Scrolling, or "Rolagem" in Portuguese, is a fundamental aspect of user interface design, especially in mobile applications where screen real estate is limited. In the Apple ecosystem, particularly in iOS development, scrolling is typically implemented using components like UIScrollView, UITableView, and UICollectionView. These components allow developers to present content that extends beyond the visible area of the screen, enabling users to scroll through the content smoothly.

This article will walk you through the basics of implementing scrolling in an iOS application using Swift. We will cover the creation and configuration of a UIScrollView and provide practical examples to help you understand how to use this component effectively.

Examples:

1. Creating a Simple UIScrollView:

   To create a basic UIScrollView, you need to add it to your view hierarchy and set its content size. Here is a simple example in Swift:

   import UIKit
   
   class ViewController: UIViewController {
   
      override func viewDidLoad() {
          super.viewDidLoad()
   
          // Create a UIScrollView
          let scrollView = UIScrollView()
          scrollView.frame = view.bounds
          scrollView.backgroundColor = .lightGray
   
          // Create a content view
          let contentView = UIView()
          contentView.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: 1000)
          contentView.backgroundColor = .white
   
          // Add content view to scroll view
          scrollView.addSubview(contentView)
   
          // Set content size of scroll view
          scrollView.contentSize = contentView.bounds.size
   
          // Add scroll view to main view
          view.addSubview(scrollView)
      }
   }

   In this example, we create a UIScrollView and a content view that is larger than the screen. The content view is added to the scroll view, and the scroll view's content size is set to match the size of the content view.

2. Using Auto Layout with UIScrollView:

   When using Auto Layout, you need to ensure that the constraints are set up correctly to allow scrolling. Here's an example:

   import UIKit
   
   class ViewController: UIViewController {
   
      override func viewDidLoad() {
          super.viewDidLoad()
   
          let scrollView = UIScrollView()
          scrollView.translatesAutoresizingMaskIntoConstraints = false
          view.addSubview(scrollView)
   
          NSLayoutConstraint.activate([
              scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
              scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
              scrollView.topAnchor.constraint(equalTo: view.topAnchor),
              scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
          ])
   
          let contentView = UIView()
          contentView.translatesAutoresizingMaskIntoConstraints = false
          scrollView.addSubview(contentView)
   
          NSLayoutConstraint.activate([
              contentView.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor),
              contentView.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor),
              contentView.topAnchor.constraint(equalTo: scrollView.topAnchor),
              contentView.bottomAnchor.constraint(equalTo: scrollView.bottomAnchor),
              contentView.widthAnchor.constraint(equalTo: scrollView.widthAnchor),
              contentView.heightAnchor.constraint(equalToConstant: 1000)
          ])
      }
   }

   In this example, we use Auto Layout to position the UIScrollView and its content view. The content view's height is set to 1000 points, which makes the scroll view scrollable.

3. Implementing UITableView for Scrolling Lists:

   UITableView is a powerful component for displaying scrollable lists of data. Here’s a simple example:

   import UIKit
   
   class ViewController: UIViewController, UITableViewDataSource {
   
      let tableView = UITableView()
   
      override func viewDidLoad() {
          super.viewDidLoad()
   
          tableView.frame = view.bounds
          tableView.dataSource = self
          view.addSubview(tableView)
      }
   
      // UITableViewDataSource methods
      func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
          return 20
      }
   
      func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
          let cell = tableView.dequeueReusableCell(withIdentifier: "cell") ?? UITableViewCell(style: .default, reuseIdentifier: "cell")
          cell.textLabel?.text = "Row \(indexPath.row)"
          return cell
      }
   }

   In this example, we create a UITableView and set its data source to the view controller. The UITableViewDataSource methods are implemented to provide the data for the table view.