lagging when push uiviewcontroller - ios

Question

When I use storyboard segue, it is pretty smooth showing another viewcontroller onscreen. However, when I'm not using storyboard, just add a simple line of code with navigationController?.pushViewController(UIViewController(), animated: true), it's a little bit lagging in transition.
Also I read about Delay when pushing view controller (iOS). But even when I'm pushing an brand new viewcontroller (no extra code inside), the transition is still a little bit lagging, any idea?

Answer 1

Swift 5.3, Xcode 12
I was facing this same issue, tried adding to main thread, but apparently the problem was I was pushing the viewController created programatically, and it backgroundColor was nil.
Just by setting the color in pushedViewController to something else, solved the issue.
self.view.backgroundColor = yourColor

Answer 2

In app delegate, set your window's background color to red.
window?.backgroundColor = .red
Also in the the pushed view controller, set its view to red.
view.backgroundColor = .red
I experienced the same issue when programmatically embedding my view controller in a UINavigationController.

Answer 3

I came across the same issue when I was drawing UI programmatically.
In my case, overriding loadView function solved my problem.
import UIKit
class MyViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
self.navigationItem.title = "My tasks"
}
override func loadView() {
// You can load your view here. For simplicity, I just give it a background color
let v = UIView()
v.backgroundColor = UIColor.orange
view = v // This line does the magic
}
}

Answer 4

Viewcontroller is expecting to render view so add below view background color or set title
override func viewDidLoad() {
super.viewDidLoad()
self.navigationItem.title = "Title"
self.view.backgroundColor = .red
}

Answer 5

I debug with slow animation on simulator. The "lagging" is the underlying previous view controller’s view as #yesleon mentioned. I set the previous view's alpha to 0 when viewWillDisappear, and 1 when viewWillAppear. It seems much better when pushing to the new controller now, but when pushing back to original view controller, it still a little bit not perfect, any better solution?
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
self.tabBarController?.tabBar.isHidden = false
view.alpha = 1.0
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
self.tabBarController?.tabBar.isHidden = true
view.alpha = 0.0
}
#IBAction func barbuttonDidTapped(_ sender: UIBarButtonItem) {
navigationController?.pushViewController(UIViewController(), animated: true)
}

Answer 6

I met the same issue, put ui code and its constraints inside viewDidLoad into loadView() fix it. Now the animation is moving smoothly.
Refer here: https://stackoverflow.com/a/3424052/10158398
loadView is the method that actually sets up your view (sets up all
the outlets, including self.view).
viewDidLoad you can figure out by its name. It's a delegate method
called after the view has been loaded (all the outlets have been set)
that just notifies the controller that it can now start using the
outlets.
viewDidLoad: "This method is called after the view controller has
loaded its associated views into memory. This method is called
regardless of whether the views were stored in a nib file or created
programmatically in the loadView method."
loadView: "If you create your views manually, you must override this
method and use it to create your views."
For an example:
class DetailViewController: UIViewController {
let imageView = UIImageView()
var picture: Picture?
override func viewDidLoad() {
super.viewDidLoad()
}
override func loadView() {
view = UIView()
view.backgroundColor = .white
imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.contentMode = .scaleAspectFit
view.addSubview(imageView)
NSLayoutConstraint.activate([
imageView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
imageView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
imageView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
])
if let picture = picture {
let path = getDocumentDirectory().appendingPathComponent(picture.picture)
imageView.image = UIImage(contentsOfFile: path.path)
}
}