Understanding Delayed Window Loading on iOS Devices Using Objective-C and Swift.

Understanding Delayed Window Loading on iOS Devices

When it comes to loading multiple screens or windows with delays, the process can be complex and nuanced. In this article, we’ll delve into the specifics of how to load another window with a delay on iPhone devices using Objective-C and Swift.

Background: Understanding the Basics of iOS Development

To tackle this problem, we need to understand some fundamental concepts in iOS development:

NSThread: This is used to create separate threads for different tasks. In our case, we’re interested in creating a new thread that sleeps for 2 seconds before performing another task.
NSTimer: This is used to schedule events at specific intervals or after a certain amount of time has passed.

Understanding the Problem

The problem presented in the question arises when trying to display two screens simultaneously with delays. The goal is to show the first screen for 2 seconds, followed by the second screen. However, simply using NSThread sleepForTimeInterval:2.0 doesn’t work as expected because it blocks the main thread and prevents any further execution until the delay has passed.

Solution Overview

To achieve our desired outcome, we’ll use a combination of NSTimer and swapViews: to create the illusion of loading another window with delays. Here’s how it works:

We schedule an event using NSTimer that will trigger after 2 seconds.
In this scheduled timer block, we swap the views (i.e., present one view on top of the other).
By doing so, the second screen is displayed on top of the first screen, creating the illusion that the second screen was loaded with a delay.

Writing the Code

Now let’s dive into the code implementation:

Swift Version

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Add the first screen as subview of the app window.
        self.view.addSubview(firstScreen)
        
        // Schedule the timer to trigger after 2 seconds and swap views.
        let timer = Timer.scheduledTimer(withTimeInterval: 2.0,
                                          repeats: false,
                                          block: { [weak self] in
                                            // Add the second screen as subview of the app window.
                                            self?.view.addSubview(self!.secondScreen)
                                            
                                            // Remove the first screen from view hierarchy.
                                            self?.firstScreen.removeFromSuperview()
                                            
                                        })
        
    }
    
    var firstScreen = UIView() {
        didSet {
            // Set up your first screen here...
        }
    }
    
    var secondScreen = UIView() {
        didSet {
            // Set up your second screen here...
        }
    }
}

Objective-C Version

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@property (nonatomic, strong) UIView *firstScreen;
@property (nonatomic, strong) UIView *secondScreen;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // Add the first screen as subview of the app window.
    self.firstScreen = [[UIView alloc] init];
    // Set up your first screen here...
    [self.view addSubview:self.firstScreen];
    
    // Schedule the timer to trigger after 2 seconds and swap views.
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0
                                                        target:self
                                                      selector:@selector(swapViews)
                                                      userInfo:nil
                                                    repeats:NO];
}

- (void)swapViews {
    // Add the second screen as subview of the app window.
    self.secondScreen = [[UIView alloc] init];
    // Set up your second screen here...
    [self.view addSubview:self.secondScreen];
    
    // Remove the first screen from view hierarchy.
    [self.firstScreen removeFromSuperview];
}

@end

Discussion and Explanation

NSTimer: This is used to schedule an event at a specific interval or after a certain amount of time has passed. In our case, we use NSTimer to trigger after 2 seconds.
swapViews: This method is called when the scheduled timer block is triggered. Inside this block, we swap the views by adding one view on top of another.

Conclusion

Loading multiple screens with delays can be achieved using a combination of Objective-C and Swift programming languages. By leveraging NSTimer to schedule events and swapViews: to swap views, we can create the illusion of loading another window with delays.

Last modified on 2024-10-19