我无法在我的子视图中居中一个按钮，我已经被卡了好几个星期了（斯威夫特）

Question

我正在用可可豆荚（Shuffle）构建一个应用程序，其中有一个cardStack（tinder风格），每个卡片在中心包含一个单词。我正试图用下面的代码为每张卡片添加一个按钮，但是当我设法以编程方式添加按钮时，我无法将其居中：当我使用“button.center=card.center”时，按钮将保留在“卡片视图”的坐标（0,0）处。我附上了一张截图，你可以看到右上角（0,0）坐标处的圆角白色按钮，如前所述。我错在哪里？它应该是相当初级的，但我被卡住了。

import UIKit
import Shuffle


class CardsViewController: UIViewController, SwipeCardStackDataSource, SwipeCardStackDelegate {
    
    let cardStack = SwipeCardStack()
    var actualIndex : Int = 0

    var showingBack = false
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addSubview(cardStack)
        cardStack.frame.size.height = view.frame.size.height - 180
        cardStack.frame.size.width = view.frame.size.width
        cardStack.center.y =  CGFloat(cardStack.frame.size.height/2)
        cardStack.center.x =  CGFloat(cardStack.frame.size.width/2)
        cardStack.center = CGPoint(x: view.center.x, y: view.center.y + 78)
        cardStack.dataSource = self
        
//        BUTTON
        
        
        
//        NAVIGATION BAR TRANSPARENT
        
        self.navigationController?.navigationBar.setBackgroundImage(UIImage(), for: .default)
        self.navigationController?.navigationBar.shadowImage = UIImage()
        self.navigationController?.navigationBar.isTranslucent = true
        
        
//        CENTRAL BUTTON

    }
    
    
    func card(fromImage word: String) -> SwipeCard {
        let card = SwipeCard()
        card.swipeDirections = [.left, .right]
        for direction in card.swipeDirections {
          card.setOverlay(CardOverlay(direction: direction), forDirection: direction)
        }
        card.content = CardContentView(withWord: word)
        card.footer = CardFooterView(withTitle: "", subtitle: "")
        view.backgroundColor = .red
        
        let button = UIButton()
         button.frame.size = CGSize(width: 70, height: 70)
        button.layer.cornerRadius = button.frame.width/2
        button.clipsToBounds = true
        button.backgroundColor = .init(white: 1, alpha: 1)

        button.center = card.center
        
        card.addSubview(button)
            return card
    }
    
    
    func cardStack(_ cardStack: SwipeCardStack, cardForIndexAt index: Int) -> SwipeCard {
        let  theCard = card(fromImage: cardWords[actualIndex].word)
        actualIndex = actualIndex + 1
        return theCard
    }

截图

Answer 1

问题是，当您试图添加按钮时，卡框架尚未有效。

我还没有使用过这个“shuffle”pod,但是快速的查看告诉我你想要使用自动布局/约束,而不是尝试根据框架中心设置按钮的位置。

这样试试：

func card(fromImage word: String) -> SwipeCard {
    let card = SwipeCard()
    card.swipeDirections = [.left, .right]
    for direction in card.swipeDirections {
        card.setOverlay(CardOverlay(direction: direction), forDirection: direction)
    }
    card.content = CardContentView(withWord: word)
    card.footer = CardFooterView(withTitle: "", subtitle: "")
    view.backgroundColor = .red
    
    // changes begin here...
    let button = UIButton()
    // use auto-layout / constraints
    //button.frame.size = CGSize(width: 70, height: 70)
    
    button.translatesAutoresizingMaskIntoConstraints = false

    // add button to card
    card.addSubview(button)

    // button width = 70, height equalTo width
    button.widthAnchor.constraint(equalToConstant: 70.0).isActive = true
    button.heightAnchor.constraint(equalTo: button.widthAnchor).isActive = true
    
    // center it in the card view
    button.centerXAnchor.constraint(equalTo: card.centerXAnchor).isActive = true
    button.centerYAnchor.constraint(equalTo: card.centerYAnchor).isActive = true

    // frame is not yet valid, so use 70 / 2
    button.layer.cornerRadius = 35.0 //button.frame.width/2
    
    button.clipsToBounds = true
    button.backgroundColor = .init(white: 1, alpha: 1)
    
    return card
}

根据您的SwipeCard和CardContentView类设置的方式，您可能需要将按钮添加到内容视图中，而不是添加到卡本身（您没有显示那些类，所以很难猜测）。

作为附带说明：您确实应该修改SwipeCard类或CardContentView类，并在其中添加按钮...