Room database setup in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a Room entity with a primary key.

Android Kotlin

import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity
 data class User(
    @PrimaryKey val [1]: Int,
    val name: String
)

Drag options to blanks, or click blank then click option'

Aid

BuserId

Cuid

Dkey

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field name that is not declared in the data class.

Forgetting to annotate the primary key.

The primary key field is commonly named id to uniquely identify each entity.

2fill in blank

medium

Complete the code to create a DAO interface with a query to get all users.

Android Kotlin

import androidx.room.Dao
import androidx.room.Query

@Dao
interface UserDao {
    @Query("SELECT * FROM user")
    fun [1](): List<User>
}

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AgetAllUsers

BfetchUsers

CloadAll

DretrieveUsers

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names that do not match the query purpose.

Omitting the return type.

The method name getAllUsers clearly describes the action of fetching all user records.

3fill in blank

hard

Fix the error in the Room database abstract class declaration.

Android Kotlin

import androidx.room.Database
import androidx.room.RoomDatabase

@Database(entities = [User::class], version = 1)
abstract class AppDatabase : [1]() {
    abstract fun userDao(): UserDao
}

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ADatabaseBuilder

BDatabase

CRoomBuilder

DRoomDatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect superclass names.

Forgetting to make the class abstract.

The Room database class must extend RoomDatabase to work properly.

4fill in blank

hard

Fill both blanks to build the Room database instance in a singleton pattern.

Android Kotlin

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

object DatabaseBuilder {
    private var INSTANCE: AppDatabase? = null

    fun getInstance(context: Context): AppDatabase {
        if (INSTANCE == null) {
            INSTANCE = Room.[1](context.applicationContext, AppDatabase::class.java, "app_db").[2]()
        }
        return INSTANCE!!
    }
}

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AdatabaseBuilder

Bbuild

Ccreate

Dinitialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names for building the database.

Not calling build() to finalize the database instance.

The method databaseBuilder starts building the database, and build() finalizes the creation.

5fill in blank

hard

Fill all three blanks to define an entity with an auto-generated primary key and a non-null column.

Android Kotlin

import androidx.room.Entity
import androidx.room.PrimaryKey
import androidx.room.ColumnInfo

@Entity
 data class Product(
    @PrimaryKey(autoGenerate = [1]) val id: Int = 0,
    @ColumnInfo(name = "product_name") val [2]: String,
    val price: Double = [3]
)

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

Cname

D0.0

Attempts:

3 left

💡 Hint

Common Mistakes

Setting autoGenerate to false or missing it.

Using wrong field names.

Not providing a default value for price.

Setting autoGenerate = true enables automatic ID generation. The product name field is named name. The price defaults to 0.0.