iOS动态更换Icon的全过程记录

// If false, alternate icons are not supported for the current process.
@available(iOS 10.3, *)
open var supportsAlternateIcons: Bool  get 
  
// Pass `nil` to use the primary application icon. The completion handler will be invoked asynchronously on an arbitrary background queue; be sure to dispatch back to the main queue before doing any further UI work.
@available(iOS 10.3, *)
open func setAlternateIconName(_ alternateIconName: String?, completionHandler: ((Error?) -> Void)? = nil)
  
// If `nil`, the primary application icon is being used.
@available(iOS 10.3, *)
open var alternateIconName: String?  get 

@IBAction func changeOneClick(_ sender: Any) 
  if UIApplication.shared.supportsAlternateIcons 
    UIApplication.shared.setAlternateIconName("lambot")  (error) in
      if error != nil 
        print("更换icon错误")
      
    
  

@IBAction func resetClick(_ sender: Any) 
  if UIApplication.shared.supportsAlternateIcons 
    UIApplication.shared.setAlternateIconName(nil)  (error) in
      if error != nil 
        print("更换icon错误")
      
    
  

extension UIViewController 
  public class func initializeMethod() 
    if self != UIViewController.self 
      return
    
		// Method Swizzling
    DispatchQueue.once(token: "ChangeIcon") 
      let orignal = class_getInstanceMethod(self, #selector(UIViewController.present(_:animated:completion:)))
      let swizzling = class_getInstanceMethod(self, #selector(UIViewController.jt_present(_:animated:completion:)))

      if let old = orignal, let new = swizzling 
        method_exchangeImplementations(old, new)
      
    
  

  @objc private func jt_present(_ viewControllerToPresent: UIViewController, animated flag: Bool, completion: (() -> Void)? = nil) 
    // 在这里判断是否是更换icon时的弹出框
    if viewControllerToPresent is UIAlertController 

      let alertTitle = (viewControllerToPresent as! UIAlertController).title
      let alertMessage = (viewControllerToPresent as! UIAlertController).message

      // 更换icon时的弹出框，这两个string都为nil。
      if alertTitle == nil && alertMessage == nil 
        return
      
    
		
		// 因为方法已经交换，这个地方的调用就相当于调用原先系统的 present
    self.jt_present(viewControllerToPresent, animated: flag, completion: completion)
  

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: UIApplication.LaunchOptionsKey: Any?) -> Bool 

  UIViewController.initializeMethod()

  return true

extension DispatchQueue 
  private static var _onceTracker = ()
  public class func once(token: String, block: () -> ()) 
    objc_sync_enter(self)
    defer 
      objc_sync_exit(self)
    
    if _onceTracker.contains(token) 
      return
    
    _onceTracker.append(token)
    block()