How to retrieve existing number from column and update it

I am trying to make this simple app which calculates likes. Every-time you click on like button, it updates the counter in DB. The problem is, when I click it 5 times in one session, close and open again, it starts from 1 instead of 6 and shows 1,2,3,4,5,1. The value is lost once the session ends. I want it to be 6 and continue. How can I retrieve values from Database. Also, the rows are increasing. I want it to update the count in a single row and not add a new row every time I click the button.

This is my Main Activity:

public class MainActivity extends AppCompatActivity {
//declare
TextView showCounts;
MyDBHandler dbHandler;
Calculate obj;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //initialize objects
    showCounts = (TextView) findViewById(R.id.showCounts);
    dbHandler = new MyDBHandler(this, null, null, 1);
    obj = new Calculate();

}

public void likeButtonClicked(View view) //when like button is clicked
{
    obj.set_likes(1); //clicked 1 time
    boolean isLiked = dbHandler.incrementLikes(); //increment like in database
    printDatabase(); //show db
    if(isLiked) { //if like goes into db
        Toast.makeText(MainActivity.this, "Liked successfully", Toast.LENGTH_LONG).show();
    }
    else
        Toast.makeText(MainActivity.this, "Error", Toast.LENGTH_LONG).show();
}

public void dislikeButtonClicked(View view)//dislike button is clicked
{
    obj.set_dislikes(1);
    boolean isInserted = dbHandler.incrementDislikes();
    printDatabase();
    if (isInserted) {
        Toast.makeText(MainActivity.this, "Added successfully", Toast.LENGTH_LONG).show();
    } else
        Toast.makeText(MainActivity.this, "Error", Toast.LENGTH_LONG).show();
}

// print database
public void printDatabase()
{
    Cursor res = dbHandler.dbToString();
    if(res.getCount() == 0) //if table is empty
    {
        showCounts.setText("Error Nothing Found!");
        return;
    }

    StringBuffer str = new StringBuffer(); //if not empty
    while(res.moveToNext())
    {
        str.append("Likes: "+res.getString(0)+"\n");
    }
    showCounts.setText(str.toString()); //display database in textview
}

This is my Calculate class which has getters and setters:

public class Calculate {
private static int _likes;
private static int _dislikes;

public Calculate() 
{    }

public int get_likes() {
    return this._likes;
}

public void set_likes(int likes) {
    _likes += likes;

}

public int get_dislikes() {
    return this._dislikes;
}

public void set_dislikes(int dislikes) {
    _dislikes += dislikes;
} }//class ends

This is my DBHandler

public class MyDBHandler extends SQLiteOpenHelper{
//Declarations
private static final int DATABASE_VERSION = 4; 
private static final String DATABASE_NAME = "likeCalci.db";
public static final String TABLE_LIKECALCULATOR = "likeCalculator";
public static final String COLUMN_LIKE = "_likes";
public static final String COLUMN_DISLIKE = "_dislikes";
int like_count = 0;
int dislike_count = 0;

//Constructor
public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db)
{
    //create table
    String query = "CREATE TABLE " + TABLE_LIKECALCULATOR + "("+
            COLUMN_LIKE + " INTEGER " + COLUMN_DISLIKE + " INTEGER " + ");";
    db.execSQL(query);
}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) //upgrade db
{
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_LIKECALCULATOR);
    onCreate(db);
}

//call when like button is clicked
public boolean incrementLikes()
{
    Calculate obj = new Calculate(); //obj
    like_count = obj.get_likes(); //get number of likes and store it
    ContentValues values = new ContentValues(); 
    values.put(COLUMN_LIKE, like_count); //put values in column
    SQLiteDatabase db = getWritableDatabase();
    long result = db.insert(TABLE_LIKECALCULATOR, null, values); //insert likes in db
    db.close();
    if(result == -1) //if insert is unsuccessful
        return false;
    else //if insert is successful
        return true;
}

public boolean incrementDislikes()
{
    Calculate obj = new Calculate();
    dislike_count = obj.get_dislikes();
    ContentValues values = new ContentValues();
    values.put(COLUMN_DISLIKE, dislike_count);
    SQLiteDatabase db = getWritableDatabase();
    long result = db.insert(TABLE_LIKECALCULATOR, null, values);
    db.close();
    if(result == -1)
        return false;
    else
        return true;
}

//print database
public Cursor dbToString() 
{
  SQLiteDatabase db  = this.getWritableDatabase();
    Cursor res = db.rawQuery("select * from "+TABLE_LIKECALCULATOR,null);
    return res;
}} //Class dbhandler ends

This is how the program runs: http://ift.tt/1R1vfrr

The dislike column is also not created. I started learning android few days back and this is taking a lot of time. Any times while dealing with Databases?