如果QMainWindow处于隐藏状态，则关闭对话框退出应用程序

QMainWindow* mainWindow = new QMainWindow();

mainWindow->hide();

QObject::connect(mainWindow, &QMainWindow::destroyed, QCoreApplication::quit);

QApplication app(argc, argv);
int result = app.exec();

#include <QApplication>
#include <QMainWindow>

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

    QMainWindow* mainWindow = new QMainWindow();
    mainWindow->hide();

    QObject::connect(mainWindow, &QMainWindow::destroyed, QCoreApplication::quit);

    int result = app.exec();

    delete mainWindow;

    return result;
}