Using Room (With HILT)

Add Dependency

implementation 'androidx.room:room-runtime:2.4.3'
    kapt 'androidx.room:room-compiler:2.4.3'
    implementation 'androidx.room:room-ktx:2.4.3'

Creating Package

클린아키텍처 & Hilt 를 따른다고 가정하고, 다음과 같이 패키지를 만든다

Preparing Entity & DAO & Database

utils → Constants.kt

object Constants {

    const val CONTACTS_TABLE = "contacts_table"
    const val CONTACTS_DATABASE = "contacts_database"

}

db → ContactsEntity.kt

@Entity(tableName = CONTACTS_TABLE)
data class ContactsEntity(
    @PrimaryKey(autoGenerate = true)
    var id: Int = 0,
    var name: String = "",
    var phone: String = "",
)

db → ContactsDao.kt (we will add more Query and function later)

@Dao
interface  ContactsDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun saveContact(contactsEntity: ContactsEntity)

    @Query("SELECT * FROM $CONTACTS_TABLE")
    fun getAllContacts(): Flow<MutableList<ContactsEntity>>


}

db → ContactsDB.kt

@Database(entities = [ContactsEntity::class], 
version = 1, 
exportSchema = false)
abstract class ContactsDB : RoomDatabase() {
    abstract fun contactsDao(): ContactsDao
}

Preparing UI part

각각 item 담당하는 item_contacts.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        app:cardBackgroundColor="@color/white"
        app:cardCornerRadius="5dp"
        app:cardElevation="5dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <TextView
                android:id="@+id/tvName"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:background="@android:color/transparent"
                android:fontFamily="sans-serif-light"
                android:maxLines="1"
                android:padding="8dp"
                android:textColor="@color/black"
                android:textSize="18sp"
                android:textStyle="bold"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                tools:text="Name Contact" />

            <TextView
                android:id="@+id/tvPhone"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:background="@android:color/transparent"
                android:fontFamily="sans-serif-light"
                android:gravity="center"
                android:maxLines="1"
                android:paddingLeft="8dp"
                android:paddingBottom="8dp"
                android:textColor="@color/black"
                android:textSize="14sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@id/tvName"
                tools:ignore="RtlSymmetry"
                tools:text="Phone Number" />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </androidx.cardview.widget.CardView>

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.MainActivity">

    <com.google.android.material.appbar.MaterialToolbar
        android:id="@+id/toolbar"
        android:layout_width="0dp"
        android:layout_height="?attr/actionBarSize"
        android:background="@color/teal_700"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:menu="@menu/menu_toolbar"
        app:subtitle="All your contacts"
        app:subtitleTextColor="#C6FFFFFF"
        app:title="Contacts List"
        app:titleTextColor="@color/white" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/listBody"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginHorizontal="5dp"
        android:visibility="gone"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/toolbar">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/rvContacts"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_marginTop="5dp"
            android:clipToPadding="false"
            android:paddingBottom="50dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/btnShowDialog"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/ic_baseline_person_add_alt_1_24"
        app:backgroundTint="@color/teal_700"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:tint="@color/white"
        tools:ignore="SpeakableTextPresentCheck" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/emptyBody"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginHorizontal="5dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/toolbar">

        <include layout="@layout/empty_list" />

    </androidx.constraintlayout.widget.ConstraintLayout>

    <ProgressBar
        android:id="@+id/loading"
        android:layout_width="30dp"
        android:layout_height="30dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Creating Fragment Dialog

class AddContactFragment : DialogFragment() {
...
}

xml도 만들어줌

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/rounded_win"
    android:padding="15dp"
    tools:context=".ui.add.AddContactFragment">

    <ImageView
        android:id="@+id/imgClose"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:src="@drawable/ic_baseline_clear_24"
        app:layout_constraintBottom_toTopOf="@id/tvTitle"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tvTitle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingHorizontal="32dp"
        android:paddingVertical="8dp"
        android:text="Add your contact infomation"
        android:textColor="#575757"
        android:textSize="16sp"
        app:layout_constraintBottom_toTopOf="@id/edtName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/imgClose" />

    <EditText
        android:id="@+id/edtName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:hint="Name"
        android:maxLines="1"
        android:minHeight="48dp"
        android:padding="10dp"
        android:textColorHint="#009688"
        android:textSize="20sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/tvTitle" />

    <EditText
        android:id="@+id/edtPhone"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:gravity="top"
        android:hint="Phone"
        android:inputType="number"
        android:maxLines="1"
        android:minHeight="48dp"
        android:padding="10dp"
        android:textColorHint="#009688"
        android:textSize="18sp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/edtName" />

