Swift PageController 和图像的滚动视图布局问题 iOS

Question

I can't figure out how to set constraints for a scrollView with an imageView inside. I am using the scrollView with a pageConroller to swipe thru a bunch of images.

See my layout in the picture below.

// Code for imageView

for index in 0..<drinksImagesArray.count {
        frame.origin.x = scrollView.frame.size.width * CGFloat(index)
        frame.size = scrollView.frame.size
        
        let imageView = UIImageView(frame: frame)
        imageView.contentMode = .scaleAspectFit
        imageView.image = UIImage(named: imagesArray[index].name)
        self.scrollView.addSubview(imageView)
    }
    scrollView.contentSize = CGSize(width: scrollView.frame.size.width * CGFloat(imagesArray.count), height: scrollView.frame.size.height)
    scrollView.delegate = self

Any suggestions? Thank you!

Layout

Answer 1

You will have much better luck using auto-layout --- it can handle all of the frame sizes and .contentSize for you.

Here's a quick example - it uses a view controller with a scroll view added in Storyboard, so it should be pretty easy for you to integrate with your code:

class ScrollingImagesViewController: UIViewController {
    
    @IBOutlet var scrollView: UIScrollView!
    
    var drinksImagesArray: [String] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // however you're populating your array...
        drinksImagesArray = [
            "drink1",
            "drink2",
            "drink3",
            // etc...
        ]

        // create a horizontal stack view
        let stack = UIStackView()
        stack.axis = .horizontal
        stack.alignment = .fill
        stack.distribution = .fillEqually
        stack.spacing = 0

        // add the stack view to the scroll view
        stack.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(stack)
        
        // use scroll view's contentLayoutGuide for content constraints
        let svCLG = scrollView.contentLayoutGuide
        
        NSLayoutConstraint.activate([
            
            // stack view constrained Top / Bottom / Leading / Trailing of scroll view CONTENT guide
            stack.topAnchor.constraint(equalTo: svCLG.topAnchor),
            stack.bottomAnchor.constraint(equalTo: svCLG.bottomAnchor),
            stack.leadingAnchor.constraint(equalTo: svCLG.leadingAnchor),
            stack.trailingAnchor.constraint(equalTo: svCLG.trailingAnchor),
            
            // stack view height == scroll view FRAME height
            stack.heightAnchor.constraint(equalTo: scrollView.frameLayoutGuide.heightAnchor),
            
        ])

        // create image views and add them to the stack view
        drinksImagesArray.forEach { imgName in
            let v = UIImageView()
            v.backgroundColor = .lightGray
            v.contentMode = .scaleAspectFit
            // make sure we load a valid image
            if let img = UIImage(named: imgName) {
                v.image = img
            }
            stack.addArrangedSubview(v)
        }
        
        // stack distribution is set to .fillEqually, so we only need to set the
        // width constraint on the first image view
        
        // unwrap it
        if let firstImageView = stack.arrangedSubviews.first {
            firstImageView.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor).isActive = true
        }
        
    }

}

---

Edit

After reviewing your Storyboard...

Auto-layout doesn't seem to like it when you add a UINavigationBar and a UIToolbar and a UIScrollView as subviews. In particular, it appears to confuse the scroll view's frame related constraints.

The fix is to first add constraints for your scroll view:

• Top to Navigation Bar Bottom
• Bottom to Page Control Top
• Leading and Trailing to safe-area

Storyboard / Interface builder will complain that the scroll view is not configured properly. You can either ignore that, or select the scroll view and set Ambiguity to Never Verify:

Then, in your view controller class, we need to create a height constraint for the stack view we're adding to the scroll view, and set that height constant in viewDidLayoutSubviews() .

Here's the full code:

//
//  WasserhaushaltViewController.swift
//  deSynthTheOceans
//
//  Created by robinsonhus0 on 24.03.20.
//  Copyright © 2020 robinsonhus0. All rights reserved.
//

import UIKit
import AVFoundation
import Charts
import FSCalendar
import HealthKit


struct WasserSpeicher: Codable {
    let wassermenge: Double
    let speicherdatum: String
    let speicherStelle: Double
}

class WasserhaushaltViewController: UIViewController, UIScrollViewDelegate {
    @IBOutlet weak var diagrammView: UIView!
    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var pageControl: UIPageControl!
    
