QTConcurrent多次触发信号

Question

我正在编写一个c++ qt程序。所以我有两节课。在mainwindow中，我有一个函数，该函数在单击按钮时触发，并在另一个线程上运行第二个类中的函数。当我第一次调用这个函数时，一切正常，但是当我第二次运行这个函数时，这个函数已经被调用了两次等等。

这是我的代码: mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "secondclass.h"

#include <QFutureWatcher>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

public slots:
    void slot(QString text);
private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
    secondClass* secondclass;
    QFutureWatcher<void>* futureWatcher;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QFuture>
#include <QFutureWatcher>
#include <QtConcurrent/QtConcurrent>
#include <iostream>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , secondclass(new secondClass())
{
    ui->setupUi(this);
    connect(secondclass, &secondClass::signal, this, &MainWindow::slot);
}

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


void MainWindow::on_pushButton_clicked()
{
    auto futureWatcher = new QFutureWatcher<void>(this);
    connect(futureWatcher, &QFutureWatcher<void>::finished, futureWatcher, &QFutureWatcher<void>::deleteLater);
    futureWatcher->setFuture(QtConcurrent::run( [=]{ secondclass->func();}));
}

void MainWindow::slot(QString text)
{
    std::cout << text.toStdString() << std::endl;
}

secondclass.h

#ifndef SECONDCLASS_H
#define SECONDCLASS_H

#include <QObject>

class secondClass : public QObject
{
    Q_OBJECT
public:
    secondClass();
    void func();

signals:
    void signal(QString text);
};

#endif // SECONDCLASS_H

secondclass.cpp

#include "secondclass.h"
#include <QString>
#include <sstream>
#include <iostream>

secondClass::secondClass()
{
}

QString text;
std::ostringstream ss;

void secondClass::func()
{
    text.clear();
    ss << "Test\n";
    std::cout << "Test thread" << std::endl;
    text = QString::fromStdString(ss.str());
    signal(text);
}

Answer 1

您应该只调用QObject::connect(...)一次，每次输入on_pushButton_3_clicked()时，您都要创建另一个连接。将connect调用移动到MainWindow构造函数，或者移到只发生一次的其他地方。