Added selectionTracker observer

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

@@ -93,9 +93,7 @@ class MainActivity : AppCompatActivity() {
                     if (querySnapshot != null && !querySnapshot.isEmpty) {
                         vocabularyAdapter = VocabularyAdapter(VocabSet.createFromSnapshot(querySnapshot), this@MainActivity)
                         recyclerView.adapter = vocabularyAdapter
-                        setSelectionTracker()
-                        (recyclerView.adapter as VocabularyAdapter).tracker = tracker
-
+                        setUpSelectionTracker()
                     } else showToastNoWords()
                 }
             }
@@ -121,7 +119,7 @@ class MainActivity : AppCompatActivity() {
         shortToast(this, getString(R.string.toast_empty_vocabulary))
     }
 
-    private fun setSelectionTracker() {
+    private fun setUpSelectionTracker() {
         tracker = SelectionTracker.Builder<Long>(
                 "mySelection",
                 recyclerView,
@@ -131,6 +129,18 @@ class MainActivity : AppCompatActivity() {
         ).withSelectionPredicate(
                 SelectionPredicates.createSelectAnything()
         ).build()
+
+        tracker?.addObserver(
+                object : SelectionTracker.SelectionObserver<Long>() {
+                    override fun onSelectionChanged() {
+                        super.onSelectionChanged()
+                        if (tracker?.hasSelection()!!) {
+                            Log.d(TAG, "selection ${tracker?.selection?.toList().toString()}")
+                        }
+                        //TODO my implementation
+                    }
+                })
+        (recyclerView.adapter as VocabularyAdapter).tracker = tracker
     }
 
     override fun onPause() {

app/src/main/res/layout/tag.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"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="@color/colorPrimary"
+    android:orientation="vertical">
+
+    <Spinner
+        android:id="@+id/spinner2"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="8dp"
+        android:layout_marginLeft="8dp"
+        android:layout_marginTop="8dp"
+        android:layout_marginEnd="8dp"
+        android:layout_marginRight="8dp"
+        android:layout_marginBottom="8dp"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+</androidx.constraintlayout.widget.ConstraintLayout>
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