Build a menu item.
Accelerator description, for example "Ctrl+Shift+N"; empty for none.
Current checked state (only meaningful for MenuItemKind.checkable).
Whether the item can be invoked.
Command identifier. Unique within the application's menus.
Whether the item is a normal command, a separator, or checkable.
Display label, with & marking the mnemonic letter.
Fired when the item is chosen (by mouse, mnemonic, or accelerator).
One menu command.
Construct with an id (pass 0 to have one generated), a label (an & marks the keyboard mnemonic), and an optional accelerator string. Attach a handler to onClicked before appending the item to a Menu, or look the stored item up later with Menu.findItem.