convert DBHelper to kotlin

app/src/main/java/com/simplemobiletools/calendar/CalendarImpl.java

@@ -30,7 +30,7 @@ public class CalendarImpl implements DBHelper.DBOperationsListener {
         mTargetDate = targetDate;
         final int startTS = Formatter.getDayStartTS(Formatter.getDayCodeFromDateTime(mTargetDate.minusMonths(1)));
         final int endTS = Formatter.getDayEndTS(Formatter.getDayCodeFromDateTime(mTargetDate.plusMonths(1)));
-        DBHelper.newInstance(mContext, this).getEvents(startTS, endTS);
+        DBHelper.Companion.newInstance(mContext, this).getEvents(startTS, endTS);
     }
 
     public void getPrevMonth() {

app/src/main/java/com/simplemobiletools/calendar/DBHelper.java

@@ -1,297 +0,0 @@
-package com.simplemobiletools.calendar;
-
-import android.content.ContentValues;
-import android.content.Context;
-import android.database.Cursor;
-import android.database.sqlite.SQLiteDatabase;
-import android.database.sqlite.SQLiteOpenHelper;
-import android.database.sqlite.SQLiteQueryBuilder;
-import android.text.TextUtils;
-
-import com.simplemobiletools.calendar.models.Event;
-
-import org.joda.time.DateTime;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public class DBHelper extends SQLiteOpenHelper {
-    private static SQLiteDatabase mDb;
-    private static DBOperationsListener mCallback;
-
-    private static final String DB_NAME = "events.db";
-    private static final int DB_VERSION = 3;
-
-    private static final String MAIN_TABLE_NAME = "events";
-    private static final String COL_ID = "id";
-    private static final String COL_START_TS = "start_ts";
-    private static final String COL_END_TS = "end_ts";
-    private static final String COL_TITLE = "title";
-    private static final String COL_DESCRIPTION = "description";
-    private static final String COL_REMINDER_MINUTES = "reminder_minutes";
-
-    private static final String META_TABLE_NAME = "events_meta";
-    private static final String COL_EVENT_ID = "event_id";
-    private static final String COL_REPEAT_START = "repeat_start";
-    private static final String COL_REPEAT_INTERVAL = "repeat_interval";
-    private static final String COL_REPEAT_MONTH = "repeat_month";
-    private static final String COL_REPEAT_DAY = "repeat_day";
-
-    public static DBHelper newInstance(Context context, DBOperationsListener callback) {
-        mCallback = callback;
-        return new DBHelper(context);
-    }
-
-    public DBHelper(Context context) {
-        super(context, DB_NAME, null, DB_VERSION);
-        mDb = getWritableDatabase();
-    }
-
-    @Override
-    public void onCreate(SQLiteDatabase db) {
-        db.execSQL("CREATE TABLE " + MAIN_TABLE_NAME + " (" +
-                COL_ID + " INTEGER PRIMARY KEY, " +
-                COL_START_TS + " INTEGER," +
-                COL_END_TS + " INTEGER," +
-                COL_TITLE + " TEXT," +
-                COL_DESCRIPTION + " TEXT," +
-                COL_REMINDER_MINUTES + " INTEGER" +
-                ")");
-
-        createMetaTable(db);
-    }
-
-    @Override
-    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-        if (oldVersion == 1) {
-            db.execSQL("ALTER TABLE " + MAIN_TABLE_NAME + " ADD COLUMN " + COL_REMINDER_MINUTES + " INTEGER DEFAULT -1");
-        }
-
-        if (newVersion == 3) {
-            createMetaTable(db);
-        }
-    }
-
-    private void createMetaTable(SQLiteDatabase db) {
-        db.execSQL("CREATE TABLE " + META_TABLE_NAME + " (" +
-                COL_ID + " INTEGER PRIMARY KEY, " +
-                COL_EVENT_ID + " INTEGER UNIQUE, " +
-                COL_REPEAT_START + " INTEGER, " +
-                COL_REPEAT_INTERVAL + " INTEGER, " +
-                COL_REPEAT_MONTH + " INTEGER, " +
-                COL_REPEAT_DAY + " INTEGER" +
-                ")");
-    }
-
-    public void insert(Event event) {
-        final ContentValues eventValues = fillContentValues(event);
-        long id = mDb.insert(MAIN_TABLE_NAME, null, eventValues);
-        event.setId((int) id);
-        if (event.getRepeatInterval() != 0) {
-            final ContentValues metaValues = fillMetaValues(event);
-            mDb.insert(META_TABLE_NAME, null, metaValues);
-        }
-
-        if (mCallback != null)
-            mCallback.eventInserted(event);
-    }
-
-    public void update(Event event) {
