diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/CustomEventReminderDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/CustomEventReminderDialog.kt
index f24cbf587..69de4ebec 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/CustomEventReminderDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/CustomEventReminderDialog.kt
@@ -10,7 +10,7 @@ import com.simplemobiletools.commons.extensions.setupDialogStuff
 import com.simplemobiletools.commons.extensions.value
 import kotlinx.android.synthetic.main.dialog_custom_event_reminder.view.*
 
-class CustomEventReminderDialog(val activity: Activity, val selectedMinutes: Int = 0, val callback: (minutes: Int) -> Unit) : AlertDialog.Builder(activity) {
+class CustomEventReminderDialog(val activity: Activity, val selectedMinutes: Int = 0, val callback: (minutes: Int) -> Unit) {
     var dialog: AlertDialog
     var view = (activity.layoutInflater.inflate(R.layout.dialog_custom_event_reminder, null) as ViewGroup).apply {
         if (selectedMinutes == 0) {
@@ -41,7 +41,7 @@ class CustomEventReminderDialog(val activity: Activity, val selectedMinutes: Int
         val value = view.dialog_custom_reminder_value.value
         val multiplier = getMultiplier(view.dialog_radio_view.checkedRadioButtonId)
         val minutes = Integer.valueOf(if (value.isEmpty()) "0" else value)
-        callback.invoke(minutes * multiplier)
+        callback(minutes * multiplier)
         activity.hideKeyboard()
         dialog.dismiss()
     }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/DeleteEventDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/DeleteEventDialog.kt
index ba0640f1f..9654b4885 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/DeleteEventDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/DeleteEventDialog.kt
@@ -9,7 +9,7 @@ import com.simplemobiletools.commons.extensions.beVisibleIf
 import com.simplemobiletools.commons.extensions.setupDialogStuff
 import kotlinx.android.synthetic.main.dialog_delete_event.view.*
 
-class DeleteEventDialog(val activity: Activity, eventIds: List<Int>, val callback: (allOccurrences: Boolean) -> Unit) : AlertDialog.Builder(activity) {
+class DeleteEventDialog(val activity: Activity, eventIds: List<Int>, val callback: (allOccurrences: Boolean) -> Unit) {
     val dialog: AlertDialog?
 
     init {
@@ -36,6 +36,6 @@ class DeleteEventDialog(val activity: Activity, eventIds: List<Int>, val callbac
     private fun dialogConfirmed(view: ViewGroup, hasRepeatableEvent: Boolean) {
         val deleteAllOccurrences = !hasRepeatableEvent || view.delete_event_radio_view.checkedRadioButtonId == R.id.delete_event_all
         dialog?.dismiss()
-        callback.invoke(deleteAllOccurrences)
+        callback(deleteAllOccurrences)
     }
 }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/EditRepeatingEventDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/EditRepeatingEventDialog.kt
index 818e85778..1cd34ff80 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/EditRepeatingEventDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/EditRepeatingEventDialog.kt
@@ -8,7 +8,7 @@ import com.simplemobiletools.calendar.activities.SimpleActivity
 import com.simplemobiletools.commons.extensions.setupDialogStuff
 import kotlinx.android.synthetic.main.dialog_edit_repeating_event.view.*
 
-class EditRepeatingEventDialog(val activity: SimpleActivity, val callback: (allOccurrences: Boolean) -> Unit) : AlertDialog.Builder(activity) {
+class EditRepeatingEventDialog(val activity: SimpleActivity, val callback: (allOccurrences: Boolean) -> Unit) {
     var dialog: AlertDialog
 
     init {
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ExportEventsDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ExportEventsDialog.kt
index 46da7258c..ddfc95c73 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ExportEventsDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ExportEventsDialog.kt
@@ -11,8 +11,7 @@ import com.simplemobiletools.commons.extensions.*
 import kotlinx.android.synthetic.main.dialog_export_events.view.*
 import java.io.File
 
