FIT5046 - Week 7: Android Jetpack Room Flashcards

Question 1

What is the Room Persistence Library in Android Jetpack?

Accepted Answer

An abstraction layer over SQLite that provides robust local database access, object mapping, and compile-time query verification.

Question 2

What underlying database system does Room use on Android devices?

Accepted Answer

SQLite, a lightweight relational database management system for permanent local structured data storage.

Question 3

Why is Room preferred over raw SQLite helper classes?

Accepted Answer

Room eliminates boilerplate code, verifies SQL queries at compile time, supports coroutine flows, and integrates seamlessly with Android Architecture Components.

Question 4

What are the four core components of a Room database architecture?

Accepted Answer

Entities (database tables), DAOs (data access objects), RoomDatabase (database instance holder), and Repository (data abstraction layer).

Question 5

What is KSP (Kotlin Symbol Processing) and why is it used with Room?

Accepted Answer

A fast annotation processor that analyzes Kotlin code directly to generate Room database implementation code, replacing the slower kapt tool.

Question 6

Which Gradle dependencies are required to build a Room database with KSP?

Accepted Answer

implementation(libs.androidx.room.runtime), implementation(libs.androidx.room.ktx), and ksp(libs.androidx.room.compiler).

Question 7

Where are Room library version numbers and KSP plugins defined in modern Android projects?

Accepted Answer

In libs.versions.toml (the Gradle Version Catalog file) and applied in project and module build.gradle.kts files.

Question 8

What is a Room Entity?

Accepted Answer

A Kotlin data class annotated with @Entity that maps directly to a table in the underlying SQLite database.

Question 9

How is a table name specified if it differs from the Entity class name?

Accepted Answer

By passing the tableName parameter to the annotation, such as @Entity(tableName = users).

Question 10

How do you customize a column name in a Room Entity?

Accepted Answer

By annotating the data class field with @ColumnInfo(name = custom_column_name).

Question 11

How is a primary key declared in a Room Entity with auto-incrementing IDs?

Accepted Answer

By annotating the ID field with @PrimaryKey(autoGenerate = true) and assigning a default value like val uid: Int = 0.

Question 12

Why should auto-incrementing primary key fields in Kotlin Room entities have a default value of 0?

Accepted Answer

Setting a default value of 0 allows Room to automatically assign a new auto-incremented primary key when inserting a record without requiring a manual ID value.

Question 13

What is a Data Access Object (DAO) in Room?

Accepted Answer

A Kotlin interface annotated with @Dao that defines type-safe methods for inserting, updating, deleting, and querying database records.

Question 14

What are the four primary database operation annotations used in a Room DAO?

Accepted Answer

@Insert, @Update, @Delete, and @Query.

Question 15

How do you pass a Kotlin parameter into a Room @Query SQL string?

Accepted Answer

By placing a colon before the parameter name in the SQL string, such as WHERE id = :enteredId.

Question 16

When are SQL query errors checked in Room @Query methods?

Accepted Answer

At compile time, causing a build failure if column names or SQL syntax are invalid rather than crashing at runtime.

Question 17

Why are DAO write operations (insert, update, delete) declared as coroutine suspend functions?

Accepted Answer

To ensure database write operations execute asynchronously on background threads without blocking the main UI thread.

Question 18

Why do DAO SELECT queries return Flow> instead of a static List?

Accepted Answer

Returning a Flow creates an asynchronous data stream that automatically emits an updated list whenever the underlying database table changes.

Question 19

What is the difference between a Kotlin suspend function and a Kotlin Flow in Room?

Accepted Answer

A suspend function executes once and returns a single value, whereas a Flow emits a continuous stream of sequential values over time.

Question 20

Why is Kotlin Flow described as a cold asynchronous stream?

Accepted Answer

Because it does not execute or emit data until a collector (such as collect or collectAsState) actively starts observing it.

Question 21

What requirements must a class fulfill to serve as a Room Database?

Accepted Answer

It must be an abstract class extending RoomDatabase, annotated with @Database, and contain abstract zero-argument functions returning DAO instances.

Question 22

What parameters are required inside the @Database annotation?

Accepted Answer

entities (an array of entity classes, e.g., [Subject::class]), version (an integer starting at 1), and exportSchema (boolean).

Question 23

Why is exportSchema = false often set in learning projects for Room?

Accepted Answer

It prevents Room from generating schema history files in Gradle folders when database versioning and migrations are not required.

Question 24

Why must a Room Database class implement the Singleton pattern?

Accepted Answer

To ensure only one database instance exists at a time, preventing memory leaks and resource conflicts from opening multiple connections simultaneously.

Question 25

What is the purpose of @Volatile on the database INSTANCE variable?

Accepted Answer

It guarantees that changes made to the database instance by one thread are immediately visible to all other threads, preventing stale reads.

FIT5046 - Week 7: Android Jetpack Room

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