-        final String[] selectionArgs = {String.valueOf(event.getId())};
-        final ContentValues values = fillContentValues(event);
-        final String selection = COL_ID + " = ?";
-        mDb.update(MAIN_TABLE_NAME, values, selection, selectionArgs);
-
-        if (event.getRepeatInterval() == 0) {
-            final String metaSelection = COL_EVENT_ID + " = ?";
-            mDb.delete(META_TABLE_NAME, metaSelection, selectionArgs);
-        } else {
-            final ContentValues metaValues = fillMetaValues(event);
-            mDb.insertWithOnConflict(META_TABLE_NAME, null, metaValues, SQLiteDatabase.CONFLICT_REPLACE);
-        }
-
-        if (mCallback != null)
-            mCallback.eventUpdated(event);
-    }
-
-    private ContentValues fillContentValues(Event event) {
-        final ContentValues values = new ContentValues();
-        values.put(COL_START_TS, event.getStartTS());
-        values.put(COL_END_TS, event.getEndTS());
-        values.put(COL_TITLE, event.getTitle());
-        values.put(COL_DESCRIPTION, event.getDescription());
-        values.put(COL_REMINDER_MINUTES, event.getReminderMinutes());
-        return values;
-    }
-
-    private ContentValues fillMetaValues(Event event) {
-        final int repeatInterval = event.getRepeatInterval();
-        final ContentValues values = new ContentValues();
-        values.put(COL_EVENT_ID, event.getId());
-        values.put(COL_REPEAT_START, event.getStartTS());
-        values.put(COL_REPEAT_INTERVAL, repeatInterval);
-        final DateTime dateTime = Formatter.getDateTimeFromTS(event.getStartTS());
-
-        if (repeatInterval == Constants.MONTH || repeatInterval == Constants.YEAR) {
-            values.put(COL_REPEAT_DAY, dateTime.getDayOfMonth());
-        }
-
-        if (repeatInterval == Constants.YEAR) {
-            values.put(COL_REPEAT_MONTH, dateTime.getMonthOfYear());
-        }
-
-        return values;
-    }
-
-    public void deleteEvents(String[] ids) {
-        final String args = TextUtils.join(", ", ids);
-        final String selection = COL_ID + " IN (" + args + ")";
-        mDb.delete(MAIN_TABLE_NAME, selection, null);
-
-        final String metaSelection = COL_EVENT_ID + " IN (" + args + ")";
-        mDb.delete(META_TABLE_NAME, metaSelection, null);
-
-        if (mCallback != null)
-            mCallback.eventsDeleted(ids.length);
-    }
-
-    public Event getEvent(int id) {
-        final String selection = MAIN_TABLE_NAME + "." + COL_ID + " = ?";
-        final String[] selectionArgs = {String.valueOf(id)};
-        final Cursor cursor = getEventsCursor(selection, selectionArgs);
-        final List<Event> events = fillEvents(cursor);
-        if (!events.isEmpty())
-            return events.get(0);
-
-        return null;
-    }
-
-    public void getEvents(int fromTS, int toTS) {
-        final List<Event> events = new ArrayList<>();
-        for (int ts = fromTS; ts <= toTS; ts += Constants.DAY) {
-            events.addAll(getEventsFor(ts));
-        }
-
-        final String selection = COL_START_TS + " <= ? AND " + COL_END_TS + " >= ? AND " + COL_REPEAT_INTERVAL + " IS NULL";
-        final String[] selectionArgs = {String.valueOf(toTS), String.valueOf(fromTS)};
-        final Cursor cursor = getEventsCursor(selection, selectionArgs);
-        if (cursor != null) {
-            events.addAll(fillEvents(cursor));
-        }
-
-        if (mCallback != null)
-            mCallback.gotEvents(events);
-    }
-
-    private List<Event> getEventsFor(int ts) {
-        final List<Event> newEvents = new ArrayList<>();
-        final int dayExclusive = Constants.DAY - 1;
-        final int dayEnd = ts + dayExclusive;
-        final DateTime dateTime = Formatter.getDateTimeFromTS(ts);
-
-        // get daily and weekly events
-        String selection = "(" + COL_REPEAT_INTERVAL + " = " + Constants.DAY + " OR " + COL_REPEAT_INTERVAL + " = " + Constants.WEEK +
-                ") AND (" + dayEnd + " - " + COL_REPEAT_START + ") % " + COL_REPEAT_INTERVAL + " BETWEEN 0 AND " + dayExclusive;
-        newEvents.addAll(getEvents(selection, ts));
-
-        // get monthly events
-        selection = COL_REPEAT_INTERVAL + " = " + Constants.MONTH + " AND " + COL_REPEAT_DAY + " = " + dateTime.getDayOfMonth() +
-                " AND " + COL_REPEAT_START + " <= " + dayEnd;
