PySide.QtGui.QMenu class provides a menu widget for use in menu bars, context menus, and other popup menus.
菜单 Widget 是选择菜单。它可以是菜单栏中的下拉菜单，或独立上下文菜单。下拉菜单通过菜单栏展示当用户点击各项或按下指定快捷键时。使用 QMenuBar.addMenu() to insert a menu into a menu bar. Context menus are usually invoked by some special keyboard key or by right-clicking. They can be executed either asynchronously with PySide.QtGui.QMenu.popup() or synchronously with exec() . Menus can also be invoked in response to button presses; these are just like context menus except for how they are invoked.
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Fig. A menu shown in Plastique widget style , Windows XP widget style ，和 Macintosh widget style .
A menu consists of a list of action items. Actions are added with the PySide.QtGui.QMenu.addAction() , PySide.QtGui.QWidget.addActions() and PySide.QtGui.QWidget.insertAction() functions. An action is represented vertically and rendered by PySide.QtGui.QStyle . In addition, actions can have a text label, an optional icon drawn on the very left side, and shortcut key sequence such as “Ctrl+X”.
The existing actions held by a menu can be found with PySide.QtGui.QWidget.actions() .
There are four kinds of action items: separators, actions that show a submenu, widgets, and actions that perform an action. Separators are inserted with PySide.QtGui.QMenu.addSeparator() , submenus with PySide.QtGui.QMenu.addMenu() , and all other items are considered action items.
When inserting action items you usually specify a receiver and a slot. The receiver will be notifed whenever the item is PySide.QtGui.QAction.triggered() . In addition, PySide.QtGui.QMenu provides two signals, activated() and highlighted() , which signal the PySide.QtGui.QAction that was triggered from the menu.
清零菜单采用 PySide.QtGui.QMenu.clear() and remove individual action items with PySide.QtGui.QWidget.removeAction() .
A PySide.QtGui.QMenu can also provide a tear-off menu. A tear-off menu is a top-level window that contains a copy of the menu. This makes it possible for the user to “tear off” frequently used menus and position them in a convenient place on the screen. If you want this functionality for a particular menu, insert a tear-off handle with PySide.QtGui.QMenu.setTearOffEnabled() . When using tear-off menus, bear in mind that the concept isn't typically used on Microsoft Windows so some users may not be familiar with it. Consider using a PySide.QtGui.QToolBar 代替。
Widgets can be inserted into menus with the PySide.QtGui.QWidgetAction class. Instances of this class are used to hold widgets, and are inserted into menus with the PySide.QtGui.QMenu.addAction() overload that takes a PySide.QtGui.QAction .
Conversely, actions can be added to widgets with the PySide.QtGui.QMenu.addAction() , PySide.QtGui.QWidget.addActions() and PySide.QtGui.QWidget.insertAction() 函数。
警告
To make PySide.QtGui.QMenu visible on the screen, exec() or PySide.QtGui.QMenu.popup() should be used instead of PySide.QtGui.QWidget.show() .
