通过Qt TCP套接字更改Qt GUI？

Question

我有一个服务器和client.i将时钟的句柄更改为新值，该值将由client发送到server.i在下面添加了源代码。 我的问题是当客户端向服务器发送数据以将时钟的句柄更改为新数据后，客户端连接到服务器。 在Server :: startRead（）方法中创建的gui会自动出现和消失 。 请问我的代码有什么问题。

服务器

#ifndef SERVER_H
#define SERVER_H
#include <QtNetwork>
#include <QObject>
#include <QTcpServer>
#include <QTcpSocket>

class Server: public QObject
{
Q_OBJECT
public:

   QString buf;
  Server(QObject * parent = 0);
  ~Server();
public slots:
  void acceptConnection();
  void startRead();
  QString getinfo();

private:
  QTcpServer server;
  QTcpSocket* client;
};


#endif // SERVER_H

server.cpp

#include <QGuiApplication>
#include "server.h"
#include <QDebug>
#include <iostream>
#include <QApplication>
#include "qlabel.h"
#include <QtGui>
Server::Server(QObject* parent): QObject(parent)
{

connect(&server, SIGNAL(newConnection()),
    this, SLOT(acceptConnection()));


  server.listen(QHostAddress::Any, 1234);
  qDebug() <<  "connected";
}

Server::~Server()
{
  server.close();
}

void Server::acceptConnection()
{

  qDebug()<<"accept connection";
  client = server.nextPendingConnection();
  client->write("Hello client\r\n");

  connect(client, SIGNAL(readyRead()),
    this, SLOT(startRead()));

}

void Server::startRead()
{

    client->waitForReadyRead(3000);
    QString buf=client->readAll();

    qDebug() << buf;

    static const QPoint minuteHand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -40)
    };
     int side = qMin(200, 200);
    QColor minuteColor(60, 60, 0);
    QPixmap pixmap( 200, 200 );
    pixmap.fill( Qt::red );
    QPainter painter( &pixmap );
    painter.setRenderHint(QPainter::Antialiasing);
    painter.translate(200 / 2, 200 / 2);
    painter.scale(side / 200.0, side / 200.0);

    painter.setPen(Qt::NoPen);

    for (int i = 0; i < 12; ++i) {
        painter.drawLine(88, 0, 96, 0);
        painter.rotate(30.0);
    }
    painter.setPen(Qt::NoPen);
    painter.setBrush(minuteColor);

    painter.save();
    painter.rotate(240);
    painter.drawConvexPolygon(minuteHand, 3);
    painter.restore();

    painter.setPen(minuteColor);

    for (int j = 0; j < 60; ++j) {
        if ((j % 5) != 0)
            painter.drawLine(92, 0, 96, 0);
        painter.rotate(6.0);
    }

    QLabel l;
    l.setPixmap(pixmap);
    l.show();

}
QString Server::getinfo()
{

 qDebug()<< buf;
    return buf;

}

main.cpp

#include "server.h"
#include <QApplication>
#include "analogclock.h"
#include "qlabel.h"
#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

Server s;



    return a.exec();
}

应用程序输出

Starting C:\Qt\Qt5.3.0_1\Tools\QtCreator\bin\build-NHAJA-Desktop_Qt_5_3_0_MinGW_32bit-Debug\debug\NHAJA.exe...
connected
accept connection
"11"
C:\Qt\Qt5.3.0_1\Tools\QtCreator\bin\build-NHAJA-Desktop_Qt_5_3_0_MinGW_32bit-Debug\debug\NHAJA.exe exited with code 0

我真的很感激。

Answer 1

在函数中创建的变量仅在调用函数时存在，因此在函数执行完毕后，将消除变量，在您的情况下，将消除QLabel。

一个可能的解决方案是将QLabel创建为该类的成员：

服务器

private:
    QLabel *label;

server.cpp

Server::Server(QObject *parent) : QObject(parent)
{
    [...]
    qDebug() <<  "connected";
    label = new QLabel;
}

void Server::startRead()
{
    [...]
    for (int j = 0; j < 60; ++j) {
        if ((j % 5) != 0)
            painter.drawLine(92, 0, 96, 0);
        painter.rotate(6.0);
    }

    label->setPixmap(pixmap);
    label->show();

}