-class ExportEventsDialog(val activity: SimpleActivity, val path: String, val callback: (exportPastEvents: Boolean, file: File, eventTypes: HashSet<String>) -> Unit)
-    : AlertDialog.Builder(activity) {
+class ExportEventsDialog(val activity: SimpleActivity, val path: String, val callback: (exportPastEvents: Boolean, file: File, eventTypes: HashSet<String>) -> Unit) {
 
     init {
         val view = (activity.layoutInflater.inflate(R.layout.dialog_export_events, null) as ViewGroup).apply {
@@ -42,20 +41,20 @@ class ExportEventsDialog(val activity: SimpleActivity, val path: String, val cal
             activity.setupDialogStuff(view, this, R.string.export_events)
             getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener({
                 val filename = view.export_events_filename.value
-                if (filename.isEmpty()) {
-                    activity.toast(R.string.empty_name)
-                } else if (filename.isAValidFilename()) {
-                    val file = File(path, "$filename.ics")
-                    if (file.exists()) {
-                        activity.toast(R.string.name_taken)
-                        return@setOnClickListener
-                    }
+                when {
+                    filename.isEmpty() -> activity.toast(R.string.empty_name)
+                    filename.isAValidFilename() -> {
+                        val file = File(path, "$filename.ics")
+                        if (file.exists()) {
+                            activity.toast(R.string.name_taken)
+                            return@setOnClickListener
+                        }
 
-                    val eventTypes = (view.export_events_types_list.adapter as FilterEventTypeAdapter).getSelectedItemsSet()
-                    callback(view.export_events_checkbox.isChecked, file, eventTypes)
-                    dismiss()
-                } else {
-                    activity.toast(R.string.invalid_name)
+                        val eventTypes = (view.export_events_types_list.adapter as FilterEventTypeAdapter).getSelectedItemsSet()
+                        callback(view.export_events_checkbox.isChecked, file, eventTypes)
+                        dismiss()
+                    }
+                    else -> activity.toast(R.string.invalid_name)
                 }
             })
         }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/FilterEventTypesDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/FilterEventTypesDialog.kt
index 6feb4dc53..fb1b50d59 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/FilterEventTypesDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/FilterEventTypesDialog.kt
@@ -11,7 +11,7 @@ import com.simplemobiletools.commons.extensions.setupDialogStuff
 import kotlinx.android.synthetic.main.dialog_filter_event_types.view.*
 import java.util.*
 
-class FilterEventTypesDialog(val activity: SimpleActivity, val callback: () -> Unit) : AlertDialog.Builder(activity) {
+class FilterEventTypesDialog(val activity: SimpleActivity, val callback: () -> Unit) {
     var dialog: AlertDialog
     var eventTypes = ArrayList<EventType>()
     val view = activity.layoutInflater.inflate(R.layout.dialog_filter_event_types, null)
@@ -35,7 +35,7 @@ class FilterEventTypesDialog(val activity: SimpleActivity, val callback: () -> U
         val selectedItems = (view.filter_event_types_list.adapter as FilterEventTypeAdapter).getSelectedItemsSet()
         if (activity.config.displayEventTypes != selectedItems) {
             activity.config.displayEventTypes = selectedItems
-            callback.invoke()
+            callback()
         }
         dialog.dismiss()
     }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ImportEventsDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ImportEventsDialog.kt
index e14d7b8bf..075b82123 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ImportEventsDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/ImportEventsDialog.kt
@@ -14,7 +14,7 @@ import com.simplemobiletools.commons.extensions.setupDialogStuff
 import com.simplemobiletools.commons.extensions.toast
 import kotlinx.android.synthetic.main.dialog_import_events.view.*
 
-class ImportEventsDialog(val activity: SimpleActivity, val path: String, val callback: (refreshView: Boolean) -> Unit) : AlertDialog.Builder(activity) {
+class ImportEventsDialog(val activity: SimpleActivity, val path: String, val callback: (refreshView: Boolean) -> Unit) {
     var currEventTypeId = DBHelper.REGULAR_EVENT_TYPE_ID
 
     init {
@@ -45,7 +45,7 @@ class ImportEventsDialog(val activity: SimpleActivity, val path: String, val cal
     }
 
