Slow load time with UITextView as compared to UITextField

Question

I am working on a project that creates a form dynamically based on an XML file. Everything works fine, except that if a form has too many textViews, it loads very slowly. Analyzing the app performance through xcode Time profiler, I came to know that whenever a textView is initailized it consumes a lot of CPU.

To make this easier to understand, I created a sample project that recreates this issue. The sample project just adds about 1000 UITextViews when a ViewController is loaded. I checked the performance of this code using Xcode Profiler. I was able to figure out that if UITextView is replaced by UITextField, the performance increases dramatically. The demo project would show a slight improvement since the view is limited with just textviews or textfields. But in my actual app, I see an improvement of 4 seconds minimum when I try to load a heavy XML.

Sample Project: https://github.com/amrit42087/TextView_Performance

Here is the screenshot of the Xcode Profiler with UITextView:

Here is the screenshot of the Xcode Profiler with UITextField:

UITextField reduces the load time to 960 ms from 1.49 seconds which is in case of UITextView. My actual project notices quite a lot of improvement since that is a heavy application.

Question: If anyone could suggest a solution to improve the performance while using a UITextView, that would be greatly appreciated. Using UITextField is not an option since I need multiline text.

Answer 1

Since we have no idea what else you might be doing...

One thing to try is to use a UIView subclass that contains a label and a text view. Only show the text view after tapping on the label.

Try replacing your SecondViewController with this:

class SecondViewController: UIViewController {

    let scrollView = UIScrollView()
    let stackView = UIStackView()
    
    var myData: [String] = []
    
    let spinner = UIActivityIndicatorView()
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .yellow
    
        scrollView.backgroundColor = UIColor(white: 0.95, alpha: 1.0)
        scrollView.keyboardDismissMode = .onDrag

        stackView.axis = .vertical
        stackView.spacing = 20
        
        stackView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(stackView)
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(scrollView)
        
        let g = view.safeAreaLayoutGuide
        let cg = scrollView.contentLayoutGuide
        let fg = scrollView.frameLayoutGuide
        
        NSLayoutConstraint.activate([
            
            scrollView.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
            scrollView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            scrollView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
            scrollView.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -20.0),

            stackView.topAnchor.constraint(equalTo: cg.topAnchor, constant: 8.0),
            stackView.leadingAnchor.constraint(equalTo: cg.leadingAnchor, constant: 8.0),
            stackView.trailingAnchor.constraint(equalTo: cg.trailingAnchor, constant: 0.0),
            stackView.bottomAnchor.constraint(equalTo: cg.bottomAnchor, constant: -8.0),
            
            stackView.widthAnchor.constraint(equalTo: fg.widthAnchor, constant: -16.0),

        ])

        spinner.style = .large
        spinner.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(spinner)
        spinner.hidesWhenStopped = true
        spinner.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        spinner.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        spinner.startAnimating()
        
        myData = (1...1000).compactMap({ "Element \($0)" })

        DispatchQueue.main.asyncAfter(deadline: .now() + 0.05, execute: {
            self.addTheViews()
        })
    }

    func addTheViews() {
        let start = CFAbsoluteTimeGetCurrent()
        
        let n: Int = 1000
        for i in 0..<n {
            addTextView(i)
        }
        
        let diff = CFAbsoluteTimeGetCurrent() - start
        print("Took \(diff) seconds")
        
        spinner.stopAnimating()
    }
    
    private func addTextView(_ idx: Int) {
        let textView = MyTextView()
        textView.myID = idx
        textView.text = myData[idx]
        textView.backgroundColor = .white
        textView.heightAnchor.constraint(equalToConstant: 120.0).isActive = true
        stackView.addArrangedSubview(textView)
    }
    
}

and an example MyTextView class:

class MyTextView: UIView, UITextViewDelegate {
    
    public var myID: Int = 0
    
    public var text: String = "" {
        didSet { label.text = text }
    }
    
    public var textChanged: ((Int, String) -> ())?
    
    private let label = UILabel()
    private var textView: UITextView!
    private var tap: UITapGestureRecognizer!
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    private func commonInit() {
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        addSubview(label)
        let g = self
        NSLayoutConstraint.activate([

            label.topAnchor.constraint(equalTo: g.topAnchor, constant: 8.0),
            label.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 5.0),
            label.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -5.0),
            label.bottomAnchor.constraint(lessThanOrEqualTo: g.bottomAnchor, constant: 0.0),
            
        ])
        
        tap = UITapGestureRecognizer(target: self, action: #selector(gotTap(_:)))
        addGestureRecognizer(tap)
        
    }
    @objc func gotTap(_ g: UITapGestureRecognizer) {
        if textView == nil {
            textView = UITextView()
            if let f = label.font {
                textView.font = f
            }
        }
        textView.text = self.text
        textView.frame = self.bounds
        textView.autoresizingMask = [.flexibleHeight, .flexibleWidth]
        addSubview(textView)
        
        textView.delegate = self
        
        textView.becomeFirstResponder()
    }
    func textViewDidChange(_ textView: UITextView) {
        textChanged?(myID, textView.text ?? "")
    }
    func textViewDidBeginEditing(_ textView: UITextView) {
        removeGestureRecognizer(tap)
    }
    func textViewDidEndEditing(_ textView: UITextView) {
        textView.removeFromSuperview()
        addGestureRecognizer(tap)
    }
    
}

This is, of course, just a "starting point" but my be helpful.