    let drinksImagesArray = ["tapWater", "water", "milk", "cola", "coffee", "tea", "juice", "beer"]

    var imageIndex = Int()
    
    struct Drinks {
        var name: String
        var tagesMengeFactor: Double
        var gesamtMengeFactor: Double
    }
    
    var frame = CGRect(x: 0, y: 0, width: 0, height: 0)
    var pageNumber = CGFloat()
    
    @IBOutlet weak var todaysWaterConsumptionLabel: UILabel!
    @IBOutlet weak var waterGoalProgress: UIProgressView!
    @IBOutlet weak var waterGoalLabel: UILabel!
    @IBOutlet weak var wasserMengeStepper: UIStepper!
    @IBOutlet weak var motivationTextView: UITextView!
    @IBOutlet weak var wasserglasButton: UIBarButtonItem!
    @IBOutlet weak var kleineFlascheButton: UIBarButtonItem!
    @IBOutlet weak var grosseFlascheButton: UIBarButtonItem!
    @IBOutlet weak var overAllWaterConsumptionLabel: UILabel!
    
    // added
    let scrollingImagesStackView = UIStackView()
    var stackHeightConstraint: NSLayoutConstraint!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        pageControl.numberOfPages = drinksImagesArray.count
        setupDrinkImages()
    }
    
    
    func setupDrinkImages() {
        // set stack view properties
        scrollingImagesStackView.axis = .horizontal
        scrollingImagesStackView.alignment = .fill
        scrollingImagesStackView.distribution = .fillEqually
        scrollingImagesStackView.spacing = 0
        
        // add the stack view to the scroll view
        scrollingImagesStackView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.addSubview(scrollingImagesStackView)
        
        // use scroll view's contentLayoutGuide for content constraints
        let svCLG = scrollView.contentLayoutGuide
        
        NSLayoutConstraint.activate([
            
            // stack view constrained Top / Bottom / Leading / Trailing of scroll view CONTENT guide
            scrollingImagesStackView.topAnchor.constraint(equalTo: svCLG.topAnchor),
            scrollingImagesStackView.bottomAnchor.constraint(equalTo: svCLG.bottomAnchor),
            scrollingImagesStackView.leadingAnchor.constraint(equalTo: svCLG.leadingAnchor),
            scrollingImagesStackView.trailingAnchor.constraint(equalTo: svCLG.trailingAnchor),
            
        ])
        
        // create the stack view height constraint - it will be updated in viewDidLayoutSubviews
        stackHeightConstraint = scrollingImagesStackView.heightAnchor.constraint(equalToConstant: 0)
        stackHeightConstraint.isActive = true
        
        // create image views and add them to the stack view
        drinksImagesArray.forEach { imgName in
            let v = UIImageView()
            v.backgroundColor = .orange
            v.contentMode = .scaleAspectFit
            // make sure we load a valid image
            if let img = UIImage(named: imgName) {
                v.image = img
            }
            scrollingImagesStackView.addArrangedSubview(v)
        }
        
        // stack distribution is set to .fillEqually, so we only need to set the
        // width constraint on the first image view
        
        // unwrap it
        if let firstImageView = scrollingImagesStackView.arrangedSubviews.first {
            firstImageView.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor).isActive = true
        }

        scrollView.delegate = self
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        // since we have a UINavigationBar and a UIToolBar in the view hierarchy,
        //  we need to set this here
        //  Note: if the view size changes
        // stack view height == scroll view FRAME height
        stackHeightConstraint.constant = scrollView.frame.height
        
    }
    
//  func setupDrinkImages() {
//      for index in 0..<drinksImagesArray.count {
//          frame.origin.x = scrollView.frame.size.width * CGFloat(index)
//          frame.size = scrollView.frame.size
//
//          let imageView = UIImageView(frame: frame)
//          imageView.contentMode = .scaleAspectFit
//          imageView.image = UIImage(named: drinksImagesArray[index])
//          self.scrollView.addSubview(imageView)
//      }
//      scrollView.contentSize = CGSize(width: scrollView.frame.size.width * CGFloat(drinksImagesArray.count), height: scrollView.frame.size.height)
//      scrollView.delegate = self
//  }
    
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        pageNumber = scrollView.contentOffset.x / scrollView.frame.size.width
        pageControl.currentPage = Int(pageNumber)
    }
}

Your (modified) Storyboard is too big to add here... if you have any trouble with the changes mentioned above, here it is: https://pastebin.com/2Q1uFUgL