How to fix exception when first buliding Room database in kotlin

Question

I keep on getting this exception when first creating room database

  java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Package.getName()' on a null object reference

This is my room database code:

@Database(entities = [Channel::class], version = 1)
abstract class ChannelRoomDatabase : RoomDatabase() {

    abstract fun channelDao(): ChannelDao

    companion object {
        private var INSTANCE: ChannelRoomDatabase? = null

        fun getInstance(application: Application): ChannelRoomDatabase? {
            if (INSTANCE == null) {

                    INSTANCE = Room.databaseBuilder(application,
                            ChannelRoomDatabase::class.java,
                            "channels")
                            .build()
            }

            return INSTANCE
        }
    }

}

And the gradle code:

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

    def room_version = "1.1.1"

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

Also I get this error when buliding the project:

Execution failed for task ':app:kaptGenerateStubsDebugKotlin'.

Folder /home/Desktop/MySendBird/app/build/generated/source/kaptKotlin/debug


Folder /home/Desktop/MySendBird/app/build/generated/source/kaptKotlin/release


3rd-party Gradle plug-ins may be the cause

What could be the reason? I have seen similar questions here but no any clue. Please help!

Update! In my Dao I get this error

So how to make @Query understand that it I give it a java String not Kotlin String

See also the stacktrace:

/home/Desktop/MySendBird/app/build/tmp/kapt3/stubs/debug/ChannelRoomDatabase.java:6: 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.
public abstract class ChannelRoomDatabase extends android.arch.persistence.room.RoomDatabase {
                ^
:app:compileDebugKotlin
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/repository/ChannelRepository.kt: (16, 13): Variable 'db' is never used
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/repository/ChannelRepository.kt: (47, 23): Parameter 'channel' is never used
w: /home/Desktop/MySendBird/app/src/main/java/com/example/anna/mysendbird/view/MainActivity.kt: (179, 29): Parameter 'userId' is never used

See the similar questions:

using Room with kotlin, get exception when build the database

Null object reference when I try to build room

Can you share code for `ChannelDao` and stack trace in build error?. Stack trace can be found in non graphic mode of build section. — adityakamble49, Jul 13 '18 at 15:06
@adityakamble49 thank you very much for the clue, please see my Dao, it did not showing this error before though, I would notice it for sure — sunflower20, Jul 16 '18 at 09:40
Glad it helped. Can you share code for `ChannelDao` ? Which error it is showing now? — adityakamble49, Jul 16 '18 at 09:43
Looks like lint error, Maybe because of kotlin plugin and kotlin version are different. Try with clean build — adityakamble49, Jul 16 '18 at 09:50
@adityakamble49 very strange behaviour, now I don't get the error in Dao, but get a build error, please see in the new edit — sunflower20, Jul 16 '18 at 10:02
Its build error, can you share stack trace? Stack trace can be found in non graphic mode of build section — adityakamble49, Jul 16 '18 at 10:07
@adityakamble49 build stack trace shows what I have shared already — sunflower20, Jul 16 '18 at 10:15

adityakamble49 · Accepted Answer · 2018-07-16T11:02:05.160

2

You are getting Android Room schema directory error

/home/Desktop/MySendBird/app/build/tmp/kapt3/stubs/debug/ChannelRoomDatabase.java:6: 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.
public abstract class ChannelRoomDatabase extends android.arch.persistence.room.RoomDatabase {

Schema export directory is not provided to the annotation processor

You need to add schema directory to your app's gradle.build as below,

android {

    defaultConfig {
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = ["room.schemaLocation": "$projectDir/schemas".toString()]
            }
        }
    }

}

This will tell your Room annotation processor to generate Database schema and put it under directory mentioned under "room.schemaLocation"

edited Jul 16 '18 at 11:02

answered Jul 16 '18 at 10:48

adityakamble49

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tried but got this: Could not find method javaCompileOptions() for arguments [build_6of96zof7e6pmo2m5c469pv1u$_run_closure1$_closure5@25dac170] on object of type com.android.build.gradle.AppExtension. – sunflower20 Jul 16 '18 at 10:51
btw I first tried this option: exportSchema = false and didn't help – sunflower20 Jul 16 '18 at 10:54
`dependencies { classpath 'com.android.tools.build:gradle:3.1.3' }` – sunflower20 Jul 16 '18 at 11:05
`distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip` – sunflower20 Jul 16 '18 at 11:05
@sunflower20, Versions looks correct. My bad, I have updated location code above, as it should be under `defaultConfig` try it and let me know – adityakamble49 Jul 16 '18 at 11:07
no problem I put it in defaultConfig after, but still the same – sunflower20 Jul 16 '18 at 11:11
Try with clean rebuild – adityakamble49 Jul 16 '18 at 11:11
I just created new Database with new name and the problem resolved!(clean and build didn't help), Thank you very much, you saved me! – sunflower20 Jul 17 '18 at 08:14
Glad it helped :) – adityakamble49 Jul 17 '18 at 09:20

How to fix exception when first buliding Room database in kotlin

1 Answers1