qt mysql 分页

最近看到关于qt 中mysql 浏览数据分页，有人用到了qtablewidget 翻页时手动添加

就在想，既然qt中提供了view和model，为什么放着不用哪？

简单实现了一把，记录一下

首先重新继承一下QSqlTableModel，翻页时修改记录数

userSqlTableModel.h

#ifndef USERSQLTABLEMODEL_H
#define USERSQLTABLEMODEL_H

#include <QSqlTableModel>

class UserSqlTableModel : public QSqlTableModel
{
    Q_OBJECT
public:
    explicit UserSqlTableModel(QObject *parent = 0,QSqlDatabase db = QSqlDatabase() );

    void setStart(int start){this->m_nStart = start;}
    int getStart(){return this->m_nStart;}
public:
    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
private:
    int m_nStart;   //记录数据起始id
};

#endif // USERSQLTABLEMODEL_H

userSqlTableModel.cpp

#include "usersqltablemodel.h"

UserSqlTableModel::UserSqlTableModel(QObject *parent,QSqlDatabase db) :
    QSqlTableModel(parent,db)
{
    m_nStart = 0;
}
QVariant UserSqlTableModel::headerData(int section, Qt::Orientation orient, int role) const
{
  if (orient == Qt::Vertical && role == Qt::DisplayRole)
    return section + m_nStart;

  return QSqlTableModel::headerData(section,orient,role);
}

在对话框类中声明几个变量:

private:
    UserSqlTableModel *userModel;


    int m_nTotal;           //总记录数
    int m_nPageSize;        //每页显示条数
    int m_nCurPageSize;     //当前页数据条数
    int m_nStart;           //起始记录数

初始化变量:

    this->m_nStart = -1;
    this->m_nPageSize = 6;
    this->m_nCurPageSize = 0;
    this->m_nTotal = 0;

    userModel = new UserSqlTableModel(this);
    userModel->setTable("user");
    userModel->setSort(User_Name, Qt::AscendingOrder);
    userModel->setHeaderData(User_Name, Qt::Horizontal,tr("账 号"));
    userModel->setHeaderData(User_GroupChName, Qt::Horizontal,tr("所属组"));
    userModel->setHeaderData(User_Description,Qt::Horizontal, tr("备注"));
    

    userView->setModel(userModel);
    userView->setSelectionMode(QAbstractItemView::SingleSelection);
    userView->setSelectionBehavior(QAbstractItemView::SelectRows);
    userView->setColumnHidden(User_Id, true);
    userView->setColumnHidden(User_Pwd, true);
    userView->setColumnHidden(User_Group, true);
    userView->resizeColumnsToContents();
    userView->horizontalHeader()->setStretchLastSection(true);
    
    this->m_nTotal = this->getTotal();
    on_pushButton_first_clicked();

翻页槽：

void UserDialog::on_pushButton_first_clicked() //首页
{
    if(this->m_nStart == 0 && this->m_nCurPageSize == this->m_nPageSize)
        return;

    this->m_nStart = 0;
    this->m_nCurPageSize = this->m_nTotal > this->m_nPageSize ? this->m_nPageSize : this->m_nTotal;

    updateInfo();
}

void UserDialog::on_pushButton_previous_clicked() //上一页
{
    if(this->m_nStart == 0 || this->m_nTotal <= 0)
        return;

    this->m_nStart -= this->m_nPageSize;
    this->m_nCurPageSize = this->m_nPageSize;

    updateInfo();
}

void UserDialog::on_pushButton_next_clicked() //下一页
{
    if(this->m_nCurPageSize < this->m_nPageSize || this->m_nTotal <= 0)
        return;

    this->m_nStart += this->m_nPageSize;
    this->m_nCurPageSize = this->m_nTotal - this->m_nStart > this->m_nPageSize ? this->m_nPageSize : this->m_nTotal - this->m_nStart;

    updateInfo();
}

void UserDialog::on_pushButton_last_clicked()   //尾页
{
    if(this->m_nCurPageSize < this->m_nPageSize || this->m_nTotal <= 0)
        return;

    this->m_nCurPageSize = this->m_nTotal % this->m_nPageSize;
    this->m_nStart = this->m_nTotal - this->m_nCurPageSize;

    updateInfo();
}

void UserDialog::updateInfo()
{
    QString strFilter = QString(" 1=1 limit %1,%2").arg(this->m_nStart).arg(this->m_nCurPageSize);
    userModel->setStart(this->m_nStart + 1);
    userModel->setFilter(strFilter);
    userModel->select();
}

总结来关键的就有两点:

1、重载QSqlTableModel，在翻页时重置记录条数

         2、设置model的过滤条件

当时直接  setFilter("limit 0,1;")始终不行 ，但是直接执行带limit 的 sql 语句就没有问题。

最终在手册中看到这样一句话

The filter is a SQL WHERE clause without the keyword WHERE (for example, name='Josephine').

就是说过滤条件即为省略where的条件语句

select * from table where limit 0,6; 肯定是不行的

加一个永真条件就哦了

同时注意一下最后的‘;’若没有用qt 2.3.0会报执行时错误:

D:\qt\1010\tengxun\fontsampler-build-desktop\debug\fontsampler.exe 启动中...

ASSERT: "idx >= 0 && idx < s" in file ..\..\include/QtCore/../../../../../../ndk_buildrepos/qt-desktop/src/corelib/tools/qvarlengtharray.h, line 107