QT 使用 SIGNAL 和 SLOT 改变 GUI

Question

我有一个关于开发 QT 应用程序的问题。我想使用 SINGAL 和 SLOT 更改 GUI。从 mythread.cpp 的 sendValue() 到 myserver.cpp 的 showValue() 运行良好。连接非常好，我可以检查值。

但是从 myserver.cpp 到 application.cpp 的 showApp() 的 sendApp() 无法正常工作。我很困惑没有连接或没有发射或其他问题。有两个问题。一个是如何使用 SIGNAL 和 SLOT 从 sendApp() 连接到 showApp()。 emit 不行？或连接不工作？我找不到原因。另一个是如果 showApp() 函数工作是否可能？请回答我。第一次开发QT应用，非常抱歉。

application.h

#ifndef APPLICATION_H
#define APPLICATION_H

#include <QWidget>
#include <QObject>
#include <menu.h>
#include <QTcpServer>
#include "myserver.h"
#include "mythread.h"

QT_BEGIN_NAMESPACE
namespace Ui { class application; }
QT_END_NAMESPACE

class application : public QWidget
{
    Q_OBJECT

public:
    application(QWidget *parent = nullptr);
    ~application();

private slots:
    void on_menuBt_clicked();
    void menuBackBtClicked();
    void showApp(QString strValue);

private:
    Ui::application *ui;
    menu menuPage;

};

#endif // APPLICATION_H

application.cpp

#include "application.h"
#include "ui_application.h"
#include "myserver.h"
#include "mythread.h"

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

    Myserver *myserver = new Myserver(this);


    ui->firstToggle->setVisible(false);
    ui->secondToggle->setVisible(false);
    ui->thirdToggle->setVisible(false);
    ui->forthToggle->setVisible(false);
    ui->stackedWidget->addWidget(&menuPage);

    ui->stackedWidget->insertWidget(1, &menuPage);

    connect(&menuPage, SIGNAL(menuBackClick()), this, SLOT(menuBackBtClicked()));
    connect(myserver, SIGNAL(sendApp(QString)), this, SLOT(showApp(QString)));

    setWindowFlags(Qt::FramelessWindowHint);

}

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


void application::on_menuBt_clicked()
{
    ui->stackedWidget->setCurrentIndex(1); //menuLayout
}

void application::menuBackBtClicked()
{
    ui->stackedWidget->setCurrentIndex(0);
}

void application::showApp(QString strValue) {
    QString compare = "13";
    int x = QString::compare(strValue,compare, Qt::CaseInsensitive);
    if(x == 0) {
        ui->firstToggle->setVisible(true);
    }
}

myserver.h

#ifndef MYSERVER_H
#define MYSERVER_H

#include <QObject>
#include <QTcpServer>
#include "mythread.h"
#include "application.h"

class Myserver : public QTcpServer
{
    Q_OBJECT

public:
    explicit Myserver(QObject *parent = 0);
    void startServer();
signals:
    void sendApp(QString strValue);

private slots:
    void showValue(QString strValue);

protected:
    void incomingConnection(qintptr socketDescriptor);

private:
    MyThread *mythread;


};

#endif // MYSERVER_H

myserver.cpp

#include "myserver.h"
#include "mythread.h"
#include "application.h"

Myserver::Myserver(QObject *parent) :
    QTcpServer(parent)
{
}

void Myserver::startServer()
{
    int port = 3333;

    if(!this->listen(QHostAddress::Any,port))
    {
        qDebug() << "Could not start server";
    }
    else
    {
        qDebug() << "Listening to port " << port << "...";
    }
}

void Myserver::incomingConnection(qintptr socketDescriptor)
{
    // We have a new connection
    qDebug() << socketDescriptor << " Connecting...";

    MyThread *thread = new MyThread(socketDescriptor, this);

    // connect signal/slot
    // once a thread is not needed, it will be beleted later
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    connect(thread, SIGNAL(sendValue(QString)), this, SLOT(showValue(QString)));

    thread->start();
}
void Myserver::showValue(QString strValue){
    emit sendApp(strValue);
}

mythread.h

#ifndef MYTHREAD_H
#define MYTHREAD_H

#include <QObject>
#include <QTcpSocket>
#include <QThread>
#include <QDebug>

class MyThread : public QThread
{
    Q_OBJECT
public:
    explicit MyThread(qintptr ID, QObject *parent = 0);
    void run();

signals:
    void error(QTcpSocket::SocketError socketerror);
    void sendValue(QString strValue);

private slots:
    void readyRead();
    void disconnected();

private:
    QTcpSocket *socket;
    qintptr socketDescriptor;

};

#endif // MYTHREAD_H

mythread.cpp

#include "mythread.h"

#include <QThread>

MyThread::MyThread(qintptr ID, QObject *parent) :
    QThread(parent)
{
    this->socketDescriptor = ID;
}

int count = 0;

void MyThread::run()
{
    // thread starts here
    qDebug() << " Thread started";

    socket = new QTcpSocket();

    // set the ID
    if(!socket->setSocketDescriptor(this->socketDescriptor))
    {
        // something's wrong, we just emit a signal
        emit error(socket->error());
        return;
    }

    // connect socket and signal
    // note - Qt::DirectConnection is used because it's multithreaded
    //        This makes the slot to be invoked immediately, when the signal is emitted.

    connect(socket, SIGNAL(readyRead()), this, SLOT(readyRead()), Qt::DirectConnection);
    connect(socket, SIGNAL(disconnected()), this, SLOT(disconnected()));

    // We'll have multiple clients, we want to know which is which
    qDebug() << socketDescriptor << "Client connected";

    QString strValue = QString::number(socketDescriptor);

    emit sendValue(strValue);

    // make this thread a loop,
    // thread will stay alive so that signal/slot to function properly
    // not dropped out in the middle when thread dies

    exec();
}

void MyThread::readyRead()
{
    // get the information
    QByteArray Data = socket->readAll();

    // will write on server side window
    qDebug() << socketDescriptor << " Data in: " << Data;

    socket->write(Data);
}

void MyThread::disconnected()
{
    qDebug() << socketDescriptor << " Disconnected";

    socket->deleteLater();
    exit(0);
}

Answer 1

您刚刚忘记启动服务器！

在 application class constructor.

中的连接后添加 startServer() 函数调用可能会起作用

connect(&menuPage, SIGNAL(menuBackClick()), this, SLOT(menuBackBtClicked()));
connect(myserver, SIGNAL(sendApp(QString)), this, SLOT(showApp(QString)));

myserver->startServer();

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