如何向 UIAlertController 添加进度条？

我想在 swift iOS 8 UIAlertController 中添加进度条。这可能吗？ 有没有办法继承 UIAlertController 并添加进度条并连接一些委托函数？

thanks

如果您只需要一个进度条，只需将其添加为子视图，如下所示：

更新为 Swift 5：

//  Just create your alert as usual:
let alertView = UIAlertController(title: "Please wait", message: "Need to download some files.", preferredStyle: .alert)
alertView.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

//  Show it to your users
present(alertView, animated: true, completion: {
    //  Add your progressbar after alert is shown (and measured)
    let margin:CGFloat = 8.0
    let rect = CGRect(x: margin, y: 72.0, width: alertView.view.frame.width - margin * 2.0 , height: 2.0)
    self.progressView = UIProgressView(frame: rect)
    self.progressView!.progress = 0.5
    self.progressView!.tintColor = self.view.tintColor
    alertView.view.addSubview(self.progressView!)
})

斯威夫特2.0：

//  Just create your alert as usual:
let alertView = UIAlertController(title: "Please wait", message: "Need to download some files.", preferredStyle: .Alert)
alertView.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))

//  Show it to your users
presentViewController(alertView, animated: true, completion: {
    //  Add your progressbar after alert is shown (and measured)
    let margin:CGFloat = 8.0
    let rect = CGRectMake(margin, 72.0, alertView.view.frame.width - margin * 2.0 , 2.0)
    let progressView = UIProgressView(frame: rect)
    progressView.progress = 0.5
    progressView.tintColor = UIColor.blueColor()
    alertView.view.addSubview(progressView)
})

调整大小相当困难UIAlertController对于更大的内容，但对于进度条，这应该可以解决问题。