     private fun updateEventType(view: ViewGroup) {
-        val eventType = context.dbHelper.getEventType(currEventTypeId)
+        val eventType = activity.dbHelper.getEventType(currEventTypeId)
         view.import_event_type_title.text = eventType!!.getDisplayTitle()
         view.import_event_type_color.setBackgroundWithStroke(eventType.color, activity.config.backgroundColor)
     }
@@ -56,6 +56,6 @@ class ImportEventsDialog(val activity: SimpleActivity, val path: String, val cal
             IMPORT_PARTIAL -> R.string.importing_some_events_failed
             else -> R.string.importing_events_failed
         })
-        callback.invoke(result != IMPORT_FAIL)
+        callback(result != IMPORT_FAIL)
     }
 }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatLimitTypePickerDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatLimitTypePickerDialog.kt
index 6c577ecbf..29b5988de 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatLimitTypePickerDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatLimitTypePickerDialog.kt
@@ -17,8 +17,7 @@ import kotlinx.android.synthetic.main.dialog_repeat_limit_type_picker.view.*
 import org.joda.time.DateTime
 import java.util.*
 
-class RepeatLimitTypePickerDialog(val activity: Activity, var repeatLimit: Int, val startTS: Int, val callback: (repeatLimit: Int) -> Unit) :
-        AlertDialog.Builder(activity) {
+class RepeatLimitTypePickerDialog(val activity: Activity, var repeatLimit: Int, val startTS: Int, val callback: (repeatLimit: Int) -> Unit) {
     lateinit var dialog: AlertDialog
     var view: View
 
@@ -45,14 +44,13 @@ class RepeatLimitTypePickerDialog(val activity: Activity, var repeatLimit: Int,
         }
     }
 
-    private fun getCheckedItem(): Int {
-        return if (repeatLimit > 0)
-            R.id.repeat_type_till_date
-        else if (repeatLimit < 0) {
+    private fun getCheckedItem() = when {
+        repeatLimit > 0 -> R.id.repeat_type_till_date
+        repeatLimit < 0 -> {
             view.repeat_type_count.setText((-repeatLimit).toString())
             R.id.repeat_type_x_times
-        } else
-            R.id.repeat_type_forever
+        }
+        else -> R.id.repeat_type_forever
     }
 
     private fun updateRepeatLimitText() {
@@ -95,10 +93,10 @@ class RepeatLimitTypePickerDialog(val activity: Activity, var repeatLimit: Int,
 
     private val repetitionLimitDateSetListener = DatePickerDialog.OnDateSetListener { v, year, monthOfYear, dayOfMonth ->
         val repeatLimitDateTime = DateTime().withDate(year, monthOfYear + 1, dayOfMonth).withTime(23, 59, 59, 0)
-        if (repeatLimitDateTime.seconds() < startTS) {
-            repeatLimit = 0
+        repeatLimit = if (repeatLimitDateTime.seconds() < startTS) {
+            0
         } else {
-            repeatLimit = repeatLimitDateTime.seconds()
+            repeatLimitDateTime.seconds()
         }
         callback(repeatLimit)
         dialog.dismiss()
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatRuleWeeklyDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatRuleWeeklyDialog.kt
index d69ce0ddb..18e694065 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatRuleWeeklyDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/RepeatRuleWeeklyDialog.kt
@@ -8,8 +8,7 @@ import com.simplemobiletools.commons.extensions.setupDialogStuff
 import com.simplemobiletools.commons.views.MyAppCompatCheckbox
 import kotlinx.android.synthetic.main.dialog_vertical_linear_layout.view.*
 
-class RepeatRuleWeeklyDialog(val activity: Activity, val curRepeatRule: Int, val callback: (repeatRule: Int) -> Unit) :
-        AlertDialog.Builder(activity) {
+class RepeatRuleWeeklyDialog(val activity: Activity, val curRepeatRule: Int, val callback: (repeatRule: Int) -> Unit) {
     val dialog: AlertDialog
     val view = activity.layoutInflater.inflate(R.layout.dialog_vertical_linear_layout, null)
 
@@ -46,7 +45,7 @@ class RepeatRuleWeeklyDialog(val activity: Activity, val curRepeatRule: Int, val
     private fun getRepeatRuleSum(): Int {
         var sum = 0
         val cnt = view.dialog_vertical_linear_layout.childCount
-        for (i in 0..cnt - 1) {
+        for (i in 0 until cnt) {
             val child = view.dialog_vertical_linear_layout.getChildAt(i)
             if (child is MyAppCompatCheckbox) {
                 if (child.isChecked)
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectCalendarsDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectCalendarsDialog.kt
index 509cb4284..cf0fda542 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectCalendarsDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectCalendarsDialog.kt
@@ -14,7 +14,7 @@ import kotlinx.android.synthetic.main.calendar_item_account.view.*
 import kotlinx.android.synthetic.main.calendar_item_calendar.view.*
 import kotlinx.android.synthetic.main.dialog_select_calendars.view.*
 
