Qt SQL连接即使在删除后仍处于打开状态
第二次尝试连接到数据库时,我收到以下消息:Qt SQL连接即使在删除后仍处于打开状态,qt,qt4,Qt,Qt4,第二次尝试连接到数据库时,我收到以下消息: QSqlDatabasePrivate::removeDatabase: connection 'CompanyDatabase' is still in use, all queries will cease to work. 我删除了以前使用过的模型,删除了所有连接,并关闭了数据库。下面,我将打开CompanyWidget的小部件作为一个模式对话框,因为我认为它可能与我如何打开/关闭使用数据库的小部件有关。有人能解释一下为什么这个数据库还在使用吗
QSqlDatabasePrivate::removeDatabase: connection 'CompanyDatabase' is still in use, all queries will cease to work.
我删除了以前使用过的模型,删除了所有连接,并关闭了数据库。下面,我将打开CompanyWidget的小部件作为一个模式对话框,因为我认为它可能与我如何打开/关闭使用数据库的小部件有关。有人能解释一下为什么这个数据库还在使用吗
编辑:如果我将QSQLDABASE成员更改为指针并使用以下方法创建它:
this->CompanyDatabase = new QSqlDatabase(QSqlDatabase::addDatabase("QSQLITE", "CompanyDatabase"));
并在重新添加数据库之前将其删除:
if(this->CompanyDatabase)
{
delete this->CompanyDatabase;
this->CompanyDatabase = NULL;
}
然后错误消失了。为什么这与我处理非指针成员的方式有什么不同
编辑公司Widget.h
#ifndef EditCompanyWidget_H
#define EditCompanyWidget_H
#include "ui_EditCompanyWidget.h"
#include <QDialog>
#include <QSqlDatabase>
class QSqlTableModel;
class EditCompanyWidget : public QDialog, private Ui::EditCompanyWidget
{
Q_OBJECT
public:
EditCompanyWidget(QSqlDatabase);
~EditCompanyWidget();
public slots:
void on_btnExit_clicked();
protected:
QSqlTableModel* Model;
};
#endif
EditCompanyWidget.cpp
#include "EditCompanyWidget.h"
#include <iostream>
#include <QSqlDatabase>
#include <QStringList>
#include <QSqlQuery>
#include <QDebug>
#include <QSqlError>
#include <QVariant>
#include <QSqlTableModel>
#include <QSqlRecord>
EditCompanyWidget::EditCompanyWidget(QSqlDatabase database) : QDialog(NULL)
{
setupUi(this);
//QSqlTableModel* model = new QSqlTableModel;
this->Model = new QSqlTableModel(NULL, database);
this->Model->setTable("CompanyTable");
this->Model->setEditStrategy(QSqlTableModel::OnManualSubmit);
//model->setFilter(QString("id=%1").arg(1));
this->Model->select();
this->tableView->setModel(this->Model);
}
EditCompanyWidget::~EditCompanyWidget()
{
if(this->Model)
{
std::cout << "destructor Deleting..." << std::endl;
delete this->Model;
this->Model = NULL;
}
}
void EditCompanyWidget::on_btnExit_clicked()
{
this->Model->revertAll();
if(this->Model)
{
std::cout << "btnExit Deleting..." << std::endl;
delete this->Model;
this->Model = NULL;
}
//this->setResult(QDialog::Rejected);
this->reject();
}
#include "TimeTrackerConfigurationWidget.h"
#include "EditCompanyWidget.h"
#include <iostream>
#include <QSqlDatabase>
#include <QFileDialog>
#include <QSqlError>
#include <QSqlQuery>
TimeTrackerConfigurationWidget::TimeTrackerConfigurationWidget(QWidget *parent) : QMainWindow(parent)
{
setupUi(this);
}
void TimeTrackerConfigurationWidget::on_btnEditCompany_clicked()
{
// QString fileName = QFileDialog::getOpenFileName(this, "Database File", ".", "Image Files (*.sqlite)");
//
// if(fileName.toStdString().empty())
// {
// std::cout << "Filename was empty." << std::endl;
// return;
// }
QString fileName = "test.sqlite";
if(!QFile::exists(fileName))
{
std::cerr << "File does not exist!" << std::endl;
return;
}
this->CompanyDatabase.close();
//QSqlDatabase::removeDatabase("CompanyDatabase");
//QSqlDatabase database = QSqlDatabase::addDatabase("QSQLITE");
// Delete all connections
for(unsigned int i = 0; i < QSqlDatabase::connectionNames().size(); ++i)
{
//QSqlDatabase::removeDatabase("TestConnection");
QSqlDatabase::removeDatabase(QSqlDatabase::connectionNames()[i]);
}
this->CompanyDatabase = QSqlDatabase::addDatabase("QSQLITE", "CompanyDatabase");
//this->CompanyDatabase = QSqlDatabase::addDatabase("QSQLITE");
this->CompanyDatabase.setDatabaseName(fileName);
if (!this->CompanyDatabase.open())
{
std::cerr << "Could not open database" << std::endl;
std::cerr << this->CompanyDatabase.lastError().text().toStdString() << std::endl;
return;
}
EditCompanyWidget* editCompanyWidget = new EditCompanyWidget(this->CompanyDatabase);
