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Modern Android App Development with Java

Room Database

Discover how to implement Room database for offline support in your Travel Blog app. Learn to define entities, create DAOs, and build a database with Room annotations. This lesson guides you to efficiently store and manage app data locally while understanding best practices like singleton patterns.

We'll cover the following...

Dependencies #

To use the Room database, we need to add it to our dependencies list:

Scheme
dependencies {
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.0.0'
    implementation 'com.google.android.material:material:1.1.0-alpha10'
    implementation 'com.github.bumptech.glide:glide:4.10.0'
    implementation 'com.squareup.okhttp3:okhttp:4.2.1'
    implementation 'com.google.code.gson:gson:2.8.6'
    def room_version = "2.2.3"
    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"
}

Because Room database heavily relies on custom annotations, we also added Room annotationProcessor dependency.

Entities #

Now, we need to tell Room what entities we want to save to the database. Let’s open the Blog class and add the @Entity annotation (1). Doing so, we tell the Room to create a table for the blog entity.

To define a primary key we can simply use @PrimaryKey annotation on the id field (2). While the Room library can automatically persist all Java primitives, it can’t persist custom objects, like Author. To save ...