Android Architecture Components LifeCycle , LiveData , Room and ViewModel 

Agenda ● What is Architecture ? ● Common Problems ● Why to use Android Architecture Components ? ● LifeCycle ● ViewModel ● LiveData ● Room 

What is Architecture ? Software application architecture is the process of defining a structured solution that meets all of the technical and operational requirements, while optimizing common quality attributes such as performance, security, and manageability. It involves a series of decisions based on a wide range of factors, and each of these decisions can have considerable impact on the quality, performance, maintainability, and overall success of the application 

What is Architecture ? 

What is Architecture ? Separation of Concerns 

Common Developer Problems ● Multiple Entry Point ● Constantly Switching Flow and Tasks ● Screen Rotation 

Architecture Patterns ● MVC (Model-View-Controller) ● MVP (Model-View-Presenter) ● MVVM (Model-View-ViewModel) ● VP (View-Presenter) 

Our Expectations 

Reality 

Why Architecture Components ? Persist Data Manage LifeCycle Modular Defense Against Common Errors Less Boilerplate 

Simple App App UI/UX ROOM Modifies,requests or generates data for database Response Back LIVE DATA 

Components 4. Room 1. LifeCycle 2. LiveData 3. ViewModel 

Dependencies //Room compile 'android.arch.persistence.room:runtime:1.0.0' annotationProcessor 'android.arch.persistence.room:compiler:1.0.0' //LifeCycle and ViewModel compile 'android.arch.lifecycle:runtime:1.0.0' compile 'android.arch.lifecycle:extensions:1.0.0' annotationProcessor 'android.arch.lifecycle:compiler:1.0.0' 

LifeCycle : Problems 2. Untimely UI updates 1. Activity/Fragment LifeCycle 4. Screen Rotation 3. Broadcast Receivers 

LifeCycle LifeCycle Owner : LifeCycle Owner are the objects with lifecycle ,like Activities and Fragments LifeCycle Owners: ( Activities/Fragments ) LifeCycle Observer : LifeCycle Observer observe LifeCycleOwners , and are notifies of lifecycle changes LifeCycle Observer (Ex: LiveData) 

LifeCycle @Override public void onCreate(...) { myLocationListener = new MyLocationListener(this, location -> { // update UI }); } @Override public void onStart() { super.onStart(); myLocationListener.start(); } @Override public void onStop() { super.onStop(); myLocationListener.stop(); } 

LifeCycle @Override public void onCreate(...) { myLocationListener = new MyLocationListener(this, location -> { // update UI }); } @Override public void onStop() { super.onStop(); myLocationListener.stop(); } @Override public void onStart() { super.onStart(); Util.checkUserStatus(result -> { // what if this callback is invoked AFTER activity is stopped? if (result) { myLocationListener.start(); } }); } 

MyLocationListener public class MyLocationListner implements LifecycleObserver { } //Add this our MainActivity getLifecycle().addObserver(new MyLocationListner()); @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) public void connectListener() { ... } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) public void disconnectListener() { ... } 

MyLocationListener class MyLocationListener implements LifecycleObserver { } private boolean enabled = false; public MyLocationListener(Context context, Lifecycle lifecycle, Callback callback) { ... } public void enable() { enabled = true; if (lifecycle.getCurrentState().isAtLeast(STARTED)) { // connect if not connected } } @OnLifecycleEvent(Lifecycle.Event.ON_STOP) void stop() { // disconnect if connected } @OnLifecycleEvent(Lifecycle.Event.ON_START) void start() { if (enabled) { // connect } } 

MainActivity class MainActivity extends AppCompatActivity { private MyLocationListener myLocationListener; public void onCreate(...) { } } myLocationListener = new MyLocationListener(this,getLifecycle(),location -> { // update UI }); Util.checkUserStatus(result -> { if (result) { myLocationListener.enable(); } }); 

LifeCycle : Use Cases 2. Stopping and starting video buffering 1. Location updates 3. Pausing and resuming animatable drawables 

ViewModel The ViewModel class is designed store and manage UI-related data so that data survives the configuration changes such as screen rotations ViewModel: public class MyViewModel extends ViewModel{ } AndroidViewModel with context: public class MyViewModel extends AndroidViewModel { public MyViewModel(@NonNull Application application) { super(application); } } 

ViewModel LifeCycle 

Create ViewModel public class MyViewModel extends ViewModel { private int mRotationCount; public int getRotationCount() { mRotationCount = mRotationCount + 1; return mRotationCount; } } 

