properly handle orientation changes

app/src/main/kotlin/com/simplemobiletools/notes/activities/MainActivity.kt

@@ -6,7 +6,10 @@ import android.support.v4.view.ViewPager
 import android.text.method.ArrowKeyMovementMethod
 import android.text.method.LinkMovementMethod
 import android.util.TypedValue
-import android.view.*
+import android.view.ActionMode
+import android.view.Gravity
+import android.view.Menu
+import android.view.MenuItem
 import com.simplemobiletools.commons.dialogs.FilePickerDialog
 import com.simplemobiletools.commons.dialogs.RadioGroupDialog
 import com.simplemobiletools.commons.extensions.*
@@ -31,7 +34,6 @@ import com.simplemobiletools.notes.helpers.OPEN_NOTE_ID
 import com.simplemobiletools.notes.helpers.TYPE_NOTE
 import com.simplemobiletools.notes.models.Note
 import kotlinx.android.synthetic.main.activity_main.*
-import kotlinx.android.synthetic.main.fragment_note.*
 import java.io.File
 import java.nio.charset.Charset
 
@@ -212,7 +214,11 @@ class MainActivity : SimpleActivity(), ViewPager.OnPageChangeListener {
             hideKeyboard()
     }
 
-    private fun currentNotesView() = if (view_pager == null) null else mAdapter?.getItem(view_pager.currentItem)?.notes_view
+    private fun currentNotesView() = if (view_pager == null) {
+        null
+    } else {
+        mAdapter?.getCurrentNotesView(view_pager.currentItem)
+    }
 
     private fun displayRenameDialog() {
         RenameNoteDialog(this, mDb, mCurrentNote) {
@@ -241,12 +247,9 @@ class MainActivity : SimpleActivity(), ViewPager.OnPageChangeListener {
         invalidateOptionsMenu()
         initViewPager()
         updateSelectedNote(id)
-        view_pager.viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
-            override fun onGlobalLayout() {
-                mAdapter?.focusEditText(getNoteIndexWithId(id))
-                view_pager.viewTreeObserver.removeOnGlobalLayoutListener(this)
-            }
-        })
+        view_pager.onGlobalLayout {
+            mAdapter?.focusEditText(getNoteIndexWithId(id))
+        }
     }
 
     private fun launchAbout() {

app/src/main/kotlin/com/simplemobiletools/notes/adapters/NotesPagerAdapter.kt

@@ -33,6 +33,8 @@ class NotesPagerAdapter(fm: FragmentManager, val notes: List<Note>, val activity
 
     override fun getPageTitle(position: Int) = notes[position].title
 
+    fun getCurrentNotesView(position: Int) = fragments[position]?.getNotesView()
+
     fun getCurrentNoteViewText(position: Int) = fragments[position]?.getCurrentNoteViewText()
 
     fun appendText(position: Int, text: String) = fragments[position]?.getNotesView()?.append(text)
@@ -48,4 +50,9 @@ class NotesPagerAdapter(fm: FragmentManager, val notes: List<Note>, val activity
             activity.showErrorToast(e)
         }
     }
+
+    override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
+        super.destroyItem(container, position, `object`)
+        fragments.removeAt(position)
+    }
 }

app/src/main/kotlin/com/simplemobiletools/notes/fragments/NoteFragment.kt

@@ -32,6 +32,7 @@ class NoteFragment : Fragment() {
         noteId = arguments!!.getInt(NOTE_ID)
         mDb = context!!.dbHelper
         note = mDb.getNote(noteId) ?: return view
+        retainInstance = true
 
         if (context!!.config.clickableLinks) {
             view.notes_view.apply {