在 UIButton 内显示活动指示器

我想在按下 UIButton 后将其内容更改为 ActivityIndi​​cator。

我知道按钮有 imageView 和 titleLabel，但我不知道如何在其中放置活动指示器。

这就是我创建活动指标的方法：

let aiView = UIActivityIndicatorView(activityIndicatorStyle: .Gray)
aiView.startAnimating()
aiView.center = CGPointMake(0,0)
aiView.hidesWhenStopped = false

import UIKit

class LoadingButton: UIButton {
private var originalButtonText: String?
var activityIndicator: UIActivityIndicatorView!

func showLoading() {
    originalButtonText = self.titleLabel?.text
    self.setTitle("", for: .normal)
    
    if (activityIndicator == nil) {
        activityIndicator = createActivityIndicator()
    }
    
    showSpinning()
}

func hideLoading() {
    self.setTitle(originalButtonText, for: .normal)
    activityIndicator.stopAnimating()
}

private func createActivityIndicator() -> UIActivityIndicatorView {
    let activityIndicator = UIActivityIndicatorView()
    activityIndicator.hidesWhenStopped = true
    activityIndicator.color = .lightGray
    return activityIndicator
}

private func showSpinning() {
    activityIndicator.translatesAutoresizingMaskIntoConstraints = false
    self.addSubview(activityIndicator)
    centerActivityIndicatorInButton()
    activityIndicator.startAnimating()
}

private func centerActivityIndicatorInButton() {
    let xCenterConstraint = NSLayoutConstraint(item: self, attribute: .centerX, relatedBy: .equal, toItem: activityIndicator, attribute: .centerX, multiplier: 1, constant: 0)
    self.addConstraint(xCenterConstraint)
    
    let yCenterConstraint = NSLayoutConstraint(item: self, attribute: .centerY, relatedBy: .equal, toItem: activityIndicator, attribute: .centerY, multiplier: 1, constant: 0)
    self.addConstraint(yCenterConstraint)
}
}