VocabularyFragment is started from MainActivity after retrieving Firestore data

app/src/main/java/com/paktalin/vocabularynotebook/firestoreitems/Vocabulary.kt

@@ -2,6 +2,7 @@ package com.paktalin.vocabularynotebook.firestoreitems
 
 class Vocabulary {
     var pojo:Pojo
+    private lateinit var words:MutableList<WordItem>
 
     class Pojo(var title:String?) {
         init {
@@ -12,4 +13,6 @@ class Vocabulary {
     init {
         pojo = Pojo(null)
     }
+
+
 }

app/src/main/java/com/paktalin/vocabularynotebook/ui/AddWordFragment.kt

@@ -34,9 +34,7 @@ class AddWordFragment : WordFragment() {
     }
 
     override fun updateRecycleView(wordItem: WordItem) {
-        val vocabularyFragment = mainActivity
-                .supportFragmentManager.findFragmentById(R.id.fragment_vocabulary) as VocabularyFragment
-        vocabularyFragment.addWordItem(wordItem)
+        mainActivity.vocabularyFragment.addWordItem(wordItem)
     }
 
     companion object { private val TAG = "VN/" + AddWordFragment::class.java.simpleName }

app/src/main/java/com/paktalin/vocabularynotebook/ui/EditWordFragment.kt

@@ -66,9 +66,7 @@ class EditWordFragment : WordFragment() {
                     Toast.makeText(mainActivity, "Couldn't update the word", Toast.LENGTH_SHORT).show()}    }
 
     override fun updateRecycleView(wordItem: WordItem) {
-        val vocabularyFragment = mainActivity
-                .supportFragmentManager.findFragmentById(R.id.fragment_vocabulary) as VocabularyFragment
-        vocabularyFragment.updateWordItem(wordItem)
+        mainActivity.vocabularyFragment.updateWordItem(wordItem)
     }
 
     companion object { private val TAG = "VN/" + EditWordFragment::class.java.simpleName }

app/src/main/java/com/paktalin/vocabularynotebook/ui/MainActivity.kt

@@ -23,14 +23,13 @@ import kotlinx.android.synthetic.main.fragment_vocabulary.*
 class MainActivity : AppCompatActivity() {
 
     lateinit var vocabularyId: String
-    private lateinit var vocabularyFragment: VocabularyFragment
+    lateinit var vocabularyFragment: VocabularyFragment
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
         hideKeyboard()
         setUpNavigationView()
-        vocabularyFragment = supportFragmentManager.findFragmentById(R.id.fragment_vocabulary) as VocabularyFragment
         extractVocabularyData()
     }
 
@@ -74,7 +73,13 @@ class MainActivity : AppCompatActivity() {
                         val vocabularies: List<DocumentReference> = task.get("vocabularies") as List<DocumentReference>
                         val vocabulary = db.collection("vocabularies").document(vocabularies[0].id)
                         vocabularyId = vocabulary.id
-                        vocabularyFragment.retrieveWordsData(vocabularyId)
+
+                        // start VocabularyFragment
+                        vocabularyFragment = VocabularyFragment()
+                        val arguments = Bundle()
+                        arguments.putString("vocabularyId", vocabularyId)
+                        vocabularyFragment.arguments = arguments
+                        supportFragmentManager.beginTransaction().add(R.id.fragment_container, vocabularyFragment).commitNowAllowingStateLoss()
                     } else { showToastNoWords() }
         }
     }

app/src/main/java/com/paktalin/vocabularynotebook/ui/VocabularyFragment.kt

@@ -3,6 +3,7 @@ package com.paktalin.vocabularynotebook.ui
 import android.os.Bundle
 import android.support.v4.app.Fragment
 import android.support.v7.widget.LinearLayoutManager
+import android.util.Log
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
@@ -27,9 +28,11 @@ class VocabularyFragment : Fragment() {
         return inflater.inflate(R.layout.fragment_vocabulary, container, false)
     }
 
+
     override fun onActivityCreated(savedInstanceState: Bundle?) {
         super.onActivityCreated(savedInstanceState)
         setEmptyAdapter()
+        retrieveWordsData(arguments!!["vocabularyId"] as String)
     }
 
     override fun onDestroy() {
@@ -44,14 +47,17 @@ class VocabularyFragment : Fragment() {
         recyclerView.layoutManager = mLayoutManager
     }
 
-    fun retrieveWordsData(vocabularyId: String) {
+    private fun retrieveWordsData(vocabularyId: String) {
         db.collection(VOCABULARIES).document(vocabularyId).collection(WORDS)
                 .orderBy("time", Query.Direction.DESCENDING)
                 .get()
                 .addOnSuccessListener {
                     if (it.documents.size != 0)
                         setVocabularyAdapter(it.documents, vocabularyId)
-                else (activity as MainActivity).showToastNoWords()}
+                else {
+                        Log.i(TAG, "There are no documents in collection \"words\"")
+                        (activity as MainActivity).showToastNoWords()
+                    }}
     }
 
     private fun setVocabularyAdapter(documents: MutableList<DocumentSnapshot>, vocabularyId: String) {

app/src/main/res/layout/notebook_sheet.xml

@@ -17,6 +17,7 @@
         android:layout_margin="8dp">
 
         <LinearLayout
+            android:id="@+id/fragment_container"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:padding="8dp"
@@ -30,11 +31,6 @@
                 android:layout_height="wrap_content"
                 android:layout_marginTop="8dp" />
 
-            <fragment
-                android:id="@+id/fragment_vocabulary"
-                android:name="com.paktalin.vocabularynotebook.ui.VocabularyFragment"
-                android:layout_width="match_parent"
-                android:layout_height="wrap_content" />
         </LinearLayout>
 
     </ScrollView>