private:
    QMenu* fileMenu;
    QMenu* recentFilesMenu;

    QAction* openAction;
    QList<QAction*> recentFileActionList;
    const int maxFileNr=5;

    QString currentFilePath;
    QLabel *imageLabel;

    void loadFile(const QString& filePath);
    void adjustForCurrentFile(const QString& filePath);
    void updateRecentActionList();

    imageLabel = new QLabel;
    setCentralWidget(imageLabel);//設(shè)置中心部件
    //Open Action
    openAction = new QAction(tr("&Open..."), this);//open
    openAction->setShortcuts(QKeySequence::Open);  //設(shè)置快捷鍵
    connect(openAction, &QAction::triggered, this, [=]()
    {
        QString filePath = QFileDialog::getOpenFileName(
                           this, tr("Open File"), "",
                           tr("Images (*.png *.xpm *.jpg *.gif)"));
        if (!filePath.isEmpty())
            loadFile(filePath);
    });

    //recentFile Action
    QAction* recentFileAction = nullptr;
    for(auto i = 0; i < maxFileNr; ++i){
        recentFileAction = new QAction(this);
        recentFileAction->setVisible(false);

        connect(recentFileAction, &QAction::triggered, this, [=]()
        {
            loadFile(recentFileAction->data().toString());
        });
        recentFileActionList.append(recentFileAction);
    }

    // create menus
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(openAction);

    recentFilesMenu = fileMenu->addMenu(tr("Open Recent"));
    for(auto i = 0; i < maxFileNr; ++i)
        recentFilesMenu->addAction(recentFileActionList.at(i));

    updateRecentActionList();

    resize(350, 250);//調(diào)整尺寸

//加載圖片
void MainWindow::loadFile(const QString &filePath){
    QFile file(filePath);
    //如果不能打開
    if (!file.open(QFile::ReadOnly)) {
        QMessageBox::warning(this, tr("Recent Photos"),
                             tr("This file could not be found:\n%1.")
                             .arg(filePath));
        return;
    }

    QPixmap pMap(filePath);
    //如果圖片為空
    if (pMap.isNull()) {
        QMessageBox::information(this, tr("Recent Photos"),
                      tr("Cannot load:\n%1.")
                      .arg(filePath));
        return;
    }

    imageLabel->setPixmap(pMap);                //顯示圖像
    imageLabel->setAlignment(Qt::AlignCenter);  //居中對(duì)齊
    adjustForCurrentFile(filePath);
}

//調(diào)整當(dāng)前文件(使得每次新打開的文件都在最上方)
void MainWindow::adjustForCurrentFile(const QString &filePath){
    currentFilePath = filePath;
    setWindowFilePath(currentFilePath);


    QSettings settings("Recently", "Recent Photos");
    QStringList recentFilePaths = settings.value("recentPhotos").toStringList();//獲取鍵對(duì)應(yīng)的值
    recentFilePaths.removeAll(filePath);    //移除filePath
    recentFilePaths.prepend(filePath);      //在開頭增加filePath
    //如果尺寸超過最大尺寸，則刪除最后一項(xiàng)
    while (recentFilePaths.size() > maxFileNr)
        recentFilePaths.removeLast();
    settings.setValue("recentPhotos", recentFilePaths);//設(shè)置鍵recentPhotos對(duì)應(yīng)的值

    updateRecentActionList();
}

//更新recentFileActionList
void MainWindow::updateRecentActionList(){
    QSettings settings("Recently", "Recent Photos");
    QStringList recentFilePaths = settings.value("recentPhotos").toStringList();//獲取鍵對(duì)應(yīng)的值

    auto itEnd = 0;
    if(recentFilePaths.size() <= maxFileNr)
        itEnd = recentFilePaths.size();
    else
        itEnd = maxFileNr;

    for (auto i = 0; i < itEnd; ++i) {
        QString strippedName = QFileInfo(recentFilePaths.at(i)).fileName();//返回文件名(不包含路徑)
        recentFileActionList.at(i)->setText(strippedName);  //描述性文本
        recentFileActionList.at(i)->setData(recentFilePaths.at(i)); //數(shù)據(jù)
        recentFileActionList.at(i)->setVisible(true);
    }

    for (auto i = itEnd; i < maxFileNr; ++i)
        recentFileActionList.at(i)->setVisible(false);
}