9、Qt Project之简单的数据库接口

简单的数据库接口

 Step1：首先完成整个UI界面的额设计：

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>400</width>
    <height>313</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <widget class="QPushButton" name="pushButton">
    <property name="geometry">
     <rect>
      <x>320</x>
      <y>220</y>
      <width>51</width>
      <height>27</height>
     </rect>
    </property>
    <property name="text">
     <string>Insert</string>
    </property>
   </widget>
   <widget class="QTextEdit" name="textEdit">
    <property name="geometry">
     <rect>
      <x>80</x>
      <y>220</y>
      <width>51</width>
      <height>31</height>
     </rect>
    </property>
   </widget>
   <widget class="QTextEdit" name="textEdit_2">
    <property name="geometry">
     <rect>
      <x>140</x>
      <y>220</y>
      <width>101</width>
      <height>31</height>
     </rect>
    </property>
   </widget>
   <widget class="QTextEdit" name="textEdit_3">
    <property name="geometry">
     <rect>
      <x>250</x>
      <y>220</y>
      <width>61</width>
      <height>31</height>
     </rect>
    </property>
   </widget>
   <widget class="QLabel" name="label">
    <property name="geometry">
     <rect>
      <x>100</x>
      <y>200</y>
      <width>31</width>
      <height>17</height>
     </rect>
    </property>
    <property name="text">
     <string>ID</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_2">
    <property name="geometry">
     <rect>
      <x>170</x>
      <y>200</y>
      <width>65</width>
      <height>17</height>
     </rect>
    </property>
    <property name="text">
     <string>NAME</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_3">
    <property name="geometry">
     <rect>
      <x>260</x>
      <y>200</y>
      <width>65</width>
      <height>17</height>
     </rect>
    </property>
    <property name="text">
     <string>TEMP</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_4">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>110</y>
      <width>171</width>
      <height>21</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>10</pointsize>
      <italic>true</italic>
      <underline>false</underline>
      <strikeout>false</strikeout>
     </font>
    </property>
    <property name="cursor">
     <cursorShape>BlankCursor</cursorShape>
    </property>
    <property name="text">
     <string>Designed by : mm1994uestc</string>
    </property>
    <property name="alignment">
     <set>Qt::AlignCenter</set>
    </property>
   </widget>
   <widget class="QLabel" name="label_5">
    <property name="geometry">
     <rect>
      <x>0</x>
      <y>50</y>
      <width>171</width>
      <height>51</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>16</pointsize>
      <italic>true</italic>
      <underline>false</underline>
      <strikeout>false</strikeout>
     </font>
    </property>
    <property name="cursor">
     <cursorShape>BlankCursor</cursorShape>
    </property>
    <property name="text">
     <string>MySQL Control</string>
    </property>
    <property name="alignment">
     <set>Qt::AlignCenter</set>
    </property>
   </widget>
   <widget class="QLabel" name="label_6">
    <property name="geometry">
     <rect>
      <x>0</x>
      <y>0</y>
      <width>321</width>
      <height>51</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>28</pointsize>
      <italic>true</italic>
      <underline>false</underline>
      <strikeout>false</strikeout>
     </font>
    </property>
    <property name="cursor">
     <cursorShape>BlankCursor</cursorShape>
    </property>
    <property name="text">
     <string>Qt interface Demo!</string>
    </property>
    <property name="alignment">
     <set>Qt::AlignCenter</set>
    </property>
   </widget>
   <widget class="QLabel" name="label_7">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>220</y>
      <width>51</width>
      <height>31</height>
     </rect>
    </property>
    <property name="text">
     <string>Insert:</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_8">
    <property name="geometry">
     <rect>
      <x>20</x>
      <y>160</y>
      <width>51</width>
      <height>31</height>
     </rect>
    </property>
    <property name="text">
     <string>Search:</string>
    </property>
   </widget>
   <widget class="QTextEdit" name="SearchInput">
    <property name="geometry">
     <rect>
      <x>80</x>
      <y>160</y>
      <width>101</width>
      <height>31</height>
     </rect>
    </property>
   </widget>
   <widget class="QLabel" name="label_9">
    <property name="geometry">
     <rect>
      <x>100</x>
      <y>140</y>
      <width>65</width>
      <height>17</height>
     </rect>
    </property>
    <property name="text">
     <string>NAME</string>
    </property>
   </widget>
   <widget class="QPushButton" name="pushButton_2">
    <property name="geometry">
     <rect>
      <x>320</x>
      <y>160</y>
      <width>51</width>
      <height>27</height>
     </rect>
    </property>
    <property name="text">
     <string>Search</string>
    </property>
   </widget>
   <widget class="QLabel" name="SearchRes">
    <property name="geometry">
     <rect>
      <x>230</x>
      <y>160</y>
      <width>81</width>
      <height>31</height>
     </rect>
    </property>
    <property name="text">
     <string>Search Res</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_11">
    <property name="geometry">
     <rect>
      <x>180</x>
      <y>160</y>
      <width>65</width>
      <height>31</height>
     </rect>
    </property>
    <property name="font">
     <font>
      <pointsize>22</pointsize>
      <weight>75</weight>
      <bold>true</bold>
     </font>
    </property>
    <property name="text">
     <string>---&gt;</string>
    </property>
   </widget>
   <widget class="QLabel" name="label_10">
    <property name="geometry">
     <rect>
      <x>220</x>
      <y>50</y>
      <width>110</width>
      <height>110</height>
     </rect>
    </property>
    <property name="text">
     <string>              Cover</string>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>400</width>
     <height>25</height>
    </rect>
   </property>
  </widget>
  <widget class="QToolBar" name="mainToolBar">
   <attribute name="toolBarArea">
    <enum>TopToolBarArea</enum>
   </attribute>
   <attribute name="toolBarBreak">
    <bool>false</bool>
   </attribute>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

