毕竟，似乎没有简单，直接的方法来使自定义按钮显示系统的Airplay菜单.

After all it seems there is no easy and straightforward way to make a custom button display the system's Airplay menu.

但是，@ totiG指向我一个有趣的资源，我创建了一个脚本，该脚本在屏幕可见区域之外创建了标准的音量控制，并模拟了对Airplay按钮的点击:

However, @totiG pointer me to an interesting resource and I created a script that creates the standard Volume Control outside of the visible area of the screen a simulates a click on the Airplay button:

func showAirplay() {
    let rect = CGRect(x: -100, y: 0, width: 0, height: 0)
    let airplayVolume = MPVolumeView(frame: rect)
    airplayVolume.showsVolumeSlider = false
    self.view.addSubview(airplayVolume)
    for view: UIView in airplayVolume.subviews {
        if let button = view as? UIButton {
            button.sendActions(for: .touchUpInside)
            break
        }
    }
    airplayVolume.removeFromSuperview()
}

运行此代码后，将出现以下弹出菜单:

After running this code the following popup menu appears: