CODEWITHSUNDEEP
androidkotlinandroid-room
Jéwôm'
Jéwôm'

Reputation: 3971

Null object reference when I try to build room

I want to build room in Kotlin using my function getDatabase(context) and I have this error :

W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference
W/System.err:     at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:77)

This is very strange because it's the first time I have this error (I use Room in other project and I don't have this bug). The app don't crash but the database is not working.

I try looking in internet but I don't see nothing about this bug (only this japanese guy : https://teratail.com/questions/118177 but I don't understand japanese).

AppDatabase :

@Database(entities = [(Wallet::class), (Historique::class)], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun walletDao(): WalletDao
    abstract fun historiqueDao(): HistoriqueDao
}

private var INSTANCE: AppDatabase? = null

fun getDatabase(context: Context?): AppDatabase {
    if (INSTANCE == null)
        INSTANCE = context?.let { Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME).build() }
    return INSTANCE as AppDatabase
}

This is my Gradle :

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

android {
    compileSdkVersion 27
    defaultConfig {
        applicationId "my.app"
        minSdkVersion 19
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'com.android.support:support-v4:27.1.1'

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

    implementation "org.jetbrains.anko:anko-commons:0.10.4"
    implementation "org.jetbrains.anko:anko-design:0.10.4"
    implementation "com.chibatching.kotpref:kotpref:2.5.0"
    implementation "com.chibatching.kotpref:initializer:2.5.0"
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
}

Upvotes: 5

Views: 2772

Answers (3)

Jeprox
Jeprox

Reputation: 101

I encountered the same problem. The simple solution is to go to your database class and check if the package is set at the top of the file.

Example:

package com.example.app

This will set which package this class belongs to.

Upvotes: 10

svope
svope

Reputation: 31

I had the same problem, thanks to @Jéwôm', the link he provided - https://teratail.com/questions/118177 and Google Translator I found a solution.

That japanese guy whom Jéwôm' mentioned found out that this bug occured because of damaged/wrong directory structure in project files.

His directory seemed like this:

app  
   |-manifests  
   |-java  
     |-com.example.user.applyName
       |-MainActivity
       |-SubActivity // インスタンスを生成するActivity
     |-AppDatabase
     |-Dairy
     |-DairyDao
    |-res

And he solved the problem by moving files "AppDatabase", "Dairy" and "DairyDao" to the same folder as "MainActivity" and "SubActivity".

In my case I didn't have badly structured directory structure, but I moved all kotlin files to other folder (in my case from "com.example.myAppName" to "com.example.myAppName (androidTest)" and then moved them back (back to "com.example.myAppName"). Then I rebuilt that project. This somehow worked for me.

Upvotes: 1

Jéwôm'
Jéwôm'

Reputation: 3971

The problem was from some imports (by coping the class from an other project).

Upvotes: 0

Related Questions