    <com.google.android.material.button.MaterialButton
        android:id="@+id/btnSave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:paddingHorizontal="50dp"
        android:text="Save"
        android:textColor="@color/white"
        android:textSize="18sp"
        android:textStyle="bold"
        app:backgroundTint="@color/teal_700"
        app:cornerRadius="10dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/edtPhone" />


</androidx.constraintlayout.widget.ConstraintLayout>

Create Application Class & Module Class

진입점을 지정하는 application

@HiltAndroidApp
class MyApp : Application() { }

진입점 manifest에 지정해줌

<application
    android:name=".MyApp"
    ...
>
...
</application>

di패키지 내에서 db모듈 생성해줌

@Module
@InstallIn(SingletonComponent::class)
object DatabaseModule {

    @Provides
    @Singleton
    fun provideDatabase(@ApplicationContext context: Context) = Room.databaseBuilder(
        context, ContactsDB::class.java, CONTACTS_DATABASE
    ).allowMainThreadQueries()
        .fallbackToDestructiveMigration().build()


    @Provides
    @Singleton
    fun provideDao(db:ContactsDB) = db.contactsDao()


    @Provides
    fun provideEntity()=ContactsEntity()

}

Creating a Repository class

class DatabaseRepository @Inject constructor(private val dao: ContactsDao) {

    suspend fun saveContact(entity : ContactsEntity)=dao.saveContact(entity)
    fun getAllContacts()=dao.getAllContacts()

}

Creating a DataStatus Class

data class DataStatus<out T>(
    val status: Status,
    val data: T? = null,
    val message: String? = null,
    val isEmpty: Boolean? = false
) {

    enum class Status {
        LOADING, SUCCESS, ERROR
    }

    companion object {
        fun <T> loading(): DataStatus<T> {
            return DataStatus(Status.LOADING)
        }

        fun <T> success(data: T? ,isEmpty: Boolean?): DataStatus<T> {
            return DataStatus(Status.SUCCESS, data, isEmpty = isEmpty)
        }

        fun <T> error(error: String): DataStatus<T> {
            return DataStatus(Status.ERROR, message = error)
        }

    }
}

Creating a ViewModel Class

@HiltViewModel
class DatabaseViewModel @Inject constructor(
private val repository: DatabaseRepository
) : ViewModel() {

    private val _contactsList = MutableLiveData<DataStatus<List<ContactsEntity>>>()
    val contactsList : LiveData<DataStatus<List<ContactsEntity>>>
        get() = _contactsList
//뷰모델 외부에 MutableLiveData를 노출하지 않기 위함 -> 캡슐화

    fun saveContact(entity: ContactsEntity) = viewModelScope.launch {
            repository.saveContact(entity)
       
    }

    fun getAllContacts() = viewModelScope.launch {
        _contactsList.postValue(DataStatus.loading())
        repository.getAllContacts()
            .catch { _contactsList.postValue(DataStatus.error(it.message.toString())) }
            .collect { _contactsList.postValue(DataStatus.success(it, it.isEmpty())) }
    }

}

Creating an Adapter

diffCallback과 함께합니다~

@Singleton
class ContactsAdapter @Inject constructor() : RecyclerView.Adapter<ContactsAdapter.ViewHolder>() {

    private lateinit var binding: ItemContactsBinding

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        binding = ItemContactsBinding.inflate(LayoutInflater.from(parent.context), parent, false)
        return ViewHolder()
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.setData(differ.currentList[position])
    }

    override fun getItemCount(): Int {
        return differ.currentList.size
    }

    inner class ViewHolder : RecyclerView.ViewHolder(binding.root) {
        @SuppressLint("SetTextI18n")
        fun setData(item: ContactsEntity) {
            binding.apply {
                tvName.text = item.name
                tvPhone.text = item.phone
            }
        }
    }

    private val differCallback = object : DiffUtil.ItemCallback<ContactsEntity>() {
        override fun areItemsTheSame(oldItem: ContactsEntity, newItem: ContactsEntity): Boolean {
            return oldItem.id == newItem.id
        }

        override fun areContentsTheSame(oldItem: ContactsEntity, newItem: ContactsEntity): Boolean {
            return oldItem == newItem
        }

    }
    val differ = AsyncListDiffer(this, differCallback)

}

Add @AndroidEntryPoint

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
}

프래그먼트에도 entry point 달아줌

@AndroidEntryPoint
class AddContactFragment : DialogFragment() {
...
}

Working Main Activity

필요한거 주입해주기

@Inject
    lateinit var contactsAdapter: ContactsAdapter

    private val viewModel: DatabaseViewModel by viewModels()

@Inject
    lateinit var entity: ContactsEntity

    private val viewModel: DatabaseViewModel by viewModels()

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