Question

Im displaying an activity indicator with an Alert View using:

 UIAlertView *Alert= [[UIAlertView alloc] initWithTitle:@"Loading"
                                               message:@"\n"
                                              delegate:self
                                     cancelButtonTitle:nil
                                     otherButtonTitles:nil];

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];   
spinner.center = CGPointMake(139.5, 75.5); 
[Alert addSubview:spinner];
[spinner startAnimating];
[Alert show];    

[Alert dismissWithClickedButtonIndex:0 animated:YES];

The only thing is it disappears off the screen real quick, I would like to specify how long the alert stays on screen for, say two seconds, rather than the nano second its displayed for now. Im unsure how to go about/implement this, would I use some sort of NSTimer, if so some advice how to implement this would be very much appreciated. Thanks.

Answer 1

Here is an example of how I would go about solving the problem using NSTimer and NSInvocation. I have not tested it, so might have some trouble with it.

UIAlertView *Alert= [[UIAlertView alloc] initWithTitle:@"Loading"
                                               message:@"\n"
                                              delegate:self
                                     cancelButtonTitle:nil
                                     otherButtonTitles:nil];
UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];   
spinner.center = CGPointMake(139.5, 75.5); 
[Alert addSubview:spinner];
[spinner startAnimating];
[Alert show];  
NSMethodSignature *mySignature = [UIAlertView instanceMethodSignatureForSelector:@selector(dismissWithClickedButtonIndex:animated:)];
NSInvocation *myInvocation = [NSInvocation invocationWithMethodSignature:mySignature];
[myInvocation setSelector:@selector(dismissWithClickedButtonIndex:animated:)];
[myInvocation setTarget:Alert];
int buttonIndex = 0;
bool isAnimated = YES;
[myInvocation setArgument:&buttonClicked 
                  atIndex:2];
[myInvocation setArgument:&isAnimated 
                  atIndex:3];
NSTimer *t = [NSTimer scheduledTimerWithTimeInterval:2 
                                          invocation:myInvocation 
                                             repeats:NO];  

I still do not think this is the best answer to the question though. In most cases you should use the indicator until the work to be done is complete, not based on a time, especially not a time that can change or dependent on other factors.

So the correct answer would be wait until the work is done and at that point dismiss the UIAlertView.