Room & RxJava (Kotlin) Sample
The sample app shows an editable user name, stored in the database.
The database is created using Room and has one entity: a
User. Room generates the corresponding SQLite table at
Queries are executed in the
UserDao class. The user retrieval is done via an observable query implemented using a
Flowable. Every time the user data is updated, the Flowable object will emit automatically, allowing to update the UI
based on the latest data. The Flowable will emit only when the query result contains at least a row. When there is no
data to match the query, the Flowable will not emit.
The app has a main Activity that displays the data. The Activity works with a ViewModel to do the following:
- subscribe to the emissions of the user name and updates the UI every time there is a new user name emitted
- notify the ViewModel when the pressed the "Update" and passes the new user name. The ViewModel works with the data source to get and save the data.
Room guarantees that the observable query will be triggered on a background thread. In the Activity, the Flowable events are set to be received on the main thread, so the UI can be updated. The insert query is synchronous so it's wrapped in a Completable and executed on a background thread. On completion, the Activity is notified on the main thread.
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