-        newEvents.addAll(getEvents(selection, ts));
-
-        // get yearly events
-        selection = COL_REPEAT_INTERVAL + " = " + Constants.YEAR + " AND " + COL_REPEAT_MONTH + " = " + dateTime.getMonthOfYear() +
-                " AND " + COL_REPEAT_DAY + " = " + dateTime.getDayOfMonth() + " AND " + COL_REPEAT_START + " <= " + dayEnd;
-        newEvents.addAll(getEvents(selection, ts));
-
-        return newEvents;
-    }
-
-    private List<Event> getEvents(String selection, int ts) {
-        final List<Event> events = new ArrayList<>();
-        final Cursor cursor = getEventsCursor(selection, null);
-        if (cursor != null) {
-            final List<Event> currEvents = fillEvents(cursor);
-            for (Event e : currEvents) {
-                updateEventTimes(e, ts);
-            }
-            events.addAll(currEvents);
-        }
-
-        return events;
-    }
-
-    private void updateEventTimes(Event e, int ts) {
-        final int periods = (ts - e.getStartTS() + Constants.DAY) / e.getRepeatInterval();
-        DateTime currStart = Formatter.getDateTimeFromTS(e.getStartTS());
-        DateTime newStart;
-        if (e.getRepeatInterval() == Constants.DAY) {
-            newStart = currStart.plusDays(periods);
-        } else if (e.getRepeatInterval() == Constants.WEEK) {
-            newStart = currStart.plusWeeks(periods);
-        } else if (e.getRepeatInterval() == Constants.MONTH) {
-            newStart = currStart.plusMonths(periods);
-        } else {
-            newStart = currStart.plusYears(periods);
-        }
-
-        final int newStartTS = (int) (newStart.getMillis() / 1000);
-        final int newEndTS = newStartTS + (e.getEndTS() - e.getStartTS());
-        e.setStartTS(newStartTS);
-        e.setEndTS(newEndTS);
-    }
-
-    public List<Event> getEventsAtReboot() {
-        List<Event> events = new ArrayList<>();
-        final String selection = COL_REMINDER_MINUTES + " != -1 AND (" + COL_START_TS + " > ? OR " + COL_REPEAT_INTERVAL + " != 0)";
-        final String[] selectionArgs = {String.valueOf(DateTime.now().getMillis() / 1000)};
-        final Cursor cursor = getEventsCursor(selection, selectionArgs);
-
-        if (cursor != null) {
-            events = fillEvents(cursor);
-        }
-
-        return events;
-    }
-
-    private Cursor getEventsCursor(String selection, String[] selectionArgs) {
-        final SQLiteQueryBuilder builder = new SQLiteQueryBuilder();
-        builder.setTables(
-                MAIN_TABLE_NAME + " LEFT OUTER JOIN " + META_TABLE_NAME + " ON " + COL_EVENT_ID + " = " + MAIN_TABLE_NAME + "." + COL_ID);
-        final String[] projection = getAllColumns();
-        return builder.query(mDb, projection, selection, selectionArgs, MAIN_TABLE_NAME + "." + COL_ID, null, COL_START_TS);
-    }
-
-    private String[] getAllColumns() {
-        return new String[]{MAIN_TABLE_NAME + "." + COL_ID, COL_START_TS, COL_END_TS, COL_TITLE, COL_DESCRIPTION, COL_REMINDER_MINUTES,
-                COL_REPEAT_INTERVAL, COL_REPEAT_MONTH, COL_REPEAT_DAY};
-    }
-
-    private List<Event> fillEvents(Cursor cursor) {
-        final List<Event> events = new ArrayList<>();
-        if (cursor.moveToFirst()) {
-            do {
-                final int id = cursor.getInt(cursor.getColumnIndex(COL_ID));
-                final int startTS = cursor.getInt(cursor.getColumnIndex(COL_START_TS));
-                final int endTS = cursor.getInt(cursor.getColumnIndex(COL_END_TS));
-                final int reminderMinutes = cursor.getInt(cursor.getColumnIndex(COL_REMINDER_MINUTES));
-                final int repeatInterval = cursor.getInt(cursor.getColumnIndex(COL_REPEAT_INTERVAL));
-                final String title = cursor.getString(cursor.getColumnIndex(COL_TITLE));
-                final String description = cursor.getString(cursor.getColumnIndex(COL_DESCRIPTION));
-                events.add(new Event(id, startTS, endTS, title, description, reminderMinutes, repeatInterval));
-            } while (cursor.moveToNext());
-        }
-        cursor.close();
-        return events;
-    }
-
-    public interface DBOperationsListener {
-        void eventInserted(Event event);
-
-        void eventUpdated(Event event);
-
-        void eventsDeleted(int cnt);
-
-        void gotEvents(List<Event> events);
-    }
-}

