1、初始化界面

QPixmap pixmap(":/Pim/123.jpg");
QSplashScreen splash(pixmap);
splash.show();
{
  //初始化
  for(long i=1;i<1000000000;i++);
}
 splash.finish(&w);//QSplashScreen::finish(QWidget *mainWin)；

2、共享内存，图片

void MainWindow::on_pushButton_5_clicked()
{
    QString fileName = QFileDialog::getOpenFileName(0, QString(), QString(),
                                       tr("Images (*.png *.xpm *.jpg)"));
    QImage image;
       if (!image.load(fileName)) {
            qDebug()<<"Selected file is not an image, please select another.";
            return;
       }
       ui->label->setPixmap(QPixmap::fromImage(image));//
       QBuffer buffer;
       buffer.open(QBuffer::ReadWrite);
       QDataStream out(&buffer);
       out << image;//
       int size = buffer.size();
        sharedMemory= new QSharedMemory("memoryKey");//需要传入keyName,才可以
       if(sharedMemory->isAttached()) {
             if(!sharedMemory->detach()) {
                 QMessageBox::information(this, tr("错误"), tr("共享内存失败释放"), QMessageBox::Yes);
                 return;
             }
         }
       //sharedMemory.setKey("memoryKey"); //更换关键字
       if(!sharedMemory->create(buffer.size())) {
              QMessageBox::information(this, tr("创建共享内存失败"), tr(sharedMemory->errorString().toLatin1().data()), QMessageBox::Yes);
              return;
          }
//        QSharedMemory sharedMemory;
        sharedMemory->lock();
        char *to = (char*)sharedMemory->data();
        const char *from = buffer.data().data();
        memcpy(to, from, qMin(sharedMemory->size(), size));
        sharedMemory->unlock();

}

void MainWindow::on_pushButton_6_clicked()
{
    sharedMemory= new QSharedMemory("memoryKey");//需要传入keyName,才可以
    if(!sharedMemory->attach()){
                QMessageBox::information(this, tr("错误"), tr("共享内存打开失败"), QMessageBox::Yes);
                return;
            }
        QBuffer buffer;
        QDataStream in(&buffer);
        QImage  image;

        sharedMemory->lock();
        buffer.setData((char*)sharedMemory->constData(), sharedMemory->size());
        buffer.open(QBuffer::ReadOnly);
        in >> image;//read
        sharedMemory->unlock();
        sharedMemory->detach();

    ui->label->setPixmap(QPixmap::fromImage(image));
}

3、鼠标位置

#include<QPushButton>
#include<QMouseEvent>

this->setMouseTracking(true);//MainWindow

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    event->ignore();
    if ((windowType() != Qt::Widget)) {
        event->accept();
        QWidget* w;
        while ((w = QApplication::activePopupWidget()) && w != this){
            w->close();
            if (QApplication::activePopupWidget() == w)
            w->hide(); // hide at least
        }
        if (!rect().contains(event->pos())){
            close();
        }
    }
        ui->label_3->setText(QString("<center><h1>Move: (%1, %2)</h1></center>").arg(QString::number(event->x()),QString::number(event->y())));
}

void MainWindow::mousePressEvent(QMouseEvent *event)
{
    ui->label_4->setText(QString("<center><h1>Press: (%1, %2)</h1></center>").arg(QString::number(event->x()),QString::number(event->y())));
}

void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    QString msg;
    msg.sprintf("<center><h1>Release: (%d, %d)</h1></center>",event->x(), event->y());
    ui->label_5->setText(msg);
}

4、截图视频

录视频
//void MainWindow::on_pushButton_1_clicked()
//{
//    if(ui->checkBox->isChecked())
//    {
        this->hide();
//        this->timerp=new QTimer;
//        connect(this->timerp,&QTimer::timeout,this,&MainWindow::shotScreenSlot);
//        this->timerp->start(1000/24);
//    }
//    else{
//        qApp->beep();
//    }
//}

//void MainWindow::shotScreenSlot()
//{
//    pixmapp= QPixmap::grabWindow(QApplication::desktop()->winId());

//    ui->label->setPixmap(this->pixmapp.scaled(ui->label->size()));
    this->show();
//    //    this->timerp->stop();
//}

//截图
void MainWindow::on_pushButton_1_clicked()
{
    if(ui->checkBox->isChecked())
    {
        this->hide();
        this->timerp=new QTimer;
        connect(this->timerp,&QTimer::timeout,this,&MainWindow::shotScreenSlot);
        this->timerp->start(ui->spinBox->value()*1000);
    }
    else{
        qApp->beep();
    }
}

#include<QDebug>
#include<QClipboard>
void MainWindow::shotScreenSlot()
{
    pixmapp= QPixmap::grabWindow(QApplication::desktop()->winId());

