如何在QT中打开子界面窗口时关闭父界面窗口

void ParentWindow::openChildWindow()
{
    ChildWindow* childWindow = new ChildWindow();
    childWindow->show();
    this->close();
}

void ChildWindow::closeEvent(QCloseEvent* event)
{
    ParentWindow* parentWindow = new ParentWindow();
    parentWindow->show();
    event->accept();
}

void MainWindow::on_openChildWindowButton_clicked()
{
    ParentWindow* parentWindow = new ParentWindow();
    connect(parentWindow, SIGNAL(openChildWindow()), this, SLOT(openChildWindow()));
    parentWindow->show();
}