app/src/main/java/com/simplemobiletools/calendar/activities/EventActivity.java

@@ -226,7 +226,7 @@ public class EventActivity extends SimpleActivity implements DBHelper.DBOperatio
             return;
         }
 
-        final DBHelper dbHelper = DBHelper.newInstance(getApplicationContext(), this);
+        final DBHelper dbHelper = DBHelper.Companion.newInstance(getApplicationContext(), this);
         final String description = mDescriptionET.getText().toString().trim();
         mEvent.setStartTS(startTS);
         mEvent.setEndTS(mEndCheckbox.isChecked() ? endTS : startTS);

app/src/main/java/com/simplemobiletools/calendar/receivers/BootCompletedReceiver.java

@@ -14,7 +14,7 @@ public class BootCompletedReceiver extends BroadcastReceiver {
 
     @Override
     public void onReceive(Context context, Intent arg1) {
-        final List<Event> events = DBHelper.newInstance(context, null).getEventsAtReboot();
+        final List<Event> events = DBHelper.Companion.newInstance(context, null).getEventsAtReboot();
         for (Event event : events) {
             Utils.scheduleNextEvent(context, event);
         }

app/src/main/java/com/simplemobiletools/calendar/receivers/NotificationReceiver.java

@@ -26,7 +26,7 @@ public class NotificationReceiver extends BroadcastReceiver {
         if (id == -1)
             return;
 
-        final Event event = DBHelper.newInstance(context, null).getEvent(id);
+        final Event event = DBHelper.Companion.newInstance(context, null).getEvent(id);
         if (event == null || event.getReminderMinutes() == -1)
             return;
 