    QClipboard *clipboard = QGuiApplication::clipboard();
//    QString originalText = clipboard->text();
//    qDebug()<<originalText;
//     clipboard->setImage(this->pixmapp);

    ui->label->setPixmap(this->pixmapp.scaled(ui->label->size()));
    this->show();
    this->timerp->stop();//QTimer *timerp;
}

5.sqlit、mysql

//smysql
    db=QSqlDatabase::addDatabase("QMYSQL");//QSQLITE
    db.setHostName("localhost");
    db.setPort(3306);
    db.setUserName("root");
    db.setPassword("smts");
    db.setDatabaseName("student");
    if(!db.open( ))
      qDebug()<<"错误："<<db.lastError();
     else
        qDebug()<<"成功："<<db.lastError();

/*
//qsqlite   #include<QVariant>
    db=QSqlDatabase::addDatabase("QSQLITE");//QSQLITE
    db.setDatabaseName("studb.db");
//    db.setUserName("staff");
    if(!db.open( ))
      qDebug()<<"错误："<<db.lastError();
     else
        qDebug()<<"成功";

     QSqlQuery query;
     query.prepare("INSERT INTO staff (id, name, age) "
                         "VALUES (:id, :name, :age)");
           query.bindValue(":id", 1001);
           query.bindValue(":name", "Bart");
           query.bindValue(":age", "Simpson");
           query.exec();

     QString select_all_sql = "select * from staff";
     query.prepare(select_all_sql);
     if(!query.exec())
     {
         qDebug()<<query.lastError();
     }
     else
     {
         while(query.next())
         {
             int id = query.value(0).toInt();
             QString name = query.value(1).toString();
             int age = query.value(2).toInt();
             qDebug()<<QString("id:%1    name:%2    age:%3").arg(id).arg(name).arg(age);
         }
     }

*/
//     QList<QVariant> list = query.boundValues().values();
//         for (int i = 0; i < list.size(); ++i)
//            qDebug() << i << ": " << list.at(i).toString().toUtf8().data() << endl;
//     while(query.next())
//     {
//         int rowid=query.value(0).toUInt();
//         QString nameSqlite=query.value(1).toString();
//         int age=query.value(2).toInt();
//         qDebug()<<rowid<<"  "<<nameSqlite<<"  "<<age;
//     }

//    QSqlQuery query3;
//    QString sqlcreate=QString("create table staff(id integer primary key autoincrement,"
//                              "name varchar(20),"
//                              "age int);");
//         qDebug()<<query3.exec(sqlcreate);


//    QString sqlcreate2=QString("insert into staff(name,age) values('助手1',20);");
//     if(!query3.exec(sqlcreate2))
//     {
//         qDebug()<<query3.exec(sqlcreate2)<<db.lastError();
//     }

//     QString sqlcreate3=QString("select * from staff;");

//      if(!query3.exec(sqlcreate3))
//      {
//          qDebug()<<query3.exec(sqlcreate3)<<db.lastError();
//      }

//      while(query3.next())
//       {
//          qDebug()<<query3.value("name").toString();
//           qDebug()<<query3.value("age").toInt();
//      }

//      QString sqldelete=QString("delete from staff where id=4");
//      if(!query3.exec(sqldelete))
//      {
//          qDebug()<<"delete data error"<<db.lastError();
//      }

//      sqldelete=QString("update staff set name = '历史' where id=3");
//            if(!query3.exec(sqldelete))
//            {
//                qDebug()<<"delete data error"<<db.lastError();
//            }

//      sqlcreate3=QString("select * from staff;");
//            if(!query3.exec(sqlcreate3))
//            {
//                qDebug()<<query3.exec(sqlcreate3)<<db.lastError();
//            }

//            while(query3.next())
//             {
//                qDebug()<<query3.value("name").toString();
//                 qDebug()<<query3.value("age").toInt();
//            }

//     QString sqlcreate=QString("INSERT INTO Websites (name, url, alexa, country)"
//                   "VALUES ('百度','https://www.baidu.com/','4','CN')");

//    QString sqlcreate=QString("INSERT INTO staff(Name,Age,Gender)"
//                              "VALUES(:Name,:Age,:Gender)");

//    query.prepare("INSERT INTO table_name (column1,column2,column3)"
//                 "VALUES (value1,value2,value3)");

//    query.bindValue("value1","小米");
//    query.bindValue("value2","12");
//    query.bindValue("value3","13123213");
//    query.exec();

//      QSqlQuery query;
//      query.prepare("INSERT INTO person (id, forename, surname) "
//                    "VALUES (:id, :forename, :surname)");
//      query.bindValue(":id", 1001);
//      query.bindValue(":forename", "Bart");
//      query.bindValue(":surname", "Simpson");
//      qDebug()<<query.exec();

//      QSqlQuery query2;
//      query2.exec("INSERT INTO employee (id, name, salary) "
//                       "VALUES (1001, 'Thad Beaumont', 65000)");
//      qDebug()<<query2.exec();

//    connect(ui->actionbug_H,&QAction::triggered,this,&MainWindow::close)
}