The document discusses Google's Architecture Components, which are a collection of libraries that help handle common tasks in Android development. It covers the main components like Lifecycle, LiveData, ViewModel, and Room. Lifecycle allows activities and fragments to observe lifecycle changes of other objects like LiveData. LiveData is an observable data holder that is lifecycle-aware. ViewModel stores UI-related data to survive configuration changes like screen rotations. Room provides an abstraction layer over SQLite to allow for more robust database access.

1. Extended
Seoul
Architecture Components
alpaca@vcnc.co.kr

2. Speaker
• (@plazgun)
• Between Android Developer

3. Architecture Components
• Google I/O 2017
Architecture Components - Introduction
Architecture Components - Solving the Lifecycle
Architecture Components - Persistence and Offline
•
• https://developer.android.com/topic/libraries/architecture/
index.html

4. Architecture Components
• Handling Lifecycles
• LiveData
• ViewModel
• Room

5. build.gradle
• allprojects {
repositories {
jcenter()
maven { url 'https://maven.google.com' }
}
}
• compile "android.arch.lifecycle:runtime:1.0.0-alpha3"
compile "android.arch.lifecycle:extensions:1.0.0-alpha3"
annotationProcessor "android.arch.lifecycle:compiler:1.0.0-alpha3"
• compile "android.arch.persistence.room:runtime:1.0.0-alpha3"
annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha3"
• compile "android.arch.persistence.room:rxjava2:1.0.0-alpha3"
testCompile "android.arch.persistence.room:testing:1.0.0-alpha3"

6. Handling Lifecycles

7. public class MyActivity extends AppCompatActivity {
private TestListener testListener;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
testListener = new TestListener();
}
@Override
protected void onStart() {
super.onStart();
testListener.start();
}
@Override
protected void onStop() {
super.onStop();
testListener.stop();
}
}

8. public class MyActivity extends AppCompatActivity {
private TestListener testListener;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
testListener = new TestListener();
}
@Override
protected void onStart() {
super.onStart();
testListener.start();
}
@Override
protected void onStop() {
super.onStop();
testListener.stop();
}
}
onStart
Override .

9. Lifecycle .

10. Handling Lifecycles
• Lifecycle
• LifecycleOwner
• LifecycleObserver

11. public class MyActivity extends LifecycleActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_lifecycle);
TestListener testListener = new TestListener(
getLifecycle(),
result -> {
// update UI
});
}
}

12. public class TestListener implements LifecycleObserver {
private Lifecycle lifecycle;
public TestListener(Lifecycle lifecycle, TestCallback callback) {
lifecycle.addObserver(this);
this.lifecycle = lifecycle;
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
void start() {
// start Event
}
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
void clean() {
lifecycle.removeObserver(this);
}
}

13. public class MyActivity extends CustomActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}

14. public class LifecycleActivity extends FragmentActivity
implements LifecycleRegistryOwner {
private final LifecycleRegistry mRegistry
= new LifecycleRegistry(this);
@Override
public LifecycleRegistry getLifecycle() {
return mRegistry;
}
}

15. public class MyActivity extends CustomActivity implements LifecycleRegistryOwner {
private final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this);
@Override
public LifecycleRegistry getLifecycle() {
return lifecycleRegistry;
}
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_lifecycle);
TestListener testListener = new TestListener(getLifecycle(), state -> {
// update Ui
});
}
}

17. public class MyActivity extends LifecycleActivity {
private TestListener testListener;
@Override
protected void onStart() {
super.onStart();
Utils.checkUserStatus(state -> {
if (state.equals("OK")) {
testListener.start();
}
});
}

18. public class MyActivity extends LifecycleActivity {
private TestListener testListener;
@Override
protected void onStart() {
super.onStart();
// ?
Utils.checkUserStatus(state -> {
if (state.equals("OK")) {
testListener.start();
}
});
}

19. StartCreate Resume Pause Stop Destroy
testListener.stop
Utils.checkStatus testListener.start

20. Activity .

21. public class MyActivity extends LifecycleActivity {
private TestListener testListener;
@Override
protected void onStart() {
super.onStart();
Utils.checkUserStatus(state -> {
if (state.equals("OK") && getLifecycle()
.getCurrentState()
.isAtLeast(Lifecycle.State.STARTED)) {
testListener.start();
}
});
}

