Question

这是我的databaseconnection.h类

#ifndef DATABASECONNECTION_H
#define DATABASECONNECTION_H
#include <QtSql>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlDriver>
#include <QtSql/QSqlQuery>



class DatabaseConnection
{
public:
    DatabaseConnection();
    bool dbConOpen();
    void dbConClose();
    QSqlDatabase db;



};

#endif // DATABASECONNECTION_H

databaseconnection.cpp

#include <QtSql>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlDriver>
#include <QtSql/QSqlQuery>
#include <QDebug>

#include "databaseconnection.h"

DatabaseConnection::DatabaseConnection()
{

}

bool DatabaseConnection :: dbConOpen()
{
    db = QSqlDatabase ::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setDatabaseName("lms");
    db.setUserName("root");
    db.setPassword("");
    if(!db.open())
    {

    return false;

    }
    else

        return true;


}
void DatabaseConnection :: dbConClose()
{
    QString connection = db.connectionName();
    db.close();
    db = QSqlDatabase();
    db.removeDatabase(connection);
}

fictionsection类通过materials.h类继承数据库类。然后我通过点击fictionsection.cpp类中的按钮将表记录加载到qtableview，如下所示

void FictionSection::on_btnLoad_clicked()
{
    DatabaseConnection mydb;
        mydb.dbConOpen();

       //Loading fiction table values to a table

       QSqlQueryModel *modl = new QSqlQueryModel();


       QSqlQuery *query = new QSqlQuery(mydb.db) ;
       query->prepare(" select * from fiction");
     bool flag = query->exec();

     //assigning the values to a QTableView
     if(flag == true)
     {
         modl->setQuery(*query);
         ui->tblFiction->setModel(modl);
          ui->tblFiction->show();


     }
    dbConClose();

}

项目运行时，它会显示以下消息。但该项目完全符合我的要求。

QSqlDatabasePrivate::removeDatabase: connection 'qt_sql_default_connection' is still in use, all queries will cease to work.
QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

请帮我解决这个问题，并且由于此消息有任何不良影响。因为我计划在完成整个实施后在Ubuntu中运行我的项目。目前我使用的是Windows操作系统。

Answer 1

由于不必要地打开和关闭数据库连接，显示此消息。最终代码应如下所示。

void FictionSection::on_btnLoad_clicked()
{
    DatabaseConnection mydb;


       //Loading fiction table values to a table

       QSqlQueryModel *modl = new QSqlQueryModel();


       QSqlQuery *query = new QSqlQuery(mydb.db) ;
       query->prepare(" select * from fiction");
     bool flag = query->exec();

     //assigning the values to a QTableView
     if(flag == true)
     {
         modl->setQuery(*query);
         ui->tblFiction->setModel(modl);
          ui->tblFiction->show();


     }


}

重复的数据库连接qt

1 个答案: