当视图获得关键焦点时,Cocoa NSVIew会发出通知吗？

import Cocoa

class CustomView: NSView {
    override func becomeFirstResponder() -> Bool {
        let result = super.becomeFirstResponder()
        if result {
            Swift.print("Custom view gained focus")
        }
        return result
    }

    override func resignFirstResponder() -> Bool {
        let result = super.resignFirstResponder()
        if result {
            Swift.print("Custom view lost focus")
        }
        return result
    }
}