22. LiveData

23. LiveData
• Observable Data Holder
• Lifecycle aware
• Automatic subscription management

24. LiveData<String> stateData = new MutableLiveData<>();
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
stateData.observe((LifecycleOwner) this, ((String) result) -> {
// stateData .
});
}
@Override
protected void onStart() {
super.onStart();
stateData.setValue(“Start");
}

25. public class StateChangeLiveData extends MutableLiveData<String> {
@Override
protected void onActive() {
super.onActive();
// Active Observer
// Active: Lifecycle.State STARTED RESUMED
}
@Override
protected void onInactive() {
super.onInactive();
// Active Observer
}
}

26. ViewModel

27. public class MyActivity extends LifecycleActivity {
LiveData<User> userData;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
userData = userRepository.fetchData();
userData.observe(this, user -> {
// update UI
});
}
}

28. StartCreate Resume Pause Stop Destroy
Rotated
fetchData
StartCreate Resume
fetchData

29. Activity
.

30. ViewModel
The ViewModel class is designed to store
and manage UI-related data so that the
data survives configuration changes such
as screen rotations.
”
“

31. public class UserViewModel extends ViewModel {
}
public class UserViewModel extends AndroidViewModel {
// Application ViewModel
}

32. ViewModel
•
• ActivityContext
• Resource

33. public class MyActivity extends LifecycleActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.insert_activity);
// ViewModelStore ViewModel .
UserListViewModel viewModel = ViewModelProviders.of(this)
.get(UserListViewModel.class);

34. public class MyActivity extends LifecycleActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ViewModelProviders.of(this).get(UserListViewModel.class)
.getData()
.observe(this, user -> {
//update UI
});
public class UserListViewModel extends ViewModel {
private LiveData<User> userLiveData;
public LiveData<User> getData() {
if (userLiveData == null) {
userLiveData = userRepository.fetchData();
}
return userLiveData;
}
}

35. StartCreate Resume Pause Stop Destroy
Rotated
fetchData
StartCreate Resume
fetchData

36. StartCreate Resume Pause Stop Destroy
Rotated
StartCreate Resume
ViewModel
fetchData
getData getData

37. Room

38. Room
• Sqlite ORM
• Entity
• Dao
• Database

39. id name create_time
@Entity
public class User {
@PrimaryKey(autoGenerate = true)
private Long id;
String name;
@ColumnInfo(name = "created_time")
private long createdTime;
@Ignore
Bitmap profile;
}
Entity

40. DAO
@Dao
public interface UserDao {
@Query("SELECT * FROM user")
List<User> getAll();
@Query("SELECT * FROM user WHERE id IN (:userIds)")
List<User> loadAllByIds(int[] userIds);
@Query("SELECT * FROM user WHERE name LIKE :first LIMIT 1")
User findByName(String first);
@Insert(onConflict = OnConflictStrategy.REPLACE)
void insertAll(User... users);
@Delete
void delete(User user);
@Update
void updateUser(User user);

41. DAO (Rx, LiveData)
@Query("SELECT * FROM user")
LiveData<List<User>> getAllSync();
@Query("SELECT * FROM user WHERE id = :userId")
LiveData<User> fetchUser(String userId);
@Query("SELECT * from user where id = :id LIMIT 1")
Flowable<User> loadUserByIdRx(int id);
@Query("SELECT * FROM user WHERE age > :minAge LIMIT 5")
Cursor loadRawUsersOlderThan(int minAge);

42. Database
@Database(entities = {User.class, Book.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract UserDao userDao();
public abstract BookDao bookDao();
}

43. Entity - Embedded
id name created_time image_id image_width image_height
public class Image {
String id;
Integer width;
Integer height;
}
@Entity
public class User {
@PrimaryKey(autoGenerate = true)
private Long id;
String name;
@Embedded(prefix = "image_")
private Image image;
@ColumnInfo(name = "created_time")
private long createdTime;

44. Entity - TypeConverter
public class User {
@PrimaryKey
private Long id;
@TypeConverters(Converters.class)
private Date date;
public class Converters {
@TypeConverter
public static Date toDate(Long timestamp) {
return timestamp == null ? null :
new Date(timestamp);
}
@TypeConverter
public static Long toTimestamp(Date date) {
return date == null ? null : date.getTime();
}
}

