some optimisation and migrate to kotlin

app/build.gradle

@@ -1,4 +1,7 @@
 apply plugin: 'com.android.application'
+apply plugin: 'com.google.gms.google-services'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
 
 android {
     compileSdkVersion 28
@@ -100,10 +103,10 @@ dependencies {
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 
     //shimmer effect
-
     implementation 'com.facebook.shimmer:shimmer:0.5.0'
-}
 
-apply plugin: 'com.google.gms.google-services'
-apply plugin: 'kotlin-android'
-apply plugin: 'kotlin-android-extensions'
+    // navigations
+    def navigationVersion = "2.3.0"
+    implementation "androidx.navigation:navigation-fragment-ktx:$navigationVersion"
+    implementation "androidx.navigation:navigation-ui-ktx:$navigationVersion"
+}

app/src/main/java/govind/iiitl/app/BloggerAPI.kt

@@ -0,0 +1,30 @@
+package govind.iiitl.app
+
+import govind.iiitl.app.models.PostList
+import retrofit2.Call
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+import retrofit2.http.GET
+
+internal object BloggerAPI {
+    private const val key = "AIzaSyBpfJGq4L8xoKsue_jhXHtWLYlvwcMoREs"
+    private const val url = "https://www.googleapis.com/blogger/v3/blogs/5429117628766351084/posts/"
+    private var postService: PostService? = null
+    @JvmStatic
+    val service: PostService?
+        get() {
+            if (postService == null) {
+                val retrofit = Retrofit.Builder()
+                        .baseUrl(url)
+                        .addConverterFactory(GsonConverterFactory.create())
+                        .build()
+                postService = retrofit.create(PostService::class.java)
+            }
+            return postService
+        }
+
+    interface PostService {
+        @get:GET("?key=$key")
+        val postList: Call<PostList?>?
+    }
+}