app/src/main/kotlin/com/simplemobiletools/calendar/DBHelper.kt

@@ -0,0 +1,287 @@
+package com.simplemobiletools.calendar
+
+import android.content.ContentValues
+import android.content.Context
+import android.database.Cursor
+import android.database.sqlite.SQLiteDatabase
+import android.database.sqlite.SQLiteOpenHelper
+import android.database.sqlite.SQLiteQueryBuilder
+import android.text.TextUtils
+import com.simplemobiletools.calendar.models.Event
+import org.joda.time.DateTime
+import java.util.*
+
+class DBHelper(context: Context) : SQLiteOpenHelper(context, DBHelper.DB_NAME, null, DBHelper.DB_VERSION) {
+
+    init {
+        mDb = writableDatabase
+    }
+
+    override fun onCreate(db: SQLiteDatabase) {
+        db.execSQL("CREATE TABLE " + MAIN_TABLE_NAME + " (" +
+                COL_ID + " INTEGER PRIMARY KEY, " +
+                COL_START_TS + " INTEGER," +
+                COL_END_TS + " INTEGER," +
+                COL_TITLE + " TEXT," +
+                COL_DESCRIPTION + " TEXT," +
+                COL_REMINDER_MINUTES + " INTEGER" +
+                ")")
+
+        createMetaTable(db)
+    }
+
+    override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
+        if (oldVersion == 1) {
+            db.execSQL("ALTER TABLE $MAIN_TABLE_NAME ADD COLUMN $COL_REMINDER_MINUTES INTEGER DEFAULT -1")
+        }
+
+        if (newVersion == 3) {
+            createMetaTable(db)
+        }
+    }
+
+    private fun createMetaTable(db: SQLiteDatabase) {
+        db.execSQL("CREATE TABLE " + META_TABLE_NAME + " (" +
+                COL_ID + " INTEGER PRIMARY KEY, " +
+                COL_EVENT_ID + " INTEGER UNIQUE, " +
+                COL_REPEAT_START + " INTEGER, " +
+                COL_REPEAT_INTERVAL + " INTEGER, " +
+                COL_REPEAT_MONTH + " INTEGER, " +
+                COL_REPEAT_DAY + " INTEGER" +
+                ")")
+    }
+
+    fun insert(event: Event) {
+        val eventValues = fillContentValues(event)
+        val id = mDb.insert(MAIN_TABLE_NAME, null, eventValues)
+        event.id = id.toInt()
+        if (event.repeatInterval != 0) {
+            val metaValues = fillMetaValues(event)
+            mDb.insert(META_TABLE_NAME, null, metaValues)
+        }
+
+        if (mCallback != null)
+            mCallback!!.eventInserted(event)
+    }
+
+    fun update(event: Event) {
+        val selectionArgs = arrayOf(event.id.toString())
+        val values = fillContentValues(event)
+        val selection = COL_ID + " = ?"
+        mDb.update(MAIN_TABLE_NAME, values, selection, selectionArgs)
+
+        if (event.repeatInterval == 0) {
+            val metaSelection = COL_EVENT_ID + " = ?"
+            mDb.delete(META_TABLE_NAME, metaSelection, selectionArgs)
+        } else {
+            val metaValues = fillMetaValues(event)
+            mDb.insertWithOnConflict(META_TABLE_NAME, null, metaValues, SQLiteDatabase.CONFLICT_REPLACE)
+        }
+
+        if (mCallback != null)
+            mCallback!!.eventUpdated(event)
+    }
+
+    private fun fillContentValues(event: Event): ContentValues {
+        val values = ContentValues()
+        values.put(COL_START_TS, event.startTS)
+        values.put(COL_END_TS, event.endTS)
+        values.put(COL_TITLE, event.title)
+        values.put(COL_DESCRIPTION, event.description)
+        values.put(COL_REMINDER_MINUTES, event.reminderMinutes)
+        return values
+    }
+
+    private fun fillMetaValues(event: Event): ContentValues {
+        val repeatInterval = event.repeatInterval
+        val values = ContentValues()
+        values.put(COL_EVENT_ID, event.id)
+        values.put(COL_REPEAT_START, event.startTS)
+        values.put(COL_REPEAT_INTERVAL, repeatInterval)
+        val dateTime = Formatter.getDateTimeFromTS(event.startTS)
+
+        if (repeatInterval == Constants.MONTH || repeatInterval == Constants.YEAR) {
+            values.put(COL_REPEAT_DAY, dateTime.dayOfMonth)
+        }
+
+        if (repeatInterval == Constants.YEAR) {
+            values.put(COL_REPEAT_MONTH, dateTime.monthOfYear)
+        }
+
+        return values
+    }
+
+    fun deleteEvents(ids: Array<String>) {
+        val args = TextUtils.join(", ", ids)
+        val selection = "$COL_ID IN ($args)"
+        mDb.delete(MAIN_TABLE_NAME, selection, null)
+
+        val metaSelection = "$COL_EVENT_ID IN ($args)"
+        mDb.delete(META_TABLE_NAME, metaSelection, null)
+
+        if (mCallback != null)
+            mCallback!!.eventsDeleted(ids.size)
+    }
+
+    fun getEvent(id: Int): Event? {
+        val selection = "$MAIN_TABLE_NAME.$COL_ID = ?"
+        val selectionArgs = arrayOf(id.toString())
+        val cursor = getEventsCursor(selection, selectionArgs)
+        val events = fillEvents(cursor)
+        if (!events.isEmpty())
+            return events[0]
+
+        return null
+    }
+
+    fun getEvents(fromTS: Int, toTS: Int) {
+        val events = ArrayList<Event>()
+        var ts = fromTS
+        while (ts <= toTS) {
+            events.addAll(getEventsFor(ts))
+            ts += Constants.DAY
+        }
+
+        val selection = "$COL_START_TS <= ? AND $COL_END_TS >= ? AND $COL_REPEAT_INTERVAL IS NULL"
+        val selectionArgs = arrayOf(toTS.toString(), fromTS.toString())
+        val cursor = getEventsCursor(selection, selectionArgs)
+        events.addAll(fillEvents(cursor))
+
+        if (mCallback != null)
+            mCallback!!.gotEvents(events)
+    }
+
+    private fun getEventsFor(ts: Int): List<Event> {
+        val newEvents = ArrayList<Event>()
+        val dayExclusive = Constants.DAY - 1
+        val dayEnd = ts + dayExclusive
