draw lines on all rows of a UITextView

Question

I want to draw a line in UITextView to separate lines like a notebook.

After researching, I came across the following site, but the information was out of date and could not be applied to the current version.

Is it possible to draw lines on the UITextView?

Answer 1

One approach is to create a UITextView subclass and override draw(_ rect: CGRect).

Here is an example that should get you on your way:

class LinedTextView: UITextView {
    
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        commonInit()
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        commonInit()
    }
    func commonInit() {
        // this is needed to tell the lines to redraw
        //  when the text is scrolled
        self.contentMode = .redraw
    }

    override func draw(_ rect: CGRect) {
        
        guard let context = UIGraphicsGetCurrentContext(),
              let font = self.font
        else {
            super.draw(rect)
            return
        }
        
        context.setStrokeColor(UIColor.red.cgColor)
        context.setLineWidth(1.0)
        context.beginPath()
        
        let nLines = (self.contentSize.height + self.bounds.height) / font.lineHeight

        var y: CGFloat = font.lineHeight + textContainerInset.top

        for _ in 0..<Int(nLines) {
            context.move(to: .init(x: 0.0, y: y))
            context.addLine(to: .init(x: bounds.maxX, y: y))
            y += font.lineHeight
        }

        context.strokePath()
    }
    
}

You use it just like a normal UITextView as in this example view controller:

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let testTextView = LinedTextView()
        
        testTextView.backgroundColor = .yellow
        testTextView.text =  "When a user taps a text view, a keyboard appears; when a user taps Return in the keyboard, the keyboard disappears and the text view can handle the input in an application-specific way. You can specify attributes, such as font, color, and alignment, that apply to all text in a text view."
        
        testTextView.font = .systemFont(ofSize: 28.0, weight: .regular)
        
        testTextView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(testTextView)
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            
            testTextView.topAnchor.constraint(equalTo: g.topAnchor, constant: 40.0),
            testTextView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
            testTextView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
            testTextView.heightAnchor.constraint(equalToConstant: 300.0),
            
        ])
        
    }
    
}

Looks like this when running:

Please note: this is Example Code Only!!! - it is intended to give you something to learn from and should not be considered "production ready."