简易点菜系统

//main.cpp
#include "mywin.h"
#include "foodtype.h"
#include <QApplication>
#include <QSqlDatabase>
#include <QDebug>
#include <QSqlDriver>
#include <QSqlQuery>
#include <QMessageBox>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
   // QSqlDatabase db;
    QSqlDatabase db=QSqlDatabase::addDatabase("QMYSQL");//数据库必须在声明的时候指定，否则会出错
    qDebug()<< db.drivers();//查看支持的数据库
    //db.addDatabase("QMYSQL");
    db.setDatabaseName("mydb");
    db.setHostName("192.168.2.90");
    db.setUserName("who");
    db.setPassword("123456");
    if(!db.open())
    {
        QMessageBox::critical(0,"error","open databases failed");
        exit(0);
    }
    qDebug()<<db.tables();


    QSqlQuery query;
    query.exec("select *from foodtype;");
    while(query.next())
    {
        qDebug()<<query.value(0).toInt();//转化一下，要不会把数据类型一块打印出来
        qDebug()<<query.value(1).toString();
    }

    qDebug()<<query.exec("show tables;");
    MyWin w;
    w.show();

    FoodType foodtype;
    foodtype.show();
    return a.exec();
}

//mywin.cpp
#include "mywin.h"
#include "ui_mywin.h"
#include <QSqlQuery>
#include <QDebug>
#include <QMessageBox>
#include <QString>

MyWin::MyWin(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::MyWin)
{
    ui->setupUi(this);

    QSqlQuery query;
    query.exec("select *from foodtype;");
    while(query.next())
    {
       // ui->comboBox->addItem(query.value(0).toInt(),query.value(1).toString());//将菜系添加到下拉列表中,必须在后面加上为数据项
                                                 //，要不后面无法获取fid的下标；
        ui->comboBox->addItem(query.value(1).toString(),query.value(0).toInt());
    }
}

MyWin::~MyWin()
{
    delete ui;
}

void MyWin::on_pushButton_2_clicked()
{
    this->close();
}

void MyWin::on_pushButton_clicked()
{
   QSqlQuery query;
   int fid=ui->comboBox->currentData().toInt();//获取下拉列表里的数据值
    //qDebug()<<fid;
   if(ui->line_id->text().isEmpty())
   {
       QMessageBox::critical(this,"error","please input id");
       ui->line_id->setFocus();//聚焦光标
       return;//exit current function
   }

   if(ui->line_name->text().isEmpty())
   {
       QMessageBox::critical(this,"error","please input name");
       ui->line_name->setFocus();//聚焦光标
       return;
   }
   if(ui->line_price->text().isEmpty())
   {
       QMessageBox::critical(this,"error","please input price");
       ui->line_price->setFocus();//聚焦光标
       return;
   }
   //int id=ui->line_id->text().toInt(); //用Qstring 类型声明id，要不下面打印id号时会报错
   QString id=ui->line_id->text();
   QString str2("select *from food where fid=%1;");
   qDebug()<< query.exec(str2.arg(id));
   while(query.next())
   {
       QMessageBox::critical(this,"error","id" + id + "used");
       ui->line_id->setFocus();
       return;
   }

   QMessageBox mesgBox(this);
   mesgBox.setText("The document has been modified.");
   mesgBox.setInformativeText("Do you want to save you change?");
   mesgBox.setStandardButtons(QMessageBox::Save | QMessageBox::Cancel |QMessageBox::Discard);
   int ret=mesgBox.exec();

   QString name=ui->line_name->text();
   float price=ui->line_price->text().toFloat();
   QString mem =ui->textEdit->document()->toPlainText();//多行编辑的显示

   QString str("insert into food values(%1,'%2',%3,%4,'%5');");
   switch(ret){
        case QMessageBox::Save:
                query.exec(str.arg(id).arg(name).arg(fid).arg(price).arg(mem));
                break;
        case QMessageBox::Cancel:
               // return;
                break;
       case QMessageBox::Discard:
                ui->line_id->setText(" ");
                return;
                break;
   }
}

  //显示tableview里的数据时，要用到《QsqlQueryModel》,
　   #include "ui_foodtype.h"
//#include <QSqlTableModel>
#include <QSqlQueryModel>

FoodType::FoodType(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::FoodType)
{
    ui->setupUi(this);
    QSqlQueryModel *model=new QSqlQueryModel(this);
   // model->setTable("菜单信息");
    model->setQuery("select fid,food.name,ftypeid,fprice,id,foodtype.name,mem from food inner join foodtype on id=fid;");

    ui->tableView->setModel(model);
}

FoodType::~FoodType()
{
    delete ui;
}