Why Room

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Goal

Understand why local persistence is critical and how Room compares to raw SQLite.

Prerequisites

• Intermediate tier completed (ViewModel + repository + Navigation Compose)

The persistence problem

The intermediate app fetches from a public API every time. This means:

• No offline access
• Slow startup (network fetch before any content)
• No user data persistence (favorites, bookmarks)

Why Room

Room is Google's recommended persistence layer on Android. It wraps SQLite and provides:

• Compile-time SQL verification — no runtime SQL syntax errors
• Kotlin coroutines + Flow — DAO methods are suspend or return Flow
• Automatic migration — schema changes are declarative
• No boilerplate — an annotation processor generates the implementation

Raw SQLite (SQLiteOpenHelper) requires manual cursor management, ContentValues, and raw SQL strings. Room handles all of that.

Gradle setup

// build.gradle.kts (app module)
plugins {
    id("com.google.devtools.ksp") version "2.0.21-1.0.28"
}

android {
    // ...
}

dependencies {
    val roomVersion = "2.6.1"
    implementation("androidx.room:room-runtime:$roomVersion")
    implementation("androidx.room:room-ktx:$roomVersion")
    ksp("androidx.room:room-compiler:$roomVersion")
}

Checkpoint

./gradlew app:build  # or build in Android Studio
# BUILD SUCCESSFUL — Room compiler generates code

Next: Add Room — define entities, DAOs, and wire into the repository.