Beyond Android's Room: Data Persistence

Learn how to make your life easier with data persistence with Android. We will go through entities, migrations, queries, how to handle multi-threading, difference between Room and other Data persistence and finally testing.

There’s always Room for improvement! ;-)

*This was presented in Nairobi, Kenya for the DroidconKE 2019 event

Transcript

1. Naamini Yonazi Software Developer DataVision International Beyond Android's Room: Data Persistence @naaminiyonazi Droidcon KE August 9, 2019
2. 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.
4. 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
5. Good offline experience when the app loses connectivity.
6. WHAT I WAS DOING BEFORE … What happens in Room 1, stays in Room 1 :-)
7. • boilerplate code:
8. • migrations
9. • Testing was chaotic.. • Database operation on the main thread.
10. *ROOM* SOLVED ALL EVERYTHING!
11. 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.
12. Creating a new project Important or this error will occur Android room persistent: AppDatabase_Impl does not exist
13. Room will take care of the creation of the table for you ... NULLABLE Table in your database NON_NULL No column name
14. Crud Operations: • INSERT • UPDATE • DELETE • QUERY (SELECT * FROM Task) Synchronous
15. @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
16. Database/Abstract class... • Update your versions • Annotation: Database and Version • Must extend RoomDatabase
17. 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
19. • Room doesn’t allow you to access the database operations on the main thread … • Async Task can be used
20. remember...Synchronous? Not a good programming practice.. so...
21. 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.
22. 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
23. We like to have our application more user-friendly ...
24. 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:
27. Naamini Yonazi @naaminiyonazi Location naaminicyonazi@gmail.com .naaminicyonazi.com There is always ROOM for improvement!