2.数据初始化

读取type数据将其载入combox，同时对自定义的信号进行绑定

void Widget::InitData() {     QString sel1 = "select name from type";         QSqlQuery query(db);     query.exec(sel1);     QStringList listName;     while(query.next())     {         listName<cbox_type->addItems(listName);      cbox_select_type->addItems(listName);     connect(cbox_select_type,SIGNAL(currentTextChanged(QString))             ,this,SLOT(on_cbox_type_currentTextChanged(QString)));     connect(btn_select_select,SIGNAL(clicked(bool)),this,SLOT(doProcessClickSelect(bool))); }

3.设定按钮功能

将各个按钮进行槽功能绑定，分别对应隐藏和显示不同的界面，以商品入库和信息查询界面为例

void Widget::on_btn_storage_clicked() {     wid_select->hide();     wid_password->hide();     ui->wid_sell->show();     ui->lbl_sell->setText("商品入库"); }

void Widget::on_btn_select_clicked() {     ui->wid_sell->hide();     wid_password->hide();     wid_select->show();     ui->lbl_sell->setText("商品查询"); }

4.商品查询功能

商品查询功能通过商品的品牌和类型对已存商品进行查询

从ui控件中的combox处获取值并加入SQL语句中

QString sel2 = QString("select * from brand where name = '%1' and type='%2'")             .arg(cbox_select_brand->currentText())             .arg(cbox_select_type->currentText());

然后通过append在文本框进行显示信息

query.exec(sel2);     QString msg;     while(query.next())     {        msg+= "品牌名称："+query.value(1).toString()+"\n";        msg+= "商品类型："+query.value(2).toString()+"\n";        msg+= "商品价格："+query.value(3).toString()+"\n";        msg+= "商品总数："+query.value(4).toString()+"\n";        msg+= "售出数量："+query.value(5).toString()+"\n";        msg+= "剩余数量："+query.value(6).toString()+"\n";     }     tedit_select_show->append(msg);

结果如下：

5.类型选择信号的接收

由于初始化只进行了类型的读取，为了使类型和品牌进行联动，定义一个combox中选项改变的信号传入槽中，对选中的类型进行SQL查询并添加到品牌的combox进行显示

void Widget::on_cbox_type_currentTextChanged(const QString &arg1) {     QSqlQuery query(db);     QString sel2 = QString("select name from brand where type = '%1'").arg(arg1);     query.exec(sel2);     QStringList listProduct;     while(query.next())     {         listProduct<cbox_brand->clear();     ui->cbox_brand->addItems(listProduct);     cbox_select_brand->clear();     cbox_select_brand->addItems(listProduct); }

6.商品添加

当点击商品添加的确定按钮时，要对添加的数据进行接收，并通过SQL语句将其传入数据库中，此处可以采用prepare方法，将SQL语句写入prepare方法中，需要替换的数据前面加上"："，并通过bindValue()方法进行替换。

if(text == "商品添加")     {         int maxNum = 0;         QSqlQuery query(db);         QString cmd = "select max(id2) from brand";         query.exec(cmd);         if(query.next())         {             maxNum = query.value(0).toString().toInt();             maxNum += 1;             query.prepare("INSERT INTO brand (id2, name, type,price,sum,sell,last) VALUES (:id2, :name, :type,:price,:sum,:sell,:last)");             query.bindValue(":id2", maxNum);             query.bindValue(":name", ui->cbox_brand->currentText());             query.bindValue(":type", ui->cbox_type->currentText());             query.bindValue(":price", ui->ledit_price->text());             query.bindValue(":sum", ui->sbox_num->text());             query.bindValue(":sell", ui->sbox_num->text());             query.bindValue(":last", ui->sbox_num->text());             bool ret = query.exec();             if(ret)             {                 QMessageBox::information(this,"提示","保存成功",QMessageBox::Ok);             }             else             {                 QMessageBox::information(this,"提示","保存失败",QMessageBox::Ok);             }         }         else         {             return;         }     }

7.商品入库

商品入库功能主要是对已经在库的商品进行数量上的操作，因此通过SQL中的UPDATE进行相对应的操作，同样使用prepare方法，因为入库需要查询相对应的商品，因此通过类型、品牌、价格进行查询判断，并记录下商品的id，未查询到提示用户先进行商品添加。

if(text == "商品入库")     {         int id = 0;         int sum = 0;         int last = 0;         QSqlQuery query(db);         QString type = ui->cbox_type->currentText();         QString brand = ui->cbox_brand->currentText();         QString price = ui->ledit_price->text();         QString cmd = QString("select id2,sum,last from brand where type = '%1' and name = '%2' and price = '%3'").arg(type).arg(brand).arg(price);         query.exec(cmd);         if(query.next())         {             id = query.value(0).toInt();             sum = query.value(1).toInt();             last = query.value(2).toInt();             sum += ui->sbox_num->text().toUInt();             last += ui->sbox_num->text().toUInt();             query.prepare("UPDATE brand SET sum = :sum,last = :last WHERE id2 = :id");             query.bindValue(":sum", sum);             query.bindValue(":last", last);             query.bindValue(":id", id);             bool ret = query.exec();             if(ret)             {                 QMessageBox::information(this,"提示","入库成功",QMessageBox::Ok);              }             else             {                 QMessageBox::information(this,"提示","入库失败",QMessageBox::Ok);             }          }         else         {             QMessageBox::information(this,"错误","未找到商品",QMessageBox::Ok);         }     }

8.出售商品

出售商品与商品入库操作相似，主要是对已售出商品数量和剩余商品数量进行对应的操作，通过查询商品剩余数量对售出数量进行相应的操作，提示用户商品是否缺货。

if(text == "出售商品")     {         int id,sum,sell,last = 0;         QSqlQuery query(db);         QString type = ui->cbox_type->currentText();         QString brand = ui->cbox_brand->currentText();         QString price = ui->ledit_price->text();         QString cmd = QString("select id2,sum,sell,last from brand where type = '%1' and name = '%2' and price = '%3'").arg(type).arg(brand).arg(price);         bool ret = query.exec(cmd);         if(query.next())         {             id = query.value(0).toInt();             sum = query.value(1).toInt();             sell = query.value(2).toInt();             last = query.value(3).toInt();             if(last>0)             {                 int last1 = ui->sbox_num->text().toUInt();                 sell += ui->sbox_num->text().toUInt();                 if(last>=last1)                 {                     last -= ui->sbox_num->text().toUInt();                     query.prepare("update brand set sell = :sell,last = :last where id2 = :id2");                     query.bindValue(":sell",sell);                     query.bindValue(":last",last);                     query.bindValue(":id2",id);                     bool ret = query.exec();                     if(ret)                     {                         QMessageBox::information(this,"提示","售出成功",QMessageBox::Ok);                     }                     else                     {                          QMessageBox::information(this,"提示","售出失败",QMessageBox::Ok);                     }                 }                 else                 {                     QMessageBox::information(this,"提示","商品缺货",QMessageBox::Ok);                 }             }             else             {                 QMessageBox::information(this,"提示","商品缺货",QMessageBox::Ok);             }         }     }