swift - NSPopUpButton在Swift Playground中变灰

在Swift操场视图控制器中，我有以下代码：

var jsonSelector = NSPopUpButton(title: "Path", target: self, action: #selector(updatePointFile))

override public func loadView() {
    let frame = CGRect(origin: CGPoint.zero, size: CGSize(width: 900, height: 600))
    let view = NSView(frame: frame)

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

运行时，最初看起来很正常：


但是，一旦单击它，它看起来像：


当您单击鼠标左键时，它将保持不可点击状态：


当我将完全相同的代码复制到完整的Mac应用程序中时，它的工作原理与正常一样，并且使事情变得更加奇怪，有一次，当我拍摄这些屏幕截图时，它可以一次选择并返回到灰色状态。

任何帮助将不胜感激。

最佳答案

因此，解决此问题的方法有点怪异。它只需要稍后定义目标即可。

这意味着

var jsonSelector = NSPopUpButton(frame: NSRect(origin: CGPoint.zero, size: CGSize(width: 100, height: 50)))

override public func loadView() {
    jsonSelector.target = self
        jsonSelector.action = #selector(updatePointFile)

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

要么

var jsonSelector = NSPopUpButton(title: "Path", target: self, action: #selector(updatePointFile))

override public func loadView() {
    let frame = CGRect(origin: CGPoint.zero, size: CGSize(width: 900, height: 600))
    let view = NSView(frame: frame)

    jsonSelector.target = self

    let array = // gets array of items
    for item in array {
        jsonSelector.addItem(withTitle: item)
    }

    view.addSubview(jsonSelector)
    self.view = view
}

@objc func updatePointFile() {
    let file = jsonSelector.selectedItem?.title ?? "swiftLogo"
    ...
}

作品