Lesson 22: Local Storage: Introduction to Room Database

Local Storage: Introduction to Room Database

Right now, close the app and your tasks vanish — everything lives only in memory. Room gives you a real local database with almost no boilerplate.

Add the dependencies

implementation("androidx.room:room-runtime:2.6.1")
implementation("androidx.room:room-ktx:2.6.1")
ksp("androidx.room:room-compiler:2.6.1")

(You'll need the KSP plugin applied at the top of your build.gradle.kts — Android Studio will prompt you to add it.)

Define your table with an Entity

@Entity(tableName = "tasks")
data class TaskEntity(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    val title: String,
    val isDone: Boolean
)

Define your queries with a DAO

@Dao
interface TaskDao {
    @Query("SELECT * FROM tasks")
    fun getAllTasks(): Flow>

    @Insert
    suspend fun insertTask(task: TaskEntity)

    @Update
    suspend fun updateTask(task: TaskEntity)
}

DAO stands for Data Access Object — it's the only place SQL-like queries live in your whole app. Notice getAllTasks() returns a Flow — this means the UI automatically gets updated data any time the underlying table changes, with zero manual refresh code needed.

Tie it together with a Database class

@Database(entities = [TaskEntity::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun taskDao(): TaskDao
}

Creating the database instance

val db = Room.databaseBuilder(
    context,
    AppDatabase::class.java,
    "task-database"
).build()

You'd typically create this once, at app startup, and pass it down to wherever it's needed — we'll wire this into the ViewModel properly in the next lesson.

Next: Lesson 23 — combining Room with ViewModel so tasks genuinely persist.