     // MARK: function
     
     public func show() {
+        guard let window = UIApplication.sharedApplication().keyWindow else { return }
+        
+        if progressView == nil {
+            progressView = initializeViewWithFrame(window.frame)
+        }
+        
         if progressView?.superview == nil {
             window.addSubview(progressView!)
             progressView?.progressAnimation(isLeftToRight, duration: duration, repeatCount: repeatCount)

    public var isLeftToRight: Bool
    public var duration: CFTimeInterval
    public var repeatCount: Float
    public var window: UIWindow
    public var progressView: MediumProgressView?
    
    init() {

        isLeftToRight = true
        duration = 2.0
        repeatCount = Float.infinity
    }
    
    public static let sharedInstance = MediumProgressViewManager()
