SQLiteDatabase sqLiteDatabase = Helper.getWritableDatabase();

When I write this statement SQLiteDatabase sqLiteDatabase = sarahHelper.getWritableDatabase(); to oncreate method of Mainactivity, application stops running

public class MainActivity extends Activity {
SarahHelper sarahHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Helper = new Helper(this);
   // SQLiteDatabase sqLiteDatabase = Helper.getWritableDatabase();

}

public class Helper extends SQLiteOpenHelper {

private static final String DATABASE_NAME = "mmh";
private static final String TABLE_NAME = "mytable";
private static final int DATABASE_VERSION = 1;
private static final String UID = "_name";
private static final String PRO = "proximity";
private static final String CREATE_TABLE = "CREATE TABLE "+TABLE_NAME+" ("+UID+" INTEGER PRIMARY KEY, "+PRO+" VARCHAR(255));";
private static final String DROP_TABLE = "DROP_TABLE"+TABLE_NAME+"IF  EXISTS" ;

private Context context;


//context, database name,
public Helper(Context context) {
    super(context,DATABASE_NAME, null, DATABASE_VERSION);
    this.context= context;
    message.Message(context, "constructor called");
}

@Override
public void onCreate(SQLiteDatabase db) {
    try {

        db.execSQL(CREATE_TABLE);
        message.Message(context, "OnCreate called");
    }catch (SQLException e)
    {
        message.Message(context, "" + e);
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

   try {
       db.execSQL(DROP_TABLE);
       onCreate(db);
   }catch (SQLException e)
   {
       message.Message(context,""+e );
   }

}
}

message is other class, no syntax error just when i include stated statement it just stops running, when i removed i works and only constructor method called not oncreate