界面的设计如右图所示

我们能够分析功能，在search中填入内容之后，点击search按钮就会根据程序中定义使用的mysql数据库的数据库以及表进行数据的查询工作，并将查询的结果输出到右侧的lable当中。

Step2：根据上述分析的MySQ_UI的功能设计，完成槽函数的定义和实现：

首先需要添加sql的核心模块（关于sql模块的安装参考我的另一篇博客：http://www.cnblogs.com/uestc-mm/p/8920525.html）：

QT += core gui sql

下面首先是mainwindow.h文件的内容，包含了头文件：#include <QSqlDatabase>、#include <QSqlQuery>这两个MySQL数据库需要使用到的头文件；

声明定义了SLOT槽函数：void on_pushButton_clicked(bool checked)、void on_pushButton_2_clicked()

定义了私有成员变量db：  QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL")

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QSqlDatabase>
#include <QDebug>
#include <QSqlQuery>

namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
private slots:
    void on_pushButton_clicked(bool checked);
    void on_pushButton_2_clicked();
private:
    Ui::MainWindow *ui;
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL"); // define the db via
};
#endif // MAINWINDOW_H

接着在mainwindow.cpp文件中对变量db进行初始化和MySQL数据库进行连接， 并实现对应的槽函数：

void MainWindow::on_pushButton_clicked(bool checked)
{
    QString ID,NAME,TEMP;
    ID = ui->textEdit->toPlainText(); // Get the input content
    NAME = ui->textEdit_2->toPlainText();
    TEMP = ui->textEdit_3->toPlainText();
    qDebug() << "ID:" << ID << "  " << "NAME:" << NAME << "  " << "TEMP:" << TEMP;

    qDebug() << "Aviliable SQL drivers!";
    QStringList drivers = QSqlDatabase::drivers(); //Getting the support databases,if do not have the database driver,we can not use this databse
    foreach(QString driver,drivers)
        qDebug() << driver;

    if(!db.open()) // Connect to the database
    {
        qDebug() << "failed to connect to the mysql database!";
    }
    else
    {
        qDebug() << "Mysql is successfully Opened!";
    }

    QSqlQuery query(db); //Create a new query for db,use query to change the content

    QString Command_insert[] = {"insert into ","GanSu","BeiJing"," values(",")"};
    QString Command = "";
    Command = Command_insert[]+Command_insert[]+Command_insert[]+ID+","+"\""+NAME+"\""+","+TEMP+Command_insert[]; // Combine the command

    qDebug() << Command;

    query.exec(Command); // excute the command to control the database
}

void MainWindow::on_pushButton_2_clicked()
{
    if(!db.open())
    {
        qDebug() << "failed to connect to the mysql database!";
    }
    else
    {
        qDebug() << "Mysql is successfully Opened!";
    }

    QSqlQuery query(db);
    QString name,command;
    QString Command_search[] = {"select * from GanSu where name=","'"};

    name = ui->SearchInput->toPlainText();
    qDebug() << name;
    command = Command_search[] + Command_search[] + name + Command_search[];

    qDebug() << command;

    query.exec(command);

    while(query.next()) // wait for database finish the command just now
    {
        int val1 = query.value().toInt();
        QString val2 = query.value().toString(); // Getting the content in the query!
        int val3 = query.value().toInt();
        qDebug() << val1 << val2 << val3;

        ui->SearchRes->setText(query.value().toString()+query.value().toString()+query.value().toString());
    }
}

完成上述操作就可以编译运行Qt程序了。