[ADD] all classes and packages according to class diagram

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

@@ -4,7 +4,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    tools:context=".fragments.MainActivity">
+    tools:context=".MainActivity">
 
     <TextView
         android:layout_width="wrap_content"