Scroll Views (UIScrollView)

What is UIScrollView?

UIScrollView is a UIKit component that allows users to scroll through a content view that is larger than the screen. It supports vertical and horizontal scrolling, zooming, and paging.

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1. Key Features of UIScrollView

✅ Supports vertical & horizontal scrolling
✅ Allows zooming for images and other content
✅ Enables paging for swipe-based interfaces
✅ Handles content offset and insets for flexible layouts
✅ Works with Auto Layout and programmatic constraints

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2. How to Add UIScrollView in Storyboard

1. Drag & Drop a UIScrollView from the Object Library.
2. Set constraints (Pin edges to the Safe Area or Superview).
3. Add a UIView inside the UIScrollView (this is the content view).
4. Set constraints for the content view (Pin to ScrollView edges and set width & height if needed).
5. Add labels, images, or other UI elements inside the content view.
6. Ensure the Content Size of UIScrollView is large enough for scrolling.

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3. Implementing UIScrollView Programmatically

import UIKit

class ViewController: UIViewController {
    let scrollView = UIScrollView()
    let contentView = UIView()

    override func viewDidLoad() {
        super.viewDidLoad()

        setupScrollView()
    }

    func setupScrollView() {
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        contentView.translatesAutoresizingMaskIntoConstraints = false

        view.addSubview(scrollView)
        scrollView.addSubview(contentView)

        // Constraints for UIScrollView
        NSLayoutConstraint.activate([
            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])

        // Constraints for contentView inside UIScrollView
        NSLayoutConstraint.activate([
            contentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
            contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
            contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
            contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
            contentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor), // Ensures vertical scrolling
            contentView.heightAnchor.constraint(equalToConstant: 1200) // Set larger height for scrolling
        ])

        // Add a label to contentView
        let label = UILabel()
        label.text = "Scrollable Content"
        label.textAlignment = .center
        label.translatesAutoresizingMaskIntoConstraints = false
        contentView.addSubview(label)

        NSLayoutConstraint.activate([
            label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
            label.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 50)
        ])
    }
}

✅ This will create a vertical scrollable view with a label.

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4. Handling Scrolling Programmatically

You can modify the scroll behavior dynamically.

4.1 Adjusting Content Size Manually

scrollView.contentSize = CGSize(width: view.frame.width, height: 2000) // Makes it scrollable

4.2 Scrolling to a Specific Position

scrollView.setContentOffset(CGPoint(x: 0, y: 500), animated: true)

4.3 Detecting Scroll Events

func scrollViewDidScroll(_ scrollView: UIScrollView) {
    print("Scrolling... Current Offset: \(scrollView.contentOffset)")
}

➡️ Don’t forget to set scrollView.delegate = self and conform to UIScrollViewDelegate

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5. Zooming in UIScrollView

UIScrollView supports pinch-to-zoom when a UIImageView or similar view is added.

5.1 Enabling Zoom

scrollView.minimumZoomScale = 1.0
scrollView.maximumZoomScale = 5.0
scrollView.delegate = self

5.2 Implementing View for Zooming

func viewForZooming(in scrollView: UIScrollView) -> UIView? {
    return imageView // The view that should be zoomed
}

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6. Paging with UIScrollView

If you need a swipeable screen (like onboarding pages), enable paging.

scrollView.isPagingEnabled = true

➡️ This makes sure each page aligns perfectly when scrolling.

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7. UIScrollView with Auto Layout (Common Issues & Fixes)

❌ Issue: ScrollView Not Scrolling

✅ Fix: Ensure the contentView has constraints that define its size.

contentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor).isActive = true
contentView.heightAnchor.constraint(equalToConstant: 1500).isActive = true

❌ Issue: ScrollView Bounces Too Much

✅ Fix: Disable bounce effects

scrollView.bounces = false
scrollView.alwaysBounceVertical = false
scrollView.alwaysBounceHorizontal = false

❌ Issue: ScrollView Not Scrolling Horizontally

✅ Fix: Set explicit width

contentView.widthAnchor.constraint(equalToConstant: 1200).isActive = true

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8. Conclusion

✔️ UIScrollView is essential for handling large content in an iOS app
✔️ Supports scrolling, zooming, and paging
✔️ Works with Auto Layout and programmatic UI
✔️ Ensure correct constraints for proper functionality

Would you like a custom implementation for your project? 🚀