Part 10: Adding Dagger 2

app/build.gradle

@@ -23,7 +23,9 @@ android {
         main.java.srcDirs += 'src/main/kotlin'
     }
 }
-
+kapt {
+    generateStubs = true
+}
 dependencies {
     compile fileTree(dir: 'libs', include: ['*.jar'])
     testCompile 'junit:junit:4.12'
@@ -42,6 +44,11 @@ dependencies {
     compile 'com.squareup.retrofit2:retrofit:2.0.0'
     compile 'com.squareup.retrofit2:converter-moshi:2.0.0'
 
+    // Dagger 2
+    compile 'com.google.dagger:dagger:2.4'
+    kapt 'com.google.dagger:dagger-compiler:2.4'
+    provided 'org.glassfish:javax.annotation:10.0-b28'
+
     // Tests
     testCompile 'org.mockito:mockito-core:1.+'
     testCompile 'org.jetbrains.spek:spek:1.0.+'

app/src/main/AndroidManifest.xml

@@ -2,9 +2,10 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.droidcba.kedditbysteps">
 
-    <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.INTERNET" />
 
     <application
+        android:name=".KedditApp"
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"

app/src/main/java/com/droidcba/kedditbysteps/KedditApp.kt

@@ -0,0 +1,25 @@
+package com.droidcba.kedditbysteps
+
+import android.app.Application
+import com.droidcba.kedditbysteps.di.AppModule
+import com.droidcba.kedditbysteps.di.news.DaggerNewsComponent
+import com.droidcba.kedditbysteps.di.news.NewsComponent
+
+/**
+ *
+ * @author juancho.
+ */
+class KedditApp : Application() {
+
+    companion object {
+        lateinit var newsComponent: NewsComponent
+    }
+
+    override fun onCreate() {
+        super.onCreate()
+        newsComponent = DaggerNewsComponent.builder()
+                .appModule(AppModule(this))
+                //.newsModule(NewsModule()) Module with empty constructor is implicitly created by dagger.
+                .build()
+    }
+}

app/src/main/java/com/droidcba/kedditbysteps/api/NewsRestAPI.kt

@@ -1,23 +1,11 @@
 package com.droidcba.kedditbysteps.api
 
 import retrofit2.Call
-import retrofit2.Retrofit
-import retrofit2.converter.moshi.MoshiConverterFactory
+import javax.inject.Inject
 
-class NewsRestAPI() : NewsAPI {
-
-    private val redditApi: RedditApi
-
-    init {
-        val retrofit = Retrofit.Builder()
-                .baseUrl("https://www.reddit.com")
-                .addConverterFactory(MoshiConverterFactory.create())
-                .build()
-
-        redditApi = retrofit.create(RedditApi::class.java)
-    }
+class NewsRestAPI @Inject constructor(private val redditApi: RedditApi) : NewsAPI {
 
     override fun getNews(after: String, limit: String): Call<RedditNewsResponse> {
         return redditApi.getTop(after, limit)
     }
-}
+}

app/src/main/java/com/droidcba/kedditbysteps/di/AppModule.kt

@@ -0,0 +1,27 @@
+package com.droidcba.kedditbysteps.di
+
+import android.content.Context
+import com.droidcba.kedditbysteps.KedditApp
+import dagger.Module
+import dagger.Provides
+import javax.inject.Singleton
+
+/**
+ *
+ * @author juancho.
+ */
+@Module
+class AppModule(val app: KedditApp) {
+
+    @Provides
+    @Singleton
+    fun provideContext(): Context {
+        return app;
+    }
+
+    @Provides
+    @Singleton
+    fun provideApplication(): KedditApp {
+        return app;
+    }
+}

app/src/main/java/com/droidcba/kedditbysteps/di/NetworkModule.kt

@@ -0,0 +1,24 @@
+package com.droidcba.kedditbysteps.di
+
+import dagger.Module
+import dagger.Provides
+import retrofit2.Retrofit
+import retrofit2.converter.moshi.MoshiConverterFactory
+import javax.inject.Singleton
+
+/**
+ *
+ * @author juancho.
+ */
+@Module
+class NetworkModule {
+
+    @Provides
+    @Singleton
+    fun provideRetrofit(): Retrofit {
+        return Retrofit.Builder()
+                .baseUrl("https://www.reddit.com")
+                .addConverterFactory(MoshiConverterFactory.create())
+                .build()
+    }
+}

