如何使用UIScrollView滾動到第一個視圖的頂部？

我目前有一個 UIScrollView，其 UIImageView（頂部影像）位于 UINavigationBar 下方。但是，我想將 UIImageView 定位在螢屏的最頂部（底部影像）。有沒有辦法實作這個？

到目前為止我已經嘗試過：我添加了一個 UIScrollView 擴展（

extension UIScrollView {

    // Scroll to a specific view so that it's top is at the top our scrollview
    func scrollToView(view:UIView, animated: Bool) {
        if let origin = view.superview {
            // Get the Y position of your child view
            let childStartPoint = origin.convert(view.frame.origin, to: self)
            // Scroll to a rectangle starting at the Y of your subview, with a height of the scrollview
            self.scrollRectToVisible(CGRect(x:0, y:childStartPoint.y,width: 1,height: self.frame.height), animated: animated)
        }
    }

    // Bonus: Scroll to top
    func scrollToTop(animated: Bool) {
        let topOffset = CGPoint(x: 0, y: -contentInset.top)
        setContentOffset(topOffset, animated: animated)
    }

    // Bonus: Scroll to bottom
    func scrollToBottom() {
        let bottomOffset = CGPoint(x: 0, y: contentSize.height - bounds.size.height   contentInset.bottom)
        if(bottomOffset.y > 0) {
            setContentOffset(bottomOffset, animated: true)
        }
    }

}

class MealDetailsVC: UIViewController {
    private var mealInfo: MealInfo
    
    init(mealInfo: MealInfo) {
        self.mealInfo = mealInfo
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupViews()
        scrollView.scrollToView(view: iv, animated: false)  // used extension from above
    }
    
    lazy var scrollView: UIScrollView = {
        let scrollView = UIScrollView()
        
        return scrollView
    }()
    
    lazy var iv: UIImageView = {
        let iv = UIImageView()
        iv.image = Image.defaultMealImage!   
        iv.contentMode = .scaleAspectFill
        
        return iv
    }()
}

extension MealDetailsVC {
    func setupViews() {
        addBackButton()
        addSubviews()
        autoLayoutViews()
        constrainSubviews()
    }

    fileprivate func addBackButton() {
        ...
    }
    
    @objc func goBack(sender: UIBarButtonItem) {
        ...
    }

    fileprivate func addSubviews() {
        view.addSubview(scrollView)
        scrollView.addSubview(iv)
    }
    
    fileprivate func autoLayoutViews() {
        scrollView.translatesAutoresizingMaskIntoConstraints = false
        iv.translatesAutoresizingMaskIntoConstraints = false
    }

    fileprivate func constrainSubviews() {
        NSLayoutConstraint.activate([
            scrollView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            scrollView.widthAnchor.constraint(equalTo: view.widthAnchor),
            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
        ])
        
        NSLayoutConstraint.activate([
            iv.topAnchor.constraint(equalTo: scrollView.topAnchor),
            iv.widthAnchor.constraint(equalTo: scrollView.widthAnchor),
            iv.heightAnchor.constraint(equalTo: iv.widthAnchor, multiplier: 0.6)
        ])
    }
}

uj5u.com熱心網友回復：

這可能會有所幫助。

scrollView.contentInsetAdjustmentBehavior = .never

了解更多資訊，

此屬性指定如何使用安全區域插入來修改滾動視圖的內容區域。此屬性的默認值為 UIScrollViewContentInsetAdjustmentAutomatic。

uj5u.com熱心網友回復：

不要設定高度錨并添加一個centerXAnchor等于 ScrollViewcenterXAnchor約束的 imageView。將 imageView.contentMode 設定為.scaleAspectFit

標籤：IOS 迅速 合适的视图 uiscrollview uikit

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