+        val dateTime = Formatter.getDateTimeFromTS(ts)
+
+        // get daily and weekly events
+        var selection = "(" + COL_REPEAT_INTERVAL + " = " + Constants.DAY + " OR " + COL_REPEAT_INTERVAL + " = " + Constants.WEEK +
+                ") AND (" + dayEnd + " - " + COL_REPEAT_START + ") % " + COL_REPEAT_INTERVAL + " BETWEEN 0 AND " + dayExclusive
+        newEvents.addAll(getEvents(selection, ts))
+
+        // get monthly events
+        selection = COL_REPEAT_INTERVAL + " = " + Constants.MONTH + " AND " + COL_REPEAT_DAY + " = " + dateTime.dayOfMonth +
+                " AND " + COL_REPEAT_START + " <= " + dayEnd
+        newEvents.addAll(getEvents(selection, ts))
+
+        // get yearly events
+        selection = COL_REPEAT_INTERVAL + " = " + Constants.YEAR + " AND " + COL_REPEAT_MONTH + " = " + dateTime.monthOfYear +
+                " AND " + COL_REPEAT_DAY + " = " + dateTime.dayOfMonth + " AND " + COL_REPEAT_START + " <= " + dayEnd
+        newEvents.addAll(getEvents(selection, ts))
+
+        return newEvents
+    }
+
+    private fun getEvents(selection: String, ts: Int): List<Event> {
+        val events = ArrayList<Event>()
+        val cursor = getEventsCursor(selection, null)
+        if (cursor != null) {
+            val currEvents = fillEvents(cursor)
+            for (e in currEvents) {
+                updateEventTimes(e, ts)
+            }
+            events.addAll(currEvents)
+        }
+
+        return events
+    }
+
+    private fun updateEventTimes(e: Event, ts: Int) {
+        val periods = (ts - e.startTS + Constants.DAY) / e.repeatInterval
+        val currStart = Formatter.getDateTimeFromTS(e.startTS)
+        val newStart: DateTime
+        if (e.repeatInterval == Constants.DAY) {
+            newStart = currStart.plusDays(periods)
+        } else if (e.repeatInterval == Constants.WEEK) {
+            newStart = currStart.plusWeeks(periods)
+        } else if (e.repeatInterval == Constants.MONTH) {
+            newStart = currStart.plusMonths(periods)
+        } else {
+            newStart = currStart.plusYears(periods)
+        }
+
+        val newStartTS = (newStart.millis / 1000).toInt()
+        val newEndTS = newStartTS + (e.endTS - e.startTS)
+        e.startTS = newStartTS
+        e.endTS = newEndTS
+    }
+
+    fun getEventsAtReboot(): List<Event> {
+        val selection = "$COL_REMINDER_MINUTES != -1 AND ($COL_START_TS > ? OR $COL_REPEAT_INTERVAL != 0)"
+        val selectionArgs = arrayOf((DateTime.now().millis / 1000).toString())
+        val cursor = getEventsCursor(selection, selectionArgs)
+        return fillEvents(cursor)
+    }
+
+    private fun getEventsCursor(selection: String, selectionArgs: Array<String>?): Cursor? {
+        val builder = SQLiteQueryBuilder()
+        builder.tables = "$MAIN_TABLE_NAME LEFT OUTER JOIN $META_TABLE_NAME ON $COL_EVENT_ID = $MAIN_TABLE_NAME.$COL_ID"
+        val projection = allColumns
+        return builder.query(mDb, projection, selection, selectionArgs, MAIN_TABLE_NAME + "." + COL_ID, null, COL_START_TS)
+    }
+
+    private val allColumns: Array<String>
+        get() = arrayOf(MAIN_TABLE_NAME + "." + COL_ID, COL_START_TS, COL_END_TS, COL_TITLE, COL_DESCRIPTION, COL_REMINDER_MINUTES, COL_REPEAT_INTERVAL, COL_REPEAT_MONTH, COL_REPEAT_DAY)
+
+    private fun fillEvents(cursor: Cursor?): List<Event> {
+        val events = ArrayList<Event>()
+        if (cursor == null)
+            return events
+
+        if (cursor.moveToFirst()) {
+            do {
+                val id = cursor.getInt(cursor.getColumnIndex(COL_ID))
+                val startTS = cursor.getInt(cursor.getColumnIndex(COL_START_TS))
+                val endTS = cursor.getInt(cursor.getColumnIndex(COL_END_TS))
+                val reminderMinutes = cursor.getInt(cursor.getColumnIndex(COL_REMINDER_MINUTES))
+                val repeatInterval = cursor.getInt(cursor.getColumnIndex(COL_REPEAT_INTERVAL))
+                val title = cursor.getString(cursor.getColumnIndex(COL_TITLE))
+                val description = cursor.getString(cursor.getColumnIndex(COL_DESCRIPTION))
+                events.add(Event(id, startTS, endTS, title, description, reminderMinutes, repeatInterval))
+            } while (cursor.moveToNext())
+        }
+        cursor.close()
+        return events
+    }
+
+    interface DBOperationsListener {
+        fun eventInserted(event: Event)
+
+        fun eventUpdated(event: Event)
+
+        fun eventsDeleted(cnt: Int)
+
+        fun gotEvents(events: MutableList<Event>)
+    }
+
+    companion object {
+        lateinit private var mDb: SQLiteDatabase
+        private var mCallback: DBOperationsListener? = null
+
+        private val DB_NAME = "events.db"
+        private val DB_VERSION = 3
+
+        private val MAIN_TABLE_NAME = "events"
+        private val COL_ID = "id"
+        private val COL_START_TS = "start_ts"
+        private val COL_END_TS = "end_ts"
+        private val COL_TITLE = "title"
+        private val COL_DESCRIPTION = "description"
+        private val COL_REMINDER_MINUTES = "reminder_minutes"
+
+        private val META_TABLE_NAME = "events_meta"
+        private val COL_EVENT_ID = "event_id"
+        private val COL_REPEAT_START = "repeat_start"
+        private val COL_REPEAT_INTERVAL = "repeat_interval"
+        private val COL_REPEAT_MONTH = "repeat_month"
+        private val COL_REPEAT_DAY = "repeat_day"
+
+        fun newInstance(context: Context, callback: DBOperationsListener): DBHelper {
+            mCallback = callback
+            return DBHelper(context)
+        }
+    }
+}

