数据库文件被锁定（数据库被锁定）？

Question

我正在更新，删除和创建日历中的事件。我有很多方法。但是，如果我尝试运行其中任何一个，它会给我SQLITE BUSY错误。我在每种方法后都关闭了连接。那可能是什么问题呢？我知道我有太多关系，但我确实关闭了它们。

    public static DatabaseConnection db = new DatabaseConnection();

public static ArrayList<EventModel> retrieveAllInfo() {
    ArrayList<EventModel> listOfEvents = new ArrayList<EventModel>();

    ResultSet rs = null;

    String dbQuery;

    db.getConnection();
    dbQuery = "SELECT * FROM ToDoList";

    rs = db.readRequest(dbQuery);
    try {
        while (rs.next()) {
            EventModel model = new EventModel(); 
            model.setId(rs.getInt("id"));
            model.setEventName(rs.getString("eventName"));
            model.setDate(rs.getString("day"));
            model.setTime(rs.getString("time"));
            listOfEvents.add(model);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

    db.terminate(); 
    return listOfEvents;
}

public static boolean updateEvent(EventModel eventmodel) {
    //declare local variables
    boolean success = false;
    String dbQuery; 
    PreparedStatement pstmt;

    db.getConnection();     

    dbQuery = "UPDATE ToDoList SET eventName = ?, time = ?, day = ? WHERE id = " + eventmodel.getId();
    pstmt = db.getPreparedStatement(dbQuery);

    try {
        pstmt.setString(1, eventmodel.getEventName());
        pstmt.setString(2, eventmodel.getTime());
        pstmt.setString(3, eventmodel.getDate());
        if (pstmt.executeUpdate() == 1)
            success = true;
        pstmt.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

    db.terminate();

    return success;
 }