我试图在用户点击登录按钮时显示活动指示器。如果我把startActivityIndicator()代码在viewDidLoad()它完全按照预期显示在屏幕上。当我将其作为第一步执行时btnSignIn()它永远不会出现。有点迷失，所以我希望堆栈大师能提供帮助......
// Here are the variable declarations
var activityIndicator: UIActivityIndicatorView = UIActivityIndicatorView()
var loadingView: UIView = UIView()
var viewCenter:CGPoint!
@IBAction func btnSignIn(sender: AnyObject) {
startActivityIndicator()
if validateEmailAddress(txtEmailAddress.text!) == false {
stopActivityIndicator(self.loadingView)
return
}
if validatePassword(txtPassword.text!) == false {
stopActivityIndicator(self.loadingView)
return
}
PFUser.logInWithUsernameInBackground(txtEmailAddress.text!, password:txtPassword.text!) {
(user: PFUser?, error: NSError?) -> Void in
if user != nil {
// Successful login.
self.txtPassword.resignFirstResponder()
self.txtEmailAddress.resignFirstResponder()
self.getUserInfo()
} else {
self.stopActivityIndicator(self.loadingView)
// The login failed. Display alert.
self.displayAlert("Whoops!", message: "Email or Password are incorrect.")
}
}
}
func startActivityIndicator() {
loadingView.frame = CGRectMake(0, 0, 80, 80)
loadingView.center = viewCenter
print(viewCenter)
loadingView.backgroundColor = UIColorFromRGB("444444", alpha: 0.7)
loadingView.clipsToBounds = true
loadingView.layer.cornerRadius = 10
activityIndicator.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyle.WhiteLarge
activityIndicator.center = CGPointMake(loadingView.frame.size.width / 2, loadingView.frame.size.height / 2);
view.addSubview(loadingView)
loadingView.addSubview(activityIndicator)
UIApplication.sharedApplication().beginIgnoringInteractionEvents()
activityIndicator.startAnimating()
}
func stopActivityIndicator(uiView: UIView) {
activityIndicator.stopAnimating()
loadingView.removeFromSuperview()
UIApplication.sharedApplication().endIgnoringInteractionEvents()
}
使用我的delay实用程序（参见此处：https://stackoverflow.com/a/24318861/341994 https://stackoverflow.com/a/24318861/341994），重写如下：
@IBAction func btnSignIn(sender: AnyObject) {
startActivityIndicator()
delay(0.1) {
if validateEmailAddress(txtEmailAddress.text!) == false {
// ... everything else goes here ...
}
}
延迟使活动指示器有机会出现并开始旋转。
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