kapt "android.arch.persistence.room:compiler:1.0.0"

And add apply plugin: 'kotlin-kapt' to the top of the app level build.gradle.

For Java Developers

implementation "android.arch.persistence.room:runtime:1.0.0"
annotationProcessor "android.arch.persistence.room:compiler:1.0.0"

Solution 6:^[6]

It is not just about updating your dependencies. Make sure all your Room dependencies have the same version.

implementation 'android.arch.persistence.room:rxjava2:1.1.0-alpha2'
implementation 'android.arch.persistence.room:runtime:1.1.0-alpha2'
annotationProcessor "android.arch.persistence.room:compiler:1.1.0-alpha2"

In the sample snippet above, all my Room dependencies have the same version 1.1.0-alpha2

Solution 7:^[7]

I meet with the problem, because I forget @Dao annotation

@Dao
public interface SearchHistoryDao {
    @Query("SELECT * FROM search_history")
    List<SearchHistory> getAll();

    @Insert
    void insertAll(SearchHistory... histories);

    @Delete()
    void delete(SearchHistory history);
}

Room Official tutorial

Solution 8:^[8]

make sure to add correct dependency for room in build.gradle

ext {
   roomVersion = '2.1.0-alpha06'
}

// Room components
implementation "androidx.room:room-runtime:$rootProject.roomVersion"
implementation "androidx.room:room-ktx:$rootProject.roomVersion"
kapt "androidx.room:room-compiler:$rootProject.roomVersion"
androidTestImplementation "androidx.room:room-testing:$rootProject.roomVersion"

And below line at the top-

apply plugin: 'kotlin-kapt'

Solution 9:^[9]

I met this problem because I have forgotten the apt dependences

implementation "android.arch.lifecycle:extensions:$archLifecycleVersion"
implementation "android.arch.persistence.room:runtime:$archRoomVersion"
annotationProcessor "android.arch.lifecycle:compiler:$archLifecycleVersion"
annotationProcessor "android.arch.persistence.room:compiler:$archRoomVersion"

after added the annotationProcessor, and rebuild it, the problem solved.

Solution 10:^[10]

Had the same problem. Implemented the few classes and interface as officially told in a new example project created by Android Studio: https://developer.android.com/training/data-storage/room/

All mentioned solutions above did not help, the necessary _Impl files according to my database class were not generated by Room. Finally executing gradle clean build in terminal gave me the hint that lead to the solution:

"warning: Schema export directory is not provided to the annotation processor so we cannot export the schema. You can either provide room.schemaLocation annotation processor argument OR set exportSchema to false."

I added the parameter exportSchema = false in the database class

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

And then it worked, found these two generated files in the app module under generatedJava:

AppDatabase_Impl
UserDao_Impl

I don't understand this behaviour as the parameter is said to be optional, see https://stackoverflow.com/a/44645943/3258117

Solution 11:^[11]

The question is pretty old, but I've stumbled on this today and none of the provided answers helped me. Finally I managed to resolve it by noticing that google documentation actually is still adopted to Java and not Kotlin by default, actually they have added a comment which I've ignored

For Kotlin use kapt instead of annotationProcessor

So, instead of

annotationProcessor "androidx.room:room-compiler:$room_version"

If you are developing with Kotlin, you should use:

    kapt "androidx.room:room-compiler:$room_version"

Solution 12:^[12]

If you are using kotlin, add kotlin annotation processor plugin to app level build.gradle

plugins {
    id "org.jetbrains.kotlin.kapt"
}

Also remove annotationProcessor and replace it with kapt

Instead of

dependencies {
    def room_version = "2.3.0"
    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"
}

dependencies {
    def room_version = "2.3.0"
    implementation "androidx.room:room-runtime:$room_version"
    kapt "androidx.room:room-compiler:$room_version"
}

The annotationProcessor only works in java environment. The kapt takes care of both java and kotlin. If something wrong with your implementation, those plugins will show them at the compile time.

Solution 13:^[13]

In my kotlin app, I just added the following line at the top of my build.gradle file :

apply plugin: 'kotlin-kapt'

And the following line in the dependencies section:

kapt "androidx.room:room-compiler:2.2.5"

I hope it fixes your issue.

Solution 14:^[14]

Agreed with the above answers

The solution is as below. Change annotationProcessor to kapt as below

// annotationProcessor "androidx.room:room-compiler:$room_version"
implementation "androidx.room:room-runtime:$room_version"
kapt "androidx.room:room-compiler:$room_version"

Solution 15:^[15]

In my case, I was testing the connectivity for room database and I have put the testing class inside the directory which I have created inside the AndroidTest folder. I have moved it out of the custom directory, then it worked pretty well.

Solution 16:^[16]

The same phenomenon occurred to me.

following

implementation "android.arch.persistence.room:runtime:1.1.1"

Adding causes another build error but tracks the cause from the log.

In my case, there was an error in the SQL implementation. After fixing, the build was successful.

So you may want to check the implementation of the entire room library instead of looking at the crashed locals.

