UIActivityIndicatorView没有出现

Question

我正在尝试实现一个在用户处于应用程序购买过程中运行的UIActivityIndicatorView。由于某些原因，即使我已经创建了视图的子视图，UIActivityIndicatorView也不会出现。

class RemoveAdsViewController: UIViewController {

@IBAction func btnAdRemoval(sender: UIButton) {
    let buyProgress = UIActivityIndicatorView(activityIndicatorStyle: .White)
    buyProgress.center = self.view.center
    self.view.addSubview(buyProgress)
    buyProgress.startAnimating()
    print(buyProgress)
    PFPurchase.buyProduct("", block: { (error:NSError?) -> Void in
        if error != nil{
            let alert = UIAlertController(title: "Error", message: error?.localizedDescription, preferredStyle: UIAlertControllerStyle.Alert)

            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))

            self.presentViewController(alert, animated: true, completion: nil)
        }
    })
    buyProgress.stopAnimating()
    buyProgress.removeFromSuperview()
}

PFRestore：

restoreProgress.startAnimating()
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), {
       PFPurchase.restore()
       dispatch_async(dispatch_get_main_queue(), {
           restoreProgress.stopAnimating()
       })
 })

Answer 1

再看一看，问题很简单。停止并移除活动指示器太快了。您需要停止并在完成块中删除它。

@IBAction func btnAdRemoval(sender: UIButton) {
    let buyProgress = UIActivityIndicatorView(activityIndicatorStyle: .White)
    buyProgress.center = self.view.center
    self.view.addSubview(buyProgress)
    buyProgress.startAnimating()
    print(buyProgress)
    PFPurchase.buyProduct("", block: { (error:NSError?) -> Void in
        buyProgress.stopAnimating()
        buyProgress.removeFromSuperview()

        if error != nil{
            let alert = UIAlertController(title: "Error", message: error?.localizedDescription, preferredStyle: UIAlertControllerStyle.Alert)

            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))

            self.presentViewController(alert, animated: true, completion: nil)
        }
    })
}

还需要确保完成块的内容是在主线程上完成的。

Answer 2

问题是你这么做

buyProgress.startAnimating()

紧随其后的是

buyProgress.stopAnimating()

因为PFPurchase.buyProduct是一个异步调用，它将立即返回，而您没有看到您的活动指示符是在一个运行循环循环中发生的。

你得走了

buyProgress.stopAnimating()

在封闭里面，就像这样

PFPurchase.buyProduct("", block: { (error:NSError?) -> Void in
            if error != nil{
                let alert = UIAlertController(title: "Error", message: error?.localizedDescription, preferredStyle: UIAlertControllerStyle.Alert)
                buyProgress.stopAnimating()

                alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))

                self.presentViewController(alert, animated: true, completion: nil)
            }
        })