Objective-C偏好窗口makeKeyAndOrderFront还是showWindow?

I'm working on a new Mac App and want to open my Preferences Window, i've got 2 Nib (xib) Files, one for the main window, and one for the Preferences Window, then i've got a openPreferences Action, which shows the Preferences Window, sth. like this:I'm working on a new Mac App and want to open m