如何在自定义NSView中使用NSScroller

Question

I have a custom NSView with two NSClipViews. I want to add a vertical scroller for each clipview. The snippet below shows a NSScroller, but it is not drawing any knob or buttons. Interaction is also not possible. NSScroller is a small class, so I am not sure what I am missing here.

required init?(coder: NSCoder)
{
    super.init(coder: coder)

    let width = NSScroller.scrollerWidthForControlSize(NSControlSize.RegularControlSize, scrollerStyle: NSScrollerStyle.Overlay)

    let scroller = NSScroller(frame: NSRect(x: 10, y: 10, width: width, height: 500))
    self.addSubview(scroller)
    scroller.doubleValue = 0.5
    scroller.knobProportion = 0.1
    scroller.needsLayout = true  //no effect
    scroller.needsDisplay = true //no effect
}

Answer 1

缺失的一行：

scroller.enabled = true