47、Grand Central Dispatch, Background Processing, and App State Management

Grand Central Dispatch, Background Processing, and App State Management

1. Improving App Responsiveness with UI Updates

When building and running an app, initially, there were some issues like the button getting stuck in a highlighted position after being touched. To enhance the GUI, we can take the following steps:
1. Add a UIActivityIndicatorView :
- First, add a property declaration for it at the top of ViewController.swift :

class ViewController: UIViewController {
    @IBOutlet var startButton : UIButton!
    @IBOutlet var resultsTextView : UITextView!
    @IBOutlet var spinner : UIActivityIndicatorView!
}

- Then, open `Main.Storyboard`, locate an A