45. Entity - Relation
@Entity(indices = {@Index(value = "id", unique = true)},
foreignKeys = {
@ForeignKey(entity = Book.class,
parentColumns = "id",
childColumns = "bookId",
onDelete = ForeignKey.CASCADE)
})
public class User {
@PrimaryKey(autoGenerate = true)
private Long id;
public Long bookId;
}

46. public class UserDao_Impl implements UserDao {
private final RoomDatabase __db;
private final EntityInsertionAdapter __insertionAdapterOfUser;
private final EntityDeletionOrUpdateAdapter __deletionAdapterOfUser;
private final EntityDeletionOrUpdateAdapter __updateAdapterOfUser;
public UserDao_Impl(RoomDatabase __db) {
this.__db = __db;
this.__insertionAdapterOfUser = new EntityInsertionAdapter<User>(__db) {
@Override
public String createQuery() {
return "INSERT OR REPLACE INTO
`User`(`id`,`name`,`created_time`,`updated_time`,`age`,`bookId`,`image_id`,`image_width`,`image_height`) VALUES
(?,?,?,?,?,?,?,?,?)";
}
@Override
public void bind(SupportSQLiteStatement stmt, User value) {
if (value.getId() == null) {
stmt.bindNull(1);
} else {
stmt.bindLong(1, value.getId());
}
if (value.getName() == null) {
stmt.bindNull(2);
} else {
stmt.bindString(2, value.getName());
}
stmt.bindLong(3, value.getCreatedTime());
if (value.getUpdatedTime() == null) {
stmt.bindNull(4);
} else {
stmt.bindLong(4, value.getUpdatedTime());
}

47. Error
@Query("SELECT * FROM users”)
List<User> getAll();

48. Architecture Components
• Handling Lifecycles
• LiveData
• ViewModel
• Room

49. • RxJava
• greenDAO ( Realm)
• MVP
• Firebase, Retrofit, Dagger, ButterKnife, Fresco, Glide, Mockito …

50. Android Lifecycle Components
vs
ReactiveX

51. public class TestActivity extends RxFragmentActivity {
@Override
protected void onCreate(@Nullable Bundle b) {
super.onCreate(savedInstanceState);
lifecycle()
.filter(e -> e == ActivityEvent.START)
.subscribe(e -> {
// on start
});
}
}
public class TestActivity extends LifecycleActivity
implements LifecycleObserver {
@Override
protected void onCreate(@Nullable Bundle b) {
super.onCreate(savedInstanceState);
getLifecycle().addObserver(this);
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
void start() {
// on start
}
}
LifecycleOwner RxLifecycle

52. public abstract class RxFragmentActivity
extends FragmentActivity
implements LifecycleProvider<ActivityEvent> {
private final BehaviorSubject<ActivityEvent> lifecycleSubject
= BehaviorSubject.create();
@Override
@NonNull
@CheckResult
public final Observable<ActivityEvent> lifecycle() {
return lifecycleSubject.asObservable();
}
@Override
@CallSuper
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
lifecycleSubject.onNext(ActivityEvent.CREATE);
}
@Override
@CallSuper
protected void onStart() {
super.onStart();
lifecycleSubject.onNext(ActivityEvent.START);
}
}
public class LifecycleActivity extends FragmentActivity
implements LifecycleRegistryOwner {
private final LifecycleRegistry mRegistry
= new LifecycleRegistry(this);
@Override
public LifecycleRegistry getLifecycle() {
return mRegistry;
}
}
LifecycleActivity RxFragmentActivity

53. public class TestActivity extends RxFragmentActivity {
@Override
protected void onCreate(@Nullable Bundle b) {
super.onCreate(savedInstanceState);
Flowable<Long> data = getData();
data.compose(RxLifecycle.bindUntilEvent(
lifecycle(), ActivityEvent.DESTROY))
.subscribe(d -> {
// update ui
});
}
}
public class TestActivity extends LifecycleActivity {
@Override
protected void onCreate(@Nullable Bundle b) {
super.onCreate(savedInstanceState);
LiveData<Long> data = getData();
data.observe(this, result -> {
// update ui
});
}
}
LiveData RxFlowable

54. Don’t migrate from RxJava
But be sure that you correctly handle lifecycle.
”
“

55. Room vs greenDAO vs Realm

56. @Entity
public class RoomUser {
@PrimaryKey
private long id;
// getter & setter
}
Room
greenDAO
Realm
@Entity
public class GreenUser {
@Id
private long id;
// getter & setter
}
public class RealmUser extends RealmObject {
@PrimaryKey
private long id;
// getter & setter
}