app/src/main/kotlin/com/simplemobiletools/calendar/fragments/DayFragment.kt

@@ -23,6 +23,7 @@ import kotlinx.android.synthetic.main.top_navigation.view.*
 import java.util.*
 
 class DayFragment : Fragment(), DBHelper.DBOperationsListener, AdapterView.OnItemClickListener, AbsListView.MultiChoiceModeListener {
+
     private val EDIT_EVENT = 1
 
     private var mTextColor: Int = 0
@@ -171,7 +172,7 @@ class DayFragment : Fragment(), DBHelper.DBOperationsListener, AdapterView.OnIte
 
     fun deleteEvents() {
         val cnt = mToBeDeleted.size
-        val eventIDs = arrayOfNulls<String>(cnt)
+        val eventIDs = arrayOf<String>()
         for (i in 0..cnt - 1) {
             eventIDs[i] = mToBeDeleted[i].toString()
         }
@@ -225,11 +226,10 @@ class DayFragment : Fragment(), DBHelper.DBOperationsListener, AdapterView.OnIte
         editEvent(getEventsToShow(mEvents!!)[position])
     }
 
-    override fun eventInserted(event: Event?) {
+    override fun eventInserted(event: Event) {
-
     }
 
-    override fun eventUpdated(event: Event?) {
+    override fun eventUpdated(event: Event) {
 
     }