Solution 17:^[17]

Use the following gradle link:

compile 'android.arch.persistence.room:runtime:1.0.0-alpha9'
annotationProcessor 'android.arch.persistence.room:compiler:1.0.0-alpha9'

You need to create a different singleton class and get the AppDatabase from there like this:

RoomDB.java

public class RoomDB {

private static RoomDB INSTANCE;

public static AppDatabase getInstance(Context context) {
    if (INSTANCE == null) {
        INSTANCE =
                Room.databaseBuilder(context.getApplicationContext(), AppDatabase.class, Constant.DATABASE).allowMainThreadQueries().build();

                //Room.inMemoryDatabaseBuilder(context.getApplicationContext(),AppDatabase.class).allowMainThreadQueries().build();
    }
    return INSTANCE;
}

public static void destroyInstance() {
    INSTANCE = null;
}

App.java

public class App extends Application {

private boolean appRunning = false;

@Override
public void onCreate() {
    super.onCreate();
    RoomDB.getInstance(this); //This will provide AppDatabase Instance
}

Solution 18:^[18]

The issue is more around the correct library that is not included in the gradle build. I had a similar issue and added the missing

testImplementation "android.arch.persistence.room:testing:$room_version

Solution 19:^[19]

Changing the dependencies in my gradle file did'nt help me in fixing the error.I had missed this Database annotation in class where Room database was initialized which was causing this issue.

@Database(entities = [UserModel::class], version = 1)

Ensure that the entity model specified in the annotation above refers to the particular model class

Solution 20:^[20]

For Kotlin Developers

if you checked Dao and Entity and also used Kapt and there is no problem, I guess there is a problem with your kotlin version if you are using kotlin 1.4 and above. update Room to last version from this link.

2.3.0-alpha03 solved my problem.

Solution 21:^[21]

For me, the Android Studio automatically updated dependencies as soon as you include any of the Room database related imports. But as per https://developer.android.com/jetpack/androidx/releases/room#declaring_dependencies you need to update few. Here is how my code-base looks like:

AppDatabase.kt

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase

@Database(entities = arrayOf(MyEntity::class), version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun myDAO(): MyDAO

    companion object {
        @Volatile private var instance: AppDatabase? = null
        private val LOCK = Any()

        operator fun invoke(context: Context)= instance ?: synchronized(LOCK){
            instance ?: buildDatabase(context).also { instance = it}
        }

        private fun buildDatabase(context: Context) = Room.databaseBuilder(context,
            AppDatabase::class.java, "db-name.db")
            .build()
    }
}

Update the build.gradle as specified in one of the answers:

apply plugin: 'kotlin-kapt' // this goes with other declared plugin at top
dependencies { // add/update the following in dependencies section
    implementation 'androidx.room:room-runtime:2.2.3'
//    annotationProcessor 'androidx.room:room-compiler:2.2.3' // remove this and use the following
    kapt "androidx.room:room-compiler:2.2.3"

}

Sync the gradle and you should be good to go.

Solution 22:^[22]

In addition to missing

annotationProcessor "android.arch.persistence.room:compiler:x.x.x"

I had also missed adding the below annotation in my class

@Entity(tableName = "mytablename")

Solution 23:^[23]

Reading the example here: Room Example

I fixed this error just using the correct (I guess it is) annotationProcessorFile, as follows:

annotationProcessor "android.arch.persistence.room:compiler:<latest_version>"

Also, I upgraded to 2.2.0 either in Room Version as in Lifecycle version.

Once synchronized the graddle, I could start working with Room.

So, Good luck! And let the code be with you!

Solution 24:^[24]

Not in the case of OP, but this also happens when you mistakenly use implementation instead of annotationProcessor like this:

implementation "android.arch.persistence.room:compiler:x.x.x"

Instead of this:

annotationProcessor "android.arch.persistence.room:compiler:x.x.x"

Solution 25:^[25]

Just in case anyone out there should make the same mistake as I did, don't call your database class "Database" or you'll get the same error.

Solution 26:^[26]

Nothing works from above answers and I noticed that the issue persists for me when I'm using room version2.3.0 or 2.4.2. However, 2.5.0-alpha01 version works well when I applied it.

build.gradle:app

def roomVersion = '2.5.0-alpha01'
implementation "androidx.room:room-ktx:$roomVersion"
kapt "androidx.room:room-compiler:$roomVersion"
testImplementation "android.arch.persistence.room:testing:$roomVersion"

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	nayriz
Solution 2
Solution 3	Thadeus Ajayi
Solution 4	navalkishoreb
Solution 5	Pedro Massango
Solution 6	Idee
Solution 7	duyuanchao
Solution 8	Deepak
Solution 9	ahsiu
Solution 10
Solution 11	Pavel
Solution 12	UdaraWanasinghe
Solution 13	ZakariaBK
Solution 14	Arunabh Das
Solution 15	Farruh Habibullaev
Solution 16	user11221761
Solution 17	Amine Karimi
Solution 18	Saurabh Sharma
Solution 19	Wajhia Maqsood
Solution 20	hamid Mahmoodi
Solution 21	Rujoota Shah
Solution 22	Meenohara
Solution 23	Anibal Itriago
Solution 24	artenson.art98
Solution 25	J. O. A. Rayner-Hilles
Solution 26	zekromWex

'Android room persistent: AppDatabase_Impl does not exist

Solution 1:[1]

UPDATE

UPDATE 2 (since July 2021)

Solution 2:[2]

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