Implement ViewModel @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } //Get view model instance MyViewModel myViewModel = ViewModelProviders.of(this).get(MyViewModel.class); //set the increment value mRotationCountTextView.setText("" + myViewModel.getRotationCount()); 

Context ViewModel public class MyViewModel extends AndroidViewModel { private NotificationManager mNotificationManager; } public MyViewModel(@NonNull Application application) { super(application); mNotificationManager = (NotificationManager) application. getSystemService(Context.NOTIFICATION_SERVICE); } 

ViewModel : Use Cases 2. Shared between fragments 1. Retain State 3. Replacing loaders 

LiveData 1. LiveData is observable data holder. 2. It notifies the observers when data changes so that you can update the UI. 3. It is also Life Cycle Aware 

LiveData : Pros 1. UI Matches your data state 2. No Memory leak 3. No more manual lifecycle handling 

Create LiveData Object public class NameViewModel extends ViewModel { // Rest of the ViewModel... } // Create a LiveData with a String private MutableLiveData mCurrentName; public MutableLiveData getCurrentName() { if (mCurrentName == null) { mCurrentName = new MutableLiveData(); } return mCurrentName; } 

Observe LiveData Objects private NameViewModel mModel; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); } // Get the ViewModel. mModel = ViewModelProviders.of(this).get(NameViewModel.class); // Create the observer which updates the UI. final Observer nameObserver = new Observer() { @Override public void onChanged(@Nullable final String newName) { // Update the UI, in this case, a TextView. mNameTextView.setText(newName); } }; // Observe the LiveData, passing in this activity as the // LifecycleOwner and the observer. mModel.getCurrentName().observe(this, nameObserver); 

Update LiveData Objects mButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { String anotherName = "John Doe"; mModel.getCurrentName().setValue(anotherName); } }); 

Database ?? 

Room Room is a robust SQL Object Mapping Library 

Plain Old Java Object (POJO) Old POJO Room POJO public class User { private int uid; private String firstName; private String lastName; private int age; private Date dateOfJoining; } public class User { private int uid; private String firstName; private String lastName; private int age; private Date dateOfJoining; } @PrimaryKey(autoGenerate = true) @ColumnInfo(name = "first_name") @Entity @ColumnInfo(name = "last_name") 

UserDao.java public interface UserDao { } @Insert void insertAll(List users); @Delete void delete(User user); @Update void updateUser(User user); @Query("SELECT * FROM user") List getAll(); @Dao @Query("SELECT * FROM user WHERE uid = :userID") User findUserById(int userID); 

UserDao.java public interface UserDao { } @Insert void insertAll(List users); @Delete void delete(User user); @Update void updateUser(User user); @Query("SELECT * FROM user") LiveData> getAll(); @Dao @Query("SELECT * FROM user WHERE uid = :userID") User findUserById(int userID); 

Setup Room Database public abstract class AppDatabase extends RoomDatabase { } public abstract UserDao userDao(); @Database(entities = {User.class}, version = 1) @TypeConverters({Converters.class}) 

Build Room Database public class AppController extends Application { private static AppController appController; private AppDatabase appDatabase; @Override public void onCreate() { super.onCreate(); appController = this; } public static AppDatabase getAppDatabase() { return appController.appDatabase; } } //Initialize the room database with database name appDatabase = Room.databaseBuilder(this, AppDatabase.class, "user-database") .fallbackToDestructiveMigration() .build(); 

Display data public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); List userList = AppController .getAppDatabase() .userDao() .getAll(); //Update List in adapter } } 

UserModel public class UserModel extends ViewModel { private final UserDao userDao; public UserModel() { userDao = AppController .getAppDatabase() .userDao(); } public LiveData> getAllUser() { return userDao.getAll(); } } 

MainActivity public class MainActivity extends AppCompatActivity { private UserModel userModel; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //Setup your UI } } userModel = ViewModelProviders.of(this).get(UserModel.class); userModel.getAllUser().observe(this, new Observer>() { @Override public void onChanged(@Nullable List userList) { // updateUI } }); 

Thank you burhanrashid52 Burhanuddin Rashid Resources : ● Android Architecture Components : http://bit.ly/2hGRxoc ● Exploring Architecture Components : http://bit.ly/2j1Pvvv Multidots Inc. https://www.multidots.com/