How to display activity indicator in center of UIAlertController?

Apple does not encourage directly subclassing UIAlertController so I made a class that displays UIAlertController with centered UIActivityIndicator and handles the cancel condition with a class protocol.

import Foundation
import UIKit

protocol BusyAlertDelegate {
func didCancelBusyAlert()
}


class BusyAlert {

var busyAlertController: UIAlertController?
var presentingViewController: UIViewController?
var activityIndicator: UIActivityIndicatorView?
var delegate:BusyAlertDelegate?

init (title:String, message:String, presentingViewController: UIViewController) {
busyAlertController = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.Alert)
busyAlertController!.addAction(UIAlertAction(title: NSLocalizedString("Cancel", comment: "Cancel Button"), style: UIAlertActionStyle.Cancel, handler:{(alert: UIAlertAction!) in
delegate?.didCancelBusyAlert()
}))
self.presentingViewController = presentingViewController
activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
busyAlertController!.view.addSubview(activityIndicator!)
}

func display() {
dispatch_async(dispatch_get_main_queue(), {
self.presentingViewController!.presentViewController(self.busyAlertController!, animated: true, completion: {
self.activityIndicator!.translatesAutoresizingMaskIntoConstraints = false
self.busyAlertController!.view.addConstraint(NSLayoutConstraint(item: self.activityIndicator!, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self.busyAlertController!.view, attribute: NSLayoutAttribute.CenterX, multiplier: 1, constant: 0))
self.busyAlertController!.view.addConstraint(NSLayoutConstraint(item: self.activityIndicator!, attribute: NSLayoutAttribute.CenterY, relatedBy: NSLayoutRelation.Equal, toItem: self.busyAlertController!.view, attribute: NSLayoutAttribute.CenterY, multiplier: 1, constant: 0))
self.activityIndicator!.startAnimating()

})
})

}

func dismiss() {
dispatch_async(dispatch_get_main_queue(), {
self.busyAlertController?.dismissViewControllerAnimated(true, completion: nil)
})
}

}


I recommend using lazy var to initialize the class.

lazy var busyAlertController: BusyAlert = {
let busyAlert = BusyAlert(title: "Lengthy Task", message: "Please wait...", presentingViewController: self)
busyAlert.delegate = self
return busyAlert
}()

Here is a link to sample code:

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In swift:

activityIndicator.center = self.view.center

If you have a tool bar or a navController you might want to shift the point but otherwise, center is center...

If you still have issues, perhaps [this][1] tutorial would help. If you are trying to center it in a table view controller, [this][2] answer might help.


[1]:
[2]:

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I converted the answer to Objective C, if anyone is interested:

UIAlertController *pending = [UIAlertController alertControllerWithTitle:nil
message:@"Please wait...\n\n"
preferredStyle:UIAlertControllerStyleAlert];
UIActivityIndicatorView* indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
indicator.color = [UIColor blackColor];
indicator.translatesAutoresizingMaskIntoConstraints=NO;
[pending.view addSubview:indicator];
NSDictionary * views = @{@"pending" : pending.view, @"indicator" : indicator};

NSArray * constraintsVertical = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[indicator]-(20)-|" options:0 metrics:nil views:views];
NSArray * constraintsHorizontal = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[indicator]|" options:0 metrics:nil views:views];
NSArray * constraints = [constraintsVertical arrayByAddingObjectsFromArray:constraintsHorizontal];
[pending.view addConstraints:constraints];
[indicator setUserInteractionEnabled:NO];
[indicator startAnimating];
[self presentViewController:pending animated:YES completion:nil];

Cheers

For those like me who prefer `UIActivityIndicatorView` aligned at the left of the `UIAlertController.title`, this is my solution in **Swift** working for all devices:

let alert = UIAlertController(title: NSLocalizedString("Authenticating...", comment: "Authenticating"), message: nil, preferredStyle: .Alert);
let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray)
activityIndicator.frame = activityIndicator.frame.rectByOffsetting(dx: 8, dy: (alert.view.bounds.height - activityIndicator.frame.height)/2);
activityIndicator.autoresizingMask = .FlexibleRightMargin | .FlexibleTopMargin | .FlexibleBottomMargin
activityIndicator.color = themeManager().currentTheme.navigationBarTintColor;
activityIndicator.startAnimating();
alert.view.addSubview(activityIndicator);
self.presentViewController(progressAlert, animated: true, completion: nil);

However, to align the `UIActivityIndicatorView` in the view center you can change as follows:

activityIndicator.center = CGPoint(x: (alert.view.bounds.width)/2, y: (alert.view.bounds.height)/2)
activityIndicator.autoresizingMask = .FlexibleLeftMargin | .FlexibleRightMargin | .FlexibleTopMargin | .FlexibleBottomMargin

Try this:

activityView.center = CGPointMake(self.view.bounds.size.width/2.0, self.view.bounds.size.height / 2.0)

Also you will need to check for landscape mode and reverse width and height.

if(landscapeMode)activityView.center = CGPointMake(self.view.bounds.size.height/2.0, self.view.bounds.size.width / 2.0)
Maybe you can get the alert view position?

alert.view.frame.origin.x
alert.view.frame.origin.y

and use that to place your activity view dynamically ie with the variables?

Of course you might also want to get the size divide by 2 and add that so that its centred as well.

alert.view.frame.size.height
alert.view.frame.size.width

Well try this code.

UIAlertController *alert = [UIAlertController alertControllerWithTitle:nil
message:@"Creating new user\n\n\n"
preferredStyle:UIAlertControllerStyleAlert];

UIActivityIndicatorView *loader = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
loader.center = CGPointMake(130.5, 65.5);
loader.color = [UIColor blackColor];
[loader startAnimating];
[alert.view loader];
[self presentViewController:alert animated:NO completion:nil];