iOS: UIActivityIndicator in UISearchBar

Found none of the advertised solutions worked well for iOS13... here is my own, which subclasses the Search Bar and should be more robust for future use

class SearchBar: UISearchBar {

    var activityIndicator: UIActivityIndicatorView?
    
    var isLoading: Bool {
        get {
            return activityIndicator != nil
        } set {
            if newValue {
                if activityIndicator == nil {
                    
                    guard let leftView = searchTextField.leftView else {
                        return
                    }
                    
                    let ai = UIActivityIndicatorView(style: .medium)
                    ai.frame = self.convert(leftView.frame, from: leftView.superview)
                    self.addSubview(ai)
                    
                    ai.startAnimating()
                    leftView.isHidden = true
                    activityIndicator = ai
                    
                }
            } else {
                activityIndicator?.removeFromSuperview()
                activityIndicator = nil
                
                guard let leftView = searchTextField.leftView else {
                    return
                }
                leftView.isHidden = false
            }
        }
    }
    
}

Update for iOS 13.

You can use below extension in Swift 4+. Usage:

To show activity : searchBar.isLoading = true

To hide activity : searchBar.isLoading = false

UISearchBar Extension

extension UISearchBar {

    public var textField: UITextField? {
        if #available(iOS 13.0, *) {
            return self.searchTextField
        } else {
            let subViews = subviews.flatMap { $0.subviews }
            guard let textField = (subViews.filter { $0 is UITextField }).first as? UITextField else {
                return nil
            }
            return textField
        }
    }

    public var activityIndicator: UIActivityIndicatorView? {
        return textField?.leftView?.subviews.flatMap{ $0 as? UIActivityIndicatorView }.first
    }

    var isLoading: Bool {
        get {
            return activityIndicator != nil
        } set {
            if newValue {
                if activityIndicator == nil {
                    let newActivityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .gray)
                    newActivityIndicator.transform = CGAffineTransform(scaleX: 0.7, y: 0.7)
                    newActivityIndicator.startAnimating()
                    newActivityIndicator.backgroundColor = UIColor.white
                    textField?.leftView?.addSubview(newActivityIndicator)
                    let leftViewSize = textField?.leftView?.frame.size ?? CGSize.zero
                    newActivityIndicator.center = CGPoint(x: leftViewSize.width/2, y: leftViewSize.height/2)
                }
            } else {
                activityIndicator?.removeFromSuperview()
            }
        }
    }
}

Yes you can.

When start searching create an activity indicator and add it as the subview of UISearchBar using addSubView method. When you finish the search remove it from the search bar using removeFromSuperView method.

UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
//set frame for activity indicator
[searchBar addSubview: spinner];
[spinner startAnimating];

Refer this link for an alternative way.