- add dagger 2 dependency injection

app/build.gradle

@@ -30,6 +30,7 @@ android {
 
 dependencies {
     def room_version = "2.2.1"
+    def dagger_version = "2.25.2"
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     // kotlin
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
@@ -50,6 +51,9 @@ dependencies {
     implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0'
     implementation "androidx.lifecycle:lifecycle-runtime:2.1.0"
     kapt "androidx.lifecycle:lifecycle-compiler:2.1.0"
+    // dagger 2
+    api "com.google.dagger:dagger:$dagger_version"
+    kapt "com.google.dagger:dagger-compiler:$dagger_version"
 
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'androidx.test:runner:1.2.0'

app/src/main/java/com/sample/libraryapplication/LibraryApplication.kt

@@ -1,15 +1,24 @@
 package com.sample.libraryapplication
 
 import android.app.Application
+import com.sample.libraryapplication.dagger.components.DaggerLibraryComponent
+import com.sample.libraryapplication.dagger.components.LibraryComponent
+import com.sample.libraryapplication.dagger.modules.AppModule
 
 class LibraryApplication : Application() {
 
     companion object {
         lateinit var instance: LibraryApplication
     }
+    lateinit var libraryComponent: LibraryComponent
 
     override fun onCreate() {
         super.onCreate()
         instance = this
+
+        libraryComponent = DaggerLibraryComponent
+            .builder()
+            .appModule(AppModule(this))
+            .build()
     }
 }

app/src/main/java/com/sample/libraryapplication/dagger/builders/BookListViewModelFactory.kt

@@ -0,0 +1,16 @@
+package com.sample.libraryapplication.dagger.builders
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import com.sample.libraryapplication.repository.BookRepository
+import com.sample.libraryapplication.repository.CategoryRepository
+import com.sample.libraryapplication.viewmodel.BookListViewModel
+import javax.inject.Inject
+
+class BookListViewModelFactory @Inject constructor(private var categoryRepository: CategoryRepository,
+                                                   private var bookRepository: BookRepository) : ViewModelProvider.Factory {
+
+    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
+        return BookListViewModel(categoryRepository, bookRepository) as T
+    }
+}

app/src/main/java/com/sample/libraryapplication/dagger/builders/BookViewModelFactory.kt

@@ -0,0 +1,16 @@
+package com.sample.libraryapplication.dagger.builders
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import com.sample.libraryapplication.repository.BookRepository
+import com.sample.libraryapplication.viewmodel.BookViewModel
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class BookViewModelFactory @Inject constructor(private var bookRepository: BookRepository) : ViewModelProvider.Factory {
+
+    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
+        return BookViewModel(bookRepository)  as T
+    }
+}

app/src/main/java/com/sample/libraryapplication/dagger/components/LibraryComponent.kt

@@ -0,0 +1,15 @@
+package com.sample.libraryapplication.dagger.components
+
+import com.sample.libraryapplication.dagger.modules.AppModule
+import com.sample.libraryapplication.dagger.modules.LibraryModule
+import com.sample.libraryapplication.view.BookActivity
+import com.sample.libraryapplication.view.BookListActivity
+import dagger.Component
+import javax.inject.Singleton
+
+@Singleton
+@Component(modules = [AppModule::class, LibraryModule::class])
+interface LibraryComponent {
+    fun inject(bookActivity: BookActivity)
+    fun inject(bookListActivity: BookListActivity)
+}

app/src/main/java/com/sample/libraryapplication/dagger/modules/AppModule.kt

@@ -0,0 +1,18 @@
+package com.sample.libraryapplication.dagger.modules
+
+import android.app.Application
+import dagger.Module
+import dagger.Provides
+import javax.inject.Singleton
+
+@Module
+class AppModule(application: Application) {
+
+    private var libraryApplication = application
+
+    @Singleton
+    @Provides
+    fun providesApplication(): Application {
+        return libraryApplication
+    }
+}

app/src/main/java/com/sample/libraryapplication/dagger/modules/LibraryModule.kt

@@ -0,0 +1,24 @@
+package com.sample.libraryapplication.dagger.modules
+
+import android.app.Application
+import com.sample.libraryapplication.repository.BookRepository
+import com.sample.libraryapplication.repository.CategoryRepository
+import dagger.Module
+import dagger.Provides
+import javax.inject.Singleton
+
+@Module
+class LibraryModule {
+
+    @Singleton
+    @Provides
+    fun providesBookRepository(application: Application): BookRepository {
+        return BookRepository(application)
+    }
+
+    @Singleton
+    @Provides
+    fun providesCategoryRepository(application: Application): CategoryRepository {
+        return CategoryRepository(application)
+    }
+}

