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.l

Solution 1:

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

Example:

package com.example.app

This will set which package this class belongs to.

Solution 2:

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.

Solution 3:

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