![[Pasted image 20220519094358.png]]

1. Button必須是QToolButton.
2. 建立menu.
3. 建立action.
4. 把action加到menu裡面
5. 把menu設定給button
6. code example:
    ```cpp
    QMenu* saveFrameMenu = new QMenu;
    saveRawAction = new QAction(QIcon(QPixmap(":/image/resources/button-raw.png")), "SaveRaw", this);
    saveJpgAction = new QAction(QIcon(QPixmap(":/image/resources/button-jpg.png")), "SaveJpg", this);
    saveBmpAction = new QAction(QIcon(QPixmap(":/image/resources/button-bmp.png")), "SaveBmp", this);
    saveFrameMenu->addAction(saveRawAction);
    saveFrameMenu->addAction(saveJpgAction);
    saveFrameMenu->addAction(saveBmpAction);
    ui.toolButtonSaveFrame->setMenu(saveFrameMenu);
    ui.toolButtonSaveFrame->setDefaultAction(saveJpgAction);
    ui.toolButtonSaveFrame->setToolButtonStyle(Qt::ToolButtonTextBesideIcon);
    ui.toolButtonSaveFrame->setPopupMode(QToolButton::MenuButtonPopup);
    ```