Naamini Yonazi Software Developer DataVision International Beyond Android's Room: Data Persistence @naaminiyonazi Droidcon KE August 9, 2019

Room? - Android Architecture Component - Google IO, 2017 - Is an (another) ORM solution for the Android developers. - Library provides an abstraction layer over SQLite, robust, full power of SQLite. - Quickly create sqlite databases and perform CRUD operations Others most popular ones are probably ORMLite, GreenDAO and DbFlow.

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Why Room? ● Since Room works on SQL, you can write your query easily. ● You can use LiveData with Room in a few steps. ● The library takes up only 50KB. ● Room also provides easy migration mechanism which is fully tested

Good offline experience when the app loses connectivity.

WHAT I WAS DOING BEFORE … What happens in Room 1, stays in Room 1 :-)

● boilerplate code:

● migrations

● Testing was chaotic.. ● Database operation on the main thread.

*ROOM* SOLVED ALL EVERYTHING!

Room’s Components Three main Components (annotated class): 1. Entity - creating database table/class 2. DAO - Data Access Object used to access data from the database; has methods..It is an interface 3. Database: It is an abstract class where we define our db. Extends RoomDatabase.

Creating a new project Important or this error will occur Android room persistent: AppDatabase_Impl does not exist

Room will take care of the creation of the table for you ... NULLABLE Table in your database NON_NULL No column name

Crud Operations: ● INSERT ● UPDATE ● DELETE ● QUERY (SELECT * FROM Task) Synchronous

@Dao ● To access your data using room’s persistence database, you need to work with @Dao ● They offer abstract access to your apps database ● Dao can be an interface/abstract

Database/Abstract class... ● Update your versions ● Annotation: Database and Version ● Must extend RoomDatabase

Database/Abstract class... ● Create your DB with the Db Builder ● Specify db name Main access point underlying connection to your app’s persisted and relational data

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● Room doesn’t allow you to access the database operations on the main thread … ● Async Task can be used

remember...Synchronous? Not a good programming practice.. so...

Migrations.. java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you’ve changed schema but forgot to update the version number. You can simply fix this by increasing the version number. java.lang.IllegalStateException: A migration from 1 to 2 is necessary. Please provide a Migration in the builder or call fallbackToDestructiveMigration in the builder in which case Room will re-create all of the tables.

Now Room doesn’t know how to migrate database from version 1 to version 2. In this error Room suggest us two solutions: ● drop and recreate the whole database ● upgrade existing database schema to the newer version

We like to have our application more user-friendly ...

android { javaCompileOptions { annotationProcessorOptions { arguments = ["room.schemaLocation": "$projectDir/schemas".toString()] } } } } Thanks to this code fragment added to build.gradle file we’ll be able to get those auto-generated by Room SQL statements and use them to make a migration:

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Naamini Yonazi @naaminiyonazi Location [email protected] .naaminicyonazi.com There is always ROOM for improvement!