57. @Entity(tableName = "user")
public class RoomUser {
@ColumnInfo(name = “first_name")
private String firstName;
}
@Entity(nameInDb = "user")
public class GreenUser {
@Property(nameInDb = “first_name")
private String firstName;
}
Room
greenDAO
Realm

58. @Entity(indices = @Index(“address"))
public class RoomUser {
private String address;
@Ignore
private String sessionId;
}
@Entity(indexes = @Index("address DESC"))
public class GreenUser {
private String address;
@Transient
private String sessionId;
}
public class RealmUser extends RealmObject {
@Index
private String address;
@Ignore
private String sessionId;
}
Room
greenDAO
Realm

59. @Dao
public interface RoomUserDao {
@Query("SELECT * FROM RoomUser WHERE id > 10 ORDER BY id DESC”)
List<RoomUser> getUsers();
}
public class GreenUseCase {
public List<GreenUser> getUsers() {
// get DaoSession
return new daoSession.getGreenUserDao().queryBuilder()
.where(GreenUserDao.Properties.Id.gt(10))
.orderDesc(GreenUserDao.Properties.Id)
.list();
}
}
public class RealmUseCase {
public RealmResults<RealmUser> getUsers() {
// get realm instance
return realm.where(RealmUser.class)
.greaterThan("id", 10)
.findAllSorted("id", Sort.DESCENDING);
}
}
Room
greenDAO
Realm

60. public class AndroidUser {
private String userId;
private String groupID;
}
public class AndroidGroup {
private String groupId;
private String groupName;
private List<AndroidUser> roomUser;
}
Relation

61. @Entity
public class RoomGroup {
@PrimaryKey
private long id;
}
@Entity(foreignKeys = @ForeignKey(
entity = RoomGroup.class,
parentColumns = "id",
childColumns = "groupId"))
public class RoomUser {
@PrimaryKey
private long id;
private long groupId;
}
https://developer.android.com/topic/libraries/architecture/room.html#no-object-references
Relation - Room
@Dao
public interface RoomGroupDao {
@Insert(onConflict = OnConflictStrategy.REPLACE)
void insertGroup(RoomGroup group);
@Query("SELECT * FROM RoomGroup WHERE id = :id")
LiveData<RoomGroup> getGroup(long id);
}
@Dao
public interface RoomUserDao {
@Insert(onConflict = OnConflictStrategy.REPLACE)
void insertUsers(List<RoomUser> users);
@Query("SELECT * FROM RoomUser WHERE groupId = :groupId")
LiveData<List<RoomUser>> getUsers(long groupId);
}

62. @Entity
public class GreenGroup {
@Id
private long id;
@ToMany(referencedJoinProperty
= "groupId")
private List<GreenUser> users;
}
@Entity
public class GreenUser {
@Id
private long id;
private long groupId;
}
Relation - greenDAO
public class GreenUseCase {
public void insertGroup(GreenGroup group) {
daoSession.getGreenGroupDao()
.insertOrReplace(group);
daoSession.getGreenUserDao()
.insertOrReplaceInTx(group.getUsers());
}
public GreenGroup getGroup(long groupId) {
return daoSession.getGreenGroupDao()
.queryBuilder()
.where(GreenGroupDao.Properties.Id.eq(groupId))
.build()
.unique();
}
}

63. public class RealmGroup extends RealmObject {
@PrimaryKey
private long id;
RealmList<RealmUser> users;
}
public class RealmUser extends RealmObject {
@PrimaryKey
private long id;
}
Relation - Realm
public class RealmUseCase {
public void insertGroup(RealmGroup group) {
realm.insertOrUpdate(group);
}
public RealmGroup getGroup(long groupId) {
return realm.where(RealmGroup.class)
.equalTo("id", groupId)
.findFirst();
}
}

64. Realm GreenDao Room
Core Native Library SQLite SQLite
Performance Realm Realm
Relation
.
QueryBuilder X
DeepInsert X X
LazyLoading X
Integration Rx Rx, LiveData, Cursor

65. https://youtu.be/FrteWKKVyzI
https://youtu.be/bEKNi1JOrNs
https://youtu.be/MfHsPGQ6bgE
https://developer.android.com/topic/libraries/architecture/index.html
alpaca@vcnc.co.kr

66. • http://engineering.vcnc.co.kr/jobs/