QT5.14用代码创建菜单和子菜单

　　　　　//添加菜单栏
        QMenuBar *menuBar;
        menuBar = new QMenuBar(this);
        this->setMenuBar(menuBar);

        //1.给菜单栏添加标准文件菜单
        QMenu *menuFile;
        menuFile = new QMenu(menuBar);
        menuBar->addAction(menuFile->menuAction());
        //设置文本和快捷键, 通常导航栏中&F指Alt+F, 菜单中&O指Ctrl+O
        menuFile->setTitle(tr("File(&F)"));

        //2.创建子菜单并添加信号槽
        QAction *actionOpen;
        actionOpen = new QAction(this);
        actionOpen->setStatusTip(tr("Open an existing file"));      //设置状态栏提示, 鼠标悬浮时状态栏会提示对应信息
        connect(actionOpen, &QAction::triggered, this, &MainWindow::open);      //关联槽函数

        QAction *actionSave;
        actionSave = new QAction(this);
　　　　 //3.给文件菜单添加子菜单
        menuFile->addAction(actionOpen);
        menuFile->addSeparator();//给菜单加分隔条
        menuFile->addAction(actionSave);

        //给Open和Save菜单设置文本和快捷键
        actionOpen->setText(tr("Open(&O)"));
        actionSave->setText(tr("Save(&S)"));