Android Architecture components

GDG DevFest Mediterranean 2017 Cap. II
Mike Trizio
@mik3lantoni0 #nerdipity

Mike Trizio - @mik3lantoni0 - #nerdipity
Michelantonio Trizio
GDG Bari community lead
Computer Science Engineer
Android Dev
CTO @ Wideverse

SPOILER ALERT

About architecture components
➔ Announced at Google I/O 2017
➔ Provide frameworks to create more maintainable and robust app
➔ Encourage decoupled components within the app

What’s the problem?

The solution
Follow architectural principle
➔ Separation of concerns
➔ Drive your UI from a model (preferably persistent one)

App architecture

SEASON 1
1x01 - Room
1x02 - Lifecycle
1x03 - ViewModel
1x04 - LiveData
1x05 - Paging

1x01 - Room

Data layer before Room

Room architecture diagram

Components of room
@Entity: annotation needed define a table
@Dao: annotation needed define a Data Access Object
@Database: annotation to create the database holder

Create an entity
@Entity(tableName = "characters")
class Character {
@PrimaryKey (autoGenerate = true)
public int id;
public String firstName;
public String lastName;
@Ignore // Tells Room to ignore
this field
Bitmap picture;
}
id (PK) firstName LastName
1 Walter White
2 Jesse Pinkman
3 Gustavo Fring
character table

Create a Dao
Annotations available
@Dao
@Insert
@Delete
@Update
@Query
@Dao // Required annotation for Dao to be
recognized by Room
public interface CharacterDao {
// Returns a list of all users in the db
@Query("SELECT * FROM characters")
List<User> getAll();
// Inserts multiple users
@Insert
void insertAll(Character... characters);
// Deletes a single character
@Delete
void delete(Character character);
}

Create the Database
@Database(entities = {Character.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
private static AppDatabase sInstance;
public abstract CharacterDao characterDao(); //Getters for Dao
public static AppDatabase getInstance(Context context) {
if (sInstance == null) {
sInstance = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "database-name").build();
}
return sInstance;
}
}

Query examples (1)
@Query("SELECT * FROM character WHERE first_name LIKE :first AND last_name
LIKE :last LIMIT 1")
Character findByName(String first, String last);
@Query("SELECT series.id, series.title, series.description, category.name as
categoryName FROM series LEFT JOIN category ON series.category_id =
category.id")
List<CategorySerie> getCategorySeries();

Query examples (2)
@Query("SELECT series.id, series.title, series.description, category.name as
categoryName FROM series LEFT JOIN category ON series.category_id =
category.id where series.id = :seriesId")
CategorySerie getCategorySerie(long seriesId);

get and use Database instance
//GET DATABASE INSTANCE
AppDatabase database = AppDatabase.getInstance(Context context);
//GET ALL CHARACTERS INTO THE DB
List<Character> allCharacters = database.characterDao().getAll();

Migration (1)
@Database(entities = {Character.class}, version = 2) //update the version
public abstract class AppDatabase extends RoomDatabase {
private static SunshineDatabase sInstance;
public abstract CharacterDao characterDao();
public static AppDatabase getInstance(Context context) {
if (sInstance == null) {
sInstance = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "database-name").build();
}
return sInstance;
}
}

Migration (2)
@Entity(tableName = "character")
class Character {
@PrimaryKey (autoGenerate = true)
public int id;
public String firstName;
public String lastName;
public String alias; //add the alias field
@Ignore // Tells Room to ignore this field
Bitmap picture;
}

Migration (3)
Room.databaseBuilder(getApplicationContext(), MyDb.class,
"database-name").addMigrations(MIGRATION_1_2).build();
static final Migration MIGRATION_1_2 = new Migration(1, 2) {
@Override
public void migrate(SupportSQLiteDatabase database) {
database.execSQL("ALTER TABLE character add column alias text");
}
}

1x02 - Lifecycle

Android activity lifecycle

going upside down... or simply rotate the phone

...a lot of stranger things can happen

public class MyObserver implements LifecycleObserver {
@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
public void onResume() {
}
@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
public void onPause() {
}
}
aLifecycleOwner.getLifecycle().addObserver(new MyObserver());
Lifecycle observer implementation

observable events
ON_CREATE ON_DESTROY ON_PAUSE
ON_RESUME ON_START ON_STOP

LifecycleOwner
public class MyActivity extends LifecycleActivity {
private MyObeserver myObeserver;
public void onCreate(...) {
myObeserver = new MyObeserver(this, getLifecycle(), location ->{
// update UI
});
}
}

1x03 - ViewModel

ViewModels persist configuration change

Interaction of entities in an app built with
Architecture components

public class CharacterDetailViewModel extends ViewModel {
private CharacterEntry mCharacter;
public DetailActivityViewModel(CharacterDao dao, int characterId) {
mCharacter = dao.getDetails(id);
}
public CharacterEntry getCharacter(){
return mCharacter;
}
}
Create a viewModel (1)

Create a viewModel (2)
public class DetailActivity extends LifecycleActivity{
@Override
protected void onCreate(Bundle savedInstanceState){
CharacterModelFactory characterFactory =
new CharacterModelFactory(dao, characterId);
characterViewModel = ViewModelProviders.of(this,
characterModelFacotry).get(CharacterDetailViewModel.class);
}
}

1x04 - LiveData

DING DING DING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

LiveData example
MutableLiveData<String> name = new
MutableLiveData<String>();
name.setValue("Saul");
name.observe(<LIFECYCLE OWNER>,
newName -> {
// Do something when the
observer is triggered; usually
updating the UI
});

merge liveData and viewModel
public CharacterDetailViewModel(){
mCharacter = new
MutableLiveData<>();
}
mViewModel.getCharacter().observe(
this, characterEntry -> {
// Update the UI
});
if (characterEntry != null)
bindWeatherToUI(characterEntry);

Add a new character live

1x05 - Paging

when we deal with a lot of data….

Paging library workflow (mainly in background)

➔ KeyDatasource
➔ TiledDataSource
@Query("select * from users WHERE age
> :age order by name DESC, id ASC")
TiledDataSource<User>
usersOlderThan(int age);
Datasource

PagedList
➔ Loads data from Datasource
➔ You can configure how much data is
loaded and how much data should be
prefetched
➔ Can provide update signals to other
classes

PagedListAdapter
➔ Implementation of RecyclerView.Adapter
➔ Presents data from PagedList
➔ use a background thread to compute
changes from PagedList

LivePagedListProvider
@Query("SELECT * from users order
WHERE age > :age order by name DESC,
id ASC")
public abstract
LivePagedListProvider<Integer, User>
usersOlderThan(int age);

Recap
1. Room - provide simple interaction with database
2. Lifecycle - better dealing with Activity Lifecycle
3. ViewModel - way to hold and manage data
4. LiveData - data holder lifecycle aware that allow to observe data
5. Paging - easy and light way to load information as needed

what’s next?
Architecture components guide
https://goo.gl/j5Zztk
Architecture talk @ GDD Krakow 2017
https://goo.gl/6C2fvr
Architecture guide codelab
https://goo.gl/gF9Vyu

That’s all folks!!!

Questions?

Thank you!
Rate this talk please
https://goo.gl/TDT5Hb
Follow me
@mik3lantoni0

Android Architecture components

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