android - room database connection in Model class android architecture

Question

i'm new in MVVM , i'm using android architecture components too .

this is my code, I'e written the online part and now I'm working on offline part that needs to use the room database .

this is my model class code :

    class CategoryModel(
    private val netManager: NetManager,
    private val sharedPrefManager: SharedPrefManager
) {
    var dateChanges: String = "null";

private lateinit var categoryDao: CategoryDao
private lateinit var dbConnection: DbConnection

fun getCats(): MutableLiveData<MutableList<Cat>> {
    var list = MutableLiveData<MutableList<Cat>>();

    if (netManager.isConnected!!) {
        list = getCatsOnline();
    } else {
        list= getCatsOffline();
    }
    return list
}

this is DbConnection class:

@Database(entities = arrayOf(Cat::class), version = 1)
abstract class DbConnection : RoomDatabase() {
    abstract fun CategoryDao(): CategoryDao

companion object {
    private var INSTANCE: DbConnection? = null

    fun getInstance(context: Context): DbConnection? {
        if (INSTANCE == null) {
            synchronized(DbConnection::class) {
                INSTANCE = Room.databaseBuilder(
                    context.getApplicationContext(),
                    DbConnection::class.java, Const.db_Name
                ).build()
            }
        }
        return INSTANCE
    }

    fun destroyInstance() {
        INSTANCE = null
    }
}

the problem is this , I need to make a connection with room database and it needs the context .

How can I make this connection ? how to access database from Model class ?

score 1 · Accepted Answer · answered Apr 28 '19 at 08:46

Easy way to obtain the Application if you don't want model related to Application,

First implement your own Application

class BaseApp : Application() {
    companion object{
        lateinit var INSTANCE:Application
    }
    override fun onCreate() {
        super.onCreate()
        INSTANCE = this
    }
}

Second use it like:

DbConnection.getInstance(BaseApp.INSTANCE)

Don't forget define the BaseApp in AndroidManifest:

<application
    android:name=".BaseApp"
    ...>
    ...
</application>

android - room database connection in Model class android architecture

1 Answers1