ios - UIAlertView with UITextField is being delayed -

i'm trying run this example. alert view text field being delayed before showing , freezes ui cannot perform anything. why happening? normal uialertview without text fields work fine when adding text fields hangs few seconds before showing.

i tried running code in clean project without other codes 1 button , still same problem:

- (ibaction)btn:(id)sender {  uialertview *alert = [[uialertview alloc] initwithtitle:@"title"                                                     message:@"message"                                                    delegate:self                                           cancelbuttontitle:@"done"                                           otherbuttontitles:nil];     alert.alertviewstyle = uialertviewstyleplaintextinput;     [alert show];    } 

i'm running on ios 8.4.