MVVM on Android with the Architecture Components

One of the biggest Android news at I/O this year was the Android Architecture Components. Because my very first conference talk back in 2015 was on SQLite Database and Content Provider, I took special interests in the Architecture Components when I heard Room can help eliminate the boiler-plate code in data persistence.

MVVM

Android Architecture Components facilitates the MVVM (Model-View-ViewModel) architecture and this is the first time the Android Framework team officially provides an official guidance on an Android app architecture.

MVVM is not new, and was designed by Microsoft in 2005. Let’s see how this can be implemented on Android with the new Android Architecture Components. I put together (a very much simplified) MVVM diagram with the new components highlighted. Note you can also add another layer between ViewModel and RoomDatabase such as a data Repository class. This diagram only shows data persistence on device. Your app may also fetches data from the network.

Model-View-ViewModel with Android Architecture Components

Implementation steps

Follow these steps to implement MVVM with the new Android Architecture Components in your app:

• Add dependencies in app module build.gradle for architecture components
• Create a entity class, a POJO which also defines database table schema
• Create DAO (Data Access Object), an interface annotated with “@Dao”
• Create database, an abstract class that extends from RoomDatabase
• Create a ViewModel class that contains LiveData, alternatively use RxJava, AsyncTask for the async operations on the SQLite database
• Create UI (Activity & Fragment) and get an instance of ViewModel with ViewModelProviders’ get() method
• Observe the data changes with LiveData (or other async calls), and update UI upon data changes

Update build.gradle

In the app module build.gradle file, add the following dependencies for Room, Lifecycles, LiveData and ViewModel

// Architecture Component - Room
compile "android.arch.persistence.room:runtime:1.0.0-alpha5"
annotationProcessor…