app/src/main/java/com/droidcba/kedditbysteps/di/news/NewsComponent.kt

@@ -0,0 +1,23 @@
+package com.droidcba.kedditbysteps.di.news
+
+import com.droidcba.kedditbysteps.di.AppModule
+import com.droidcba.kedditbysteps.di.NetworkModule
+import com.droidcba.kedditbysteps.features.news.NewsFragment
+import dagger.Component
+import javax.inject.Singleton
+
+/**
+ *
+ * @author juancho.
+ */
+@Singleton
+@Component(modules = arrayOf(
+        AppModule::class,
+        NewsModule::class,
+        NetworkModule::class)
+)
+interface NewsComponent {
+
+    fun inject(newsFragment: NewsFragment)
+
+}

app/src/main/java/com/droidcba/kedditbysteps/di/news/NewsModule.kt

@@ -0,0 +1,34 @@
+package com.droidcba.kedditbysteps.di.news
+
+import com.droidcba.kedditbysteps.api.NewsAPI
+import com.droidcba.kedditbysteps.api.NewsRestAPI
+import com.droidcba.kedditbysteps.api.RedditApi
+import dagger.Module
+import dagger.Provides
+import retrofit2.Retrofit
+import javax.inject.Singleton
+
+/**
+ *
+ * @author juancho.
+ */
+@Module
+class NewsModule {
+
+    @Provides
+    @Singleton
+    fun provideNewsAPI(redditApi: RedditApi): NewsAPI {
+        return NewsRestAPI(redditApi)
+    }
+
+    @Provides
+    @Singleton
+    fun provideRedditApi(retrofit: Retrofit): RedditApi {
+        return retrofit.create(RedditApi::class.java)
+    }
+
+    /**
+     * NewsManager is automatically provided by Dagger as we set the @Inject annotation in the
+     * constructor, so we can avoid adding a 'provider method' here.
+     */
+}

app/src/main/java/com/droidcba/kedditbysteps/features/news/NewsFragment.kt

@@ -6,6 +6,7 @@ import android.support.v7.widget.LinearLayoutManager
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import com.droidcba.kedditbysteps.KedditApp
 import com.droidcba.kedditbysteps.R
 import com.droidcba.kedditbysteps.commons.InfiniteScrollListener
 import com.droidcba.kedditbysteps.commons.RedditNews
@@ -15,15 +16,21 @@ import com.droidcba.kedditbysteps.features.news.adapter.NewsAdapter
 import kotlinx.android.synthetic.main.news_fragment.*
 import rx.android.schedulers.AndroidSchedulers
 import rx.schedulers.Schedulers
+import javax.inject.Inject
 
 class NewsFragment : RxBaseFragment() {
 
     companion object {
         private val KEY_REDDIT_NEWS = "redditNews"
     }
 
+    @Inject lateinit var newsManager: NewsManager
     private var redditNews: RedditNews? = null
-    private val newsManager by lazy { NewsManager() }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        KedditApp.newsComponent.inject(this)
+    }
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
         return container?.inflate(R.layout.news_fragment)
@@ -60,9 +67,9 @@ class NewsFragment : RxBaseFragment() {
 
     private fun requestNews() {
         /**
-         * first time will send empty string for after parameter.
+         * first time will send empty string for 'after' parameter.
          * Next time we will have redditNews set with the next page to
-         * navigate with the after param.
+         * navigate with the 'after' param.
          */
         val subscription = newsManager.getNews(redditNews?.after ?: "")
                 .subscribeOn(Schedulers.io())

app/src/main/java/com/droidcba/kedditbysteps/features/news/NewsManager.kt

@@ -1,17 +1,19 @@
 package com.droidcba.kedditbysteps.features.news
 
 import com.droidcba.kedditbysteps.api.NewsAPI
-import com.droidcba.kedditbysteps.api.NewsRestAPI
 import com.droidcba.kedditbysteps.commons.RedditNews
 import com.droidcba.kedditbysteps.commons.RedditNewsItem
 import rx.Observable
+import javax.inject.Inject
+import javax.inject.Singleton
 
 /**
  * News Manager allows you to request news from Reddit API.
  *
  * @author juancho
  */
-class NewsManager(private val api: NewsAPI = NewsRestAPI()) {
+@Singleton
+class NewsManager @Inject constructor(private val api: NewsAPI) {
 
     /**
      *