Qt 用代码实现菜单栏(MenuBar)和工具栏(ToolBar)

新建Qt项目，选择Qt Widgets Application，填入项目名称“ImageView”，点击完成。

在Qt Designer里会生成如图所示的几个文件：

此时我们右键删除imageviewer.ui这个文件，因为我们本次是用纯代码的方式生成界面，所以不需要这个ui文件了。

关键代码主要在imageviewer.h和imageviewer.cpp里。下面是代码：

imageviewer.h

#ifndef IMAGEVIEWER_H
#define IMAGEVIEWER_H

#include <QMainWindow>
#include <QLabel>
#include <QScrollArea>
#include <QMenu>
#include <QMenuBar>
#include <QToolBar>

namespace Ui {
class ImageViewer;
}

class ImageViewer : public QMainWindow
{
    Q_OBJECT

public:
    explicit ImageViewer(QWidget *parent = nullptr);
    ~ImageViewer();

    void initMenu();
    void initToolBar();
    void initConnect();

private:
    Ui::ImageViewer *ui;
    QLabel *imageLabel;
    QScrollArea *scrollAera;

    QMenu *fileMenu;
    QMenu *viewMenu;
    QMenu *helpMenu;

    QToolBar *fileToolBar;

    QAction *openAct;
    QAction *printAct;
    QAction *exitAct;
    QAction *zoomInAct;
    QAction *zoomOutAct;
    QAction *normalSizeAct;
    QAction *fitToWindowAct;
    QAction *aboutAct;
    QAction *aboutQtAct;

private slots:
    void open();
    void print();
    void exit();
    void zoomIn();
    void zoomOut();
    void normalSize();
    void fitToWindow();
    void about();
    void aboutQt();
};

#endif // IMAGEVIEWER_H

imageviewer.cpp

#include "imageviewer.h"
#include "ui_imageviewer.h"

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

    //initalize
    initMenu();
    initToolBar();
    initConnect();
}

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

void ImageViewer::initMenu()
{
    //QMenuBar *menuBar = this->menuBar();
    //add three menus
    fileMenu = new QMenu(tr("&File"),this);
    viewMenu = new QMenu(tr("&View"),this);
    helpMenu = new QMenu(tr("&About"),this);

    //add actions and add it into corresponding menu
    openAct = new QAction(tr("&Open"),this);
    openAct -> setShortcut(tr("ctrl+O"));
    printAct = new QAction(tr("&Print"),this);
    printAct -> setShortcut(tr("ctrl+P"));
    exitAct = new QAction(tr("&Exit"),this);
    exitAct -> setShortcut(tr("ctrl+Q"));
    fileMenu -> addAction(openAct);
    fileMenu -> addAction(printAct);
    fileMenu -> addSeparator();
    fileMenu -> addAction(exitAct);

    zoomInAct = new QAction(tr("Zoom &In"),this);
    zoomInAct -> setShortcut(tr("ctrl+="));
    zoomOutAct = new QAction(tr("Zoom &Out"),this);
    zoomOutAct -> setShortcut(tr("ctrl+-"));
    normalSizeAct = new QAction(tr("&Normal Size"),this);
    normalSizeAct -> setShortcut(tr("ctrl+S"));
    fitToWindowAct = new QAction(tr("&Fit to Window"),this);
    fitToWindowAct -> setShortcut(tr("ctrl+F"));
    viewMenu -> addAction(zoomInAct);
    viewMenu -> addAction(zoomOutAct);
    viewMenu -> addAction(normalSizeAct);
    viewMenu -> addSeparator();
    viewMenu -> addAction(fitToWindowAct);

    aboutAct = new QAction(tr("&About"),this);
    aboutQtAct = new QAction(tr("&About Qt"),this);
    helpMenu -> addAction(aboutAct);
    helpMenu -> addAction(aboutQtAct);

    //add menus to menubar
    menuBar() -> addMenu(fileMenu);
    menuBar() -> addMenu(viewMenu);
    menuBar() -> addMenu(helpMenu);
}

void ImageViewer::initToolBar()
{
    //add a toolbar and add its actions
     fileToolBar = new QToolBar(this);

     fileToolBar -> addAction(openAct);
     fileToolBar -> addAction(printAct);
     fileToolBar -> addAction(exitAct);

     addToolBar(Qt::TopToolBarArea,fileToolBar);
}

void ImageViewer::initConnect()
{
    //singals and slots
    connect(openAct,SIGNAL(triggered),this,SLOT(open()));
    connect(printAct,SIGNAL(triggered),this,SLOT(print()));
    connect(exitAct,SIGNAL(triggered),this,SLOT(exit()));
    connect(zoomInAct,SIGNAL(triggered),this,SLOT(zoomIn()));
    connect(zoomOutAct,SIGNAL(triggered),this,SLOT(zoomOut()));
    connect(normalSizeAct,SIGNAL(triggered),this,SLOT(normalSize()));
    connect(fitToWindowAct,SIGNAL(triggered),this,SLOT(fitToWindow()));
    connect(aboutAct,SIGNAL(triggered),this,SLOT(about()));
    connect(aboutQtAct,SIGNAL(triggered),this,SLOT(aboutQt()));
}

//implement slot functions
void ImageViewer::open()
{

}

void ImageViewer::print()
{

}

void ImageViewer::exit()
{

}

void ImageViewer::zoomIn()
{

}

void ImageViewer::zoomOut()
{

}

void ImageViewer::normalSize()
{

}

void ImageViewer::fitToWindow()
{

}

void ImageViewer::about()
{

}

void ImageViewer::aboutQt()
{

}

界面效果如图：