app/src/main/java/com/sample/libraryapplication/database/LibraryDatabase.kt

@@ -1,10 +1,10 @@
 package com.sample.libraryapplication.database
 
+import android.app.Application
 import androidx.room.Database
 import androidx.room.Room
 import androidx.room.RoomDatabase
 import androidx.sqlite.db.SupportSQLiteDatabase
-import com.sample.libraryapplication.LibraryApplication
 import com.sample.libraryapplication.database.dao.BookDAO
 import com.sample.libraryapplication.database.dao.CategoryDAO
 import com.sample.libraryapplication.database.entity.BookEntity
@@ -48,12 +48,12 @@ abstract class LibraryDatabase : RoomDatabase() {
             val book7 = BookEntity(7, "Can I Run?", 99.99, NOVELS_CATEGORY_ID)
             val book8 = BookEntity(8, "Basic of Physics", 10.50, EDUCATIONAL_BOOKS_CATEGORY_ID)
 
-            val categoryDAO = getInstance().getCategoryDAO()
+            val categoryDAO = getInstance(libraryApplication).getCategoryDAO()
             categoryDAO.addCategory(category1)
             categoryDAO.addCategory(category2)
             categoryDAO.addCategory(category3)
 
-            val bookDAO = getInstance().getBookDAO()
+            val bookDAO = getInstance(libraryApplication).getBookDAO()
             bookDAO.addBook(book1)
             bookDAO.addBook(book2)
             bookDAO.addBook(book3)
@@ -64,10 +64,13 @@ abstract class LibraryDatabase : RoomDatabase() {
             bookDAO.addBook(book8)
         }
 
+        private lateinit var libraryApplication: Application
+
         private var instance: LibraryDatabase? = null
-        fun getInstance(): LibraryDatabase {
+        fun getInstance(application: Application): LibraryDatabase {
+            libraryApplication = application
             return if (instance == null) synchronized(this) {
-                instance = Room.databaseBuilder(LibraryApplication.instance, LibraryDatabase::class.java, "library_database")
+                instance = Room.databaseBuilder(application, LibraryDatabase::class.java, "library_database")
                     .fallbackToDestructiveMigration()
                     .addCallback(databaseCallback)
                     .build()

app/src/main/java/com/sample/libraryapplication/repository/BookRepository.kt

@@ -1,5 +1,6 @@
 package com.sample.libraryapplication.repository
 
+import android.app.Application
 import androidx.lifecycle.LiveData
 import com.sample.libraryapplication.database.LibraryDatabase
 import com.sample.libraryapplication.database.dao.BookDAO
@@ -8,9 +9,9 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 
-class BookRepository {
+class BookRepository(application: Application) {
 
-    private var bookDAO: BookDAO = LibraryDatabase.getInstance().getBookDAO()
+    private var bookDAO: BookDAO = LibraryDatabase.getInstance(application).getBookDAO()
 
     fun getBooks(categoryID: Long): LiveData<List<BookEntity>> {
         return bookDAO.getCategoryBooks(categoryID)

app/src/main/java/com/sample/libraryapplication/repository/CategoryRepository.kt

@@ -1,5 +1,6 @@
 package com.sample.libraryapplication.repository
 
+import android.app.Application
 import androidx.lifecycle.LiveData
 import com.sample.libraryapplication.database.LibraryDatabase
 import com.sample.libraryapplication.database.dao.CategoryDAO
@@ -8,9 +9,9 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 
-class CategoryRepository {
+class CategoryRepository(application: Application) {
 
-    private var categoryDAO: CategoryDAO = LibraryDatabase.getInstance().getCategoryDAO()
+    private var categoryDAO: CategoryDAO = LibraryDatabase.getInstance(application).getCategoryDAO()
 
     fun getCategories(): LiveData<List<CategoryEntity>> {
         return categoryDAO.getAllCategories()

app/src/main/java/com/sample/libraryapplication/view/BookActivity.kt

@@ -2,15 +2,16 @@ package com.sample.libraryapplication.view
 
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
-import android.view.View
-import android.widget.Toast
 import androidx.lifecycle.Observer
 import androidx.lifecycle.ViewModelProviders
+import com.sample.libraryapplication.LibraryApplication
 import com.sample.libraryapplication.R
+import com.sample.libraryapplication.dagger.builders.BookViewModelFactory
 import com.sample.libraryapplication.database.entity.BookEntity
 import com.sample.libraryapplication.databinding.ActivityBookBinding
 import com.sample.libraryapplication.viewmodel.BookViewModel
 import kotlinx.android.synthetic.main.activity_book.*
+import javax.inject.Inject
 
 class BookActivity : AppCompatActivity() {
 
@@ -23,10 +24,15 @@ class BookActivity : AppCompatActivity() {
     private var selectedBook: BookEntity? = null
     private var selectedCategoryId: Long? = null
 
+    @Inject
+    lateinit var bookViewModelFactory: BookViewModelFactory
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_book)
 
