Swift - 以编程方式在 UIView 中定位项目

Posted 2023-03-13

【中文标题】Swift - 以编程方式在 UIView 中定位项目

【英文标题】：Swift - position items inside UIView programmatically

【发布时间】：2019-11-19 16:44:02

【问题描述】：

我被困在我的项目中，因为我不知道如何以编程方式在 `UIView 中约束我的项目（UILabel、UIImageView、UITableView、...）。

问题是我的UIView .transforms 通过点击button。我知道我可以让所有项目都像我对UIView 所做的那样。但这意味着我必须为它们中的每一个设置动画，这似乎不太聪明..

那是我的UIView（灰色背景，->底栏可以忽略）

这就是我设置UIView的方式：

let wishlistView: UIView = 
    let v = UIView()
    v.translatesAutoresizingMaskIntoConstraints = false
    v.backgroundColor = .darkGray
    v.layer.cornerRadius = 30
    return v
()
view.addSubview(wishlistView)

wishlistView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 140.0),
wishlistView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0),
wishlistView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 30.0),
wishlistView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -30.0),

基本上，问题是如何限制 UIView 内的项目，因此我不必为每个项目“设置动画”。相反，我只需要对我的UIView 进行动画/转换，其余的项目就会随之而来。

我希望我的问题很清楚，我是新来的 :) 找不到关于该主题的任何内容，感谢任何帮助！

【问题讨论】：

以相同的方式添加和约束以... wishlistView.addSubview(aLabel) 后跟 aLabel.topAnchor.constraint(equalTo: wishlistView.topAnchor, constant: 12.0), 等

但是如果我移动我的UIView，该项目会随之移动吗？还是会导致错误？

你是对的！我的问题是我仍然有view.addSubview(testLabel) 而不是wishlistView.addSubview(testLabel)。谢谢！！

【参考方案1】：

你可以试试这个：

import UIKit

class ViewController: UIViewController 

    let wishlistView: UIView = 
        let v = UIView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .darkGray
        v.layer.cornerRadius = 30
        return v
    ()

    let aLabel: UILabel = 
        let v = UILabel()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .yellow
        v.text = "This is a Label"
        v.textAlignment = .center
        return v
    ()

    let theButton: UIButton = 
        let v = UIButton()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.setTitle("Tap Me", for: .normal)
        v.backgroundColor = .blue
        return v
    ()

    var openConstraint: NSLayoutConstraint!
    var closedConstraint: NSLayoutConstraint!

    override func viewDidLoad() 
        super.viewDidLoad()

        view.addSubview(theButton)

        view.addSubview(wishlistView)

        wishlistView.addSubview(aLabel)

        openConstraint = wishlistView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 140.0)
        closedConstraint = wishlistView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: 0.0)

        openConstraint.priority = .defaultLow
        closedConstraint.priority = .defaultHigh

        NSLayoutConstraint.activate ([

            theButton.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20.0),
            theButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),

            openConstraint,
            closedConstraint,

            wishlistView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: 0),
            wishlistView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 30.0),
            wishlistView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -30.0),

            aLabel.topAnchor.constraint(equalTo: wishlistView.topAnchor, constant: 16.0),
            aLabel.leadingAnchor.constraint(equalTo: wishlistView.leadingAnchor, constant: 16.0),
            aLabel.trailingAnchor.constraint(equalTo: wishlistView.trailingAnchor, constant: -16.0),

        ])

        theButton.addTarget(self, action: #selector(showHideWishlist(_:)), for: .touchUpInside)
    

    @objc func showHideWishlist(_ sender: Any?) -> Void 
        if closedConstraint.priority == .defaultHigh 
            closedConstraint.priority = .defaultLow
            openConstraint.priority = .defaultHigh
         else 
            openConstraint.priority = .defaultLow
            closedConstraint.priority = .defaultHigh
        
        UIView.animate(withDuration: 0.5) 
            self.view.layoutIfNeeded()
        
    

点击“点击我”按钮将显示/隐藏“wishlistView”：