editCompanyWidget->exec();
delete editCompanyWidget;
}
MainWidget.h
#ifndef TimeTrackerConfigurationWidget_H
#define TimeTrackerConfigurationWidget_H
#include "ui_TimeTrackerConfigurationWidget.h"
#include <QMainWindow>
#include <QSqlDatabase>
class TimeTrackerConfigurationWidget : public QMainWindow, private Ui::TimeTrackerConfigurationWidget
{
Q_OBJECT
public:
TimeTrackerConfigurationWidget(QWidget *parent = 0);
public slots:
void on_btnNewCompany_clicked();
void on_btnEditCompany_clicked();
protected:
QSqlDatabase CompanyDatabase;
};
#endif
MainWidget.cpp
#include "EditCompanyWidget.h"
#include <iostream>
#include <QSqlDatabase>
#include <QStringList>
#include <QSqlQuery>
#include <QDebug>
#include <QSqlError>
#include <QVariant>
#include <QSqlTableModel>
#include <QSqlRecord>
EditCompanyWidget::EditCompanyWidget(QSqlDatabase database) : QDialog(NULL)
{
setupUi(this);
//QSqlTableModel* model = new QSqlTableModel;
this->Model = new QSqlTableModel(NULL, database);
this->Model->setTable("CompanyTable");
this->Model->setEditStrategy(QSqlTableModel::OnManualSubmit);
//model->setFilter(QString("id=%1").arg(1));
this->Model->select();
this->tableView->setModel(this->Model);
}
EditCompanyWidget::~EditCompanyWidget()
{
if(this->Model)
{
std::cout << "destructor Deleting..." << std::endl;
delete this->Model;
this->Model = NULL;
}
}
void EditCompanyWidget::on_btnExit_clicked()
{
this->Model->revertAll();
if(this->Model)
{
std::cout << "btnExit Deleting..." << std::endl;
delete this->Model;
this->Model = NULL;
}
//this->setResult(QDialog::Rejected);
this->reject();
}
#include "TimeTrackerConfigurationWidget.h"
#include "EditCompanyWidget.h"
#include <iostream>
#include <QSqlDatabase>
#include <QFileDialog>
#include <QSqlError>
#include <QSqlQuery>
TimeTrackerConfigurationWidget::TimeTrackerConfigurationWidget(QWidget *parent) : QMainWindow(parent)
{
setupUi(this);
}
void TimeTrackerConfigurationWidget::on_btnEditCompany_clicked()
{
// QString fileName = QFileDialog::getOpenFileName(this, "Database File", ".", "Image Files (*.sqlite)");
//
// if(fileName.toStdString().empty())
// {
// std::cout << "Filename was empty." << std::endl;
// return;
// }
QString fileName = "test.sqlite";
if(!QFile::exists(fileName))
{
std::cerr << "File does not exist!" << std::endl;
return;
}
this->CompanyDatabase.close();
//QSqlDatabase::removeDatabase("CompanyDatabase");
//QSqlDatabase database = QSqlDatabase::addDatabase("QSQLITE");
// Delete all connections
for(unsigned int i = 0; i < QSqlDatabase::connectionNames().size(); ++i)
{
//QSqlDatabase::removeDatabase("TestConnection");
QSqlDatabase::removeDatabase(QSqlDatabase::connectionNames()[i]);
}
this->CompanyDatabase = QSqlDatabase::addDatabase("QSQLITE", "CompanyDatabase");
//this->CompanyDatabase = QSqlDatabase::addDatabase("QSQLITE");
this->CompanyDatabase.setDatabaseName(fileName);
if (!this->CompanyDatabase.open())
{
std::cerr << "Could not open database" << std::endl;
std::cerr << this->CompanyDatabase.lastError().text().toStdString() << std::endl;
return;
}
EditCompanyWidget* editCompanyWidget = new EditCompanyWidget(this->CompanyDatabase);
editCompanyWidget->exec();
delete editCompanyWidget;
}
文件中明确指出:。在删除连接之前,必须销毁所有已实例化的查询对象和QSqlDatabase连接对象。当您删除指针时,实际上就是这样做的。对于您以前的代码,您没有这样做。对不起,我弄错了,我的badIt看起来非常奇怪,尽管您不能将对象保留为成员变量,然后对其调用某种断开连接函数来模拟删除它?这是一个问题还是一个陈述?对不起,我不知道有没有办法,但我认为没有必要。通过使用静态QSqlDatabase::database。。。你想做什么就做什么。也可以使用重写操作符=你可以分配给对象,而不是复制,我猜,所以没有开销。考虑一下这个错误。到处都有人问它,这里也有关于堆栈溢出的问题。您可能会找到更多信息。我想我不明白为什么必须使用静态函数添加和删除连接。如果您只需要使用诸如ConnectionObject myConnection=SqlDatabase之类的东西来控制连接,不是会容易得多吗?好吧,这取决于你。我觉得这样很好。但是你看过我最后的评论了吗?你就是这么做的。您添加了数据库。。要使用名称创建连接,您可以稍后使用数据库检索连接对象。。。方法:QSqlDatabase myConnection=QSqlDatabase::databaseconnectionName。。。您可以使用removeConnection删除连接。这怎么可能更简单呢?所有这些都在文档中用代码片段清楚地说明了。