+        injectDagger()
+
         getIntentExtras()
 
         createViewModel()
@@ -36,6 +42,10 @@ class BookActivity : AppCompatActivity() {
         observeViewModel()
     }
 
+    private fun injectDagger() {
+        LibraryApplication.instance.libraryComponent.inject(this)
+    }
+
     private fun getIntentExtras() {
         if(intent?.extras != null && intent?.extras!!.containsKey("is_update_book"))
             isUpdateBook = intent.getBooleanExtra("is_update_book", false)
@@ -44,7 +54,7 @@ class BookActivity : AppCompatActivity() {
     }
 
     private fun createViewModel() {
-        bookViewModel = ViewModelProviders.of(this)[BookViewModel::class.java]
+        bookViewModel = ViewModelProviders.of(this, bookViewModelFactory)[BookViewModel::class.java]
         bookViewModel.selectedCategoryId = selectedCategoryId
         bookViewModel.selectedBook = selectedBook
         bookViewModel.isUpdateBook = isUpdateBook

app/src/main/java/com/sample/libraryapplication/view/BookListActivity.kt

@@ -13,12 +13,15 @@ import androidx.lifecycle.ViewModelProviders
 import androidx.recyclerview.widget.ItemTouchHelper
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import com.sample.libraryapplication.LibraryApplication
 import com.sample.libraryapplication.R
+import com.sample.libraryapplication.dagger.builders.BookListViewModelFactory
 import com.sample.libraryapplication.database.entity.BookEntity
 import com.sample.libraryapplication.database.entity.CategoryEntity
 import com.sample.libraryapplication.databinding.ActivityBookListBinding
 import com.sample.libraryapplication.viewmodel.BookListViewModel
 import kotlinx.android.synthetic.main.activity_book_list.*
+import javax.inject.Inject
 
 class BookListActivity : AppCompatActivity() {
 
@@ -33,17 +36,30 @@ class BookListActivity : AppCompatActivity() {
     private var booksAdapter: BooksAdapter? = null
     private var selectedCategory: CategoryEntity? = null
 
+    @Inject
+    lateinit var bookListViewModelFactory: BookListViewModelFactory
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
-        bookListViewModel = ViewModelProviders.of(this)[BookListViewModel::class.java]
-        bookListClickHandlers = BookListClickHandlers()
+        injectDagger()
+
+        createViewModel()
 
         setBinding()
 
         observeViewModel(bookListViewModel)
     }
 
+    private fun createViewModel() {
+        bookListViewModel = ViewModelProviders.of(this, bookListViewModelFactory)[BookListViewModel::class.java]
+        bookListClickHandlers = BookListClickHandlers()
+    }
+
+    private fun injectDagger() {
+        LibraryApplication.instance.libraryComponent.inject(this)
+    }
+
     private fun observeViewModel(bookListViewModel: BookListViewModel) {
         bookListViewModel.allCategories.observe(this, Observer { list ->
             if (!isDestroyed) {

app/src/main/java/com/sample/libraryapplication/viewmodel/BookListViewModel.kt

@@ -1,17 +1,13 @@
 package com.sample.libraryapplication.viewmodel
 
-import android.app.Application
-import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.LiveData
+import androidx.lifecycle.ViewModel
 import com.sample.libraryapplication.database.entity.BookEntity
 import com.sample.libraryapplication.database.entity.CategoryEntity
 import com.sample.libraryapplication.repository.BookRepository
 import com.sample.libraryapplication.repository.CategoryRepository
 
-class BookListViewModel(application: Application): AndroidViewModel(application) {
-
-    private var categoryRepository = CategoryRepository()
-    private var bookRepository = BookRepository()
+class BookListViewModel(categoryRepository: CategoryRepository, private var bookRepository: BookRepository) : ViewModel() {
 
     var allCategories: LiveData<List<CategoryEntity>> = categoryRepository.getCategories()
 

app/src/main/java/com/sample/libraryapplication/viewmodel/BookViewModel.kt

@@ -1,14 +1,12 @@
 package com.sample.libraryapplication.viewmodel
 
-import android.app.Application
-import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
 import com.sample.libraryapplication.database.entity.BookEntity
 import com.sample.libraryapplication.repository.BookRepository
 
-class BookViewModel(application: Application) : AndroidViewModel(application) {
+class BookViewModel(private var bookRepository: BookRepository) : ViewModel() {
 
-    private var bookRepository = BookRepository()
     val isBookNameEmpty = MutableLiveData<Boolean>()
     val isBookPriceEmpty = MutableLiveData<Boolean>()
     val shouldFinishActivity = MutableLiveData<Boolean>()

build.gradle

@@ -8,7 +8,7 @@ buildscript {
 
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.1'
+        classpath 'com.android.tools.build:gradle:3.5.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files