-class SelectCalendarsDialog(val activity: Activity, val callback: () -> Unit) : AlertDialog.Builder(activity) {
+class SelectCalendarsDialog(val activity: Activity, val callback: () -> Unit) {
     var prevAccount = ""
     var dialog: AlertDialog
     var view = (activity.layoutInflater.inflate(R.layout.dialog_select_calendars, null) as ViewGroup)
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventCalendarDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventCalendarDialog.kt
index 0b6a5a954..0ae96e8d6 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventCalendarDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventCalendarDialog.kt
@@ -63,7 +63,7 @@ class SelectEventCalendarDialog(val activity: Activity, val calendars: List<CalD
         if (!wasInit)
             return
 
-        callback.invoke(typeId)
+        callback(typeId)
         dialog?.dismiss()
     }
 }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeColorDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeColorDialog.kt
index 2af69d1a7..b59387982 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeColorDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeColorDialog.kt
@@ -55,7 +55,7 @@ class SelectEventTypeColorDialog(val activity: Activity, val eventType: EventTyp
         if (!wasInit)
             return
 
-        callback.invoke(colors[colorKey])
+        callback(colors[colorKey])
         dialog?.dismiss()
     }
 }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeDialog.kt
index 466fe510f..2831ee682 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SelectEventTypeDialog.kt
@@ -69,12 +69,12 @@ class SelectEventTypeDialog(val activity: Activity, val currEventType: Int, val
 
         if (typeId == NEW_TYPE_ID) {
             UpdateEventTypeDialog(activity) {
-                callback.invoke(it)
+                callback(it)
                 activity.hideKeyboard()
                 dialog?.dismiss()
             }
         } else {
-            callback.invoke(typeId)
+            callback(typeId)
             dialog?.dismiss()
         }
     }
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SnoozePickerDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SnoozePickerDialog.kt
index a7695f902..0a655d0aa 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SnoozePickerDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/SnoozePickerDialog.kt
@@ -9,8 +9,7 @@ import com.simplemobiletools.commons.extensions.setupDialogStuff
 import com.simplemobiletools.commons.extensions.value
 import kotlinx.android.synthetic.main.dialog_snooze_picker.view.*
 
-class SnoozePickerDialog(val activity: SimpleActivity, val minutes: Int, val callback: (newMinutes: Int) -> Unit)
-    : AlertDialog.Builder(activity) {
+class SnoozePickerDialog(val activity: SimpleActivity, val minutes: Int, val callback: (newMinutes: Int) -> Unit) {
     init {
         val view = (activity.layoutInflater.inflate(R.layout.dialog_snooze_picker, null) as ViewGroup).apply {
             snooze_picker_label.text = snooze_picker_label.text.toString().capitalize()
diff --git a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/UpdateEventTypeDialog.kt b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/UpdateEventTypeDialog.kt
index 055e54d47..641035672 100644
--- a/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/UpdateEventTypeDialog.kt
+++ b/app/src/main/kotlin/com/simplemobiletools/calendar/dialogs/UpdateEventTypeDialog.kt
@@ -15,7 +15,7 @@ import com.simplemobiletools.commons.extensions.toast
 import com.simplemobiletools.commons.extensions.value
 import kotlinx.android.synthetic.main.dialog_event_type.view.*
 
-class UpdateEventTypeDialog(val activity: Activity, var eventType: EventType? = null, val callback: (eventTypeId: Int) -> Unit) : AlertDialog.Builder(activity) {
+class UpdateEventTypeDialog(val activity: Activity, var eventType: EventType? = null, val callback: (eventTypeId: Int) -> Unit) {
     var isNewEvent = eventType == null
 
     init {
@@ -73,7 +73,7 @@ class UpdateEventTypeDialog(val activity: Activity, var eventType: EventType? =
 
                 if (eventTypeId != -1) {
                     dismiss()
-                    callback.invoke(eventTypeId)
+                    callback(eventTypeId)
                 } else {
                     activity.toast(R.string.editing_calendar_failed)
                 }