ios - 从 XIB 加载 View 作为 ScrollView 的 subview

Question

我仍然是 SO 和 Swift 的新手，所以请耐心等待并随意跳过这个问题:-)

在 XIB 的 awakeFromNib 中，我想加载一些 View 作为 UIScrollView 的 subview (基本上，XIB 包含一个 ScrollView 、一个标签和一个按钮)。

如果在循环中我加载动态创建的 View ， ScrollView 将完美工作，例如。

 let customView = UIView(frame: CGRect(x: 0, y: 0, width: 300, height: 150))
 customView.frame = CGRect(x: i*300 , y: 0, width: 300, height: 150)
 customView.translatesAutoresizingMaskIntoConstraints = false
 scrollView.addSubview(customView)

但我有不同的目标。

在另一个 XIB 中，我有一个 ImageView 和一个带有一些标签的堆栈 View 。此 XIB 在 Storyboard中连接到扩展 UIView 的类 SingleEvent。

我想做以下事情:

1. 将 XIB 用作一种“蓝图”，并在我的 ScrollView 中多次加载相同的 View ；
2. 向任何实例传递一些数据；

这可能吗？

我试过这样加载XIB的内容:

 let customView = Bundle.main.loadNibNamed("SingleEvent", owner: self, options: nil)?.first as? SingleEvent

这样:

let customView = SingleEvent()

第一个导致应用程序崩溃，而第二个导致没有问题，但我看不到任何影响(它不加载任何东西)。

我最新的SingleEvent内容如下:

 import UIKit

    class SingleEvent: UIView {

        @IBOutlet weak var label:UILabel!
        @IBOutlet weak var imageView:UIImageView!

        override init(frame: CGRect) {
            super.init(frame: frame)

            loadViewFromNib()
        }

        required init?(coder aDecoder: NSCoder) {
            super.init(coder: aDecoder)

            loadViewFromNib()
        }

        func loadViewFromNib() -> UIView {
            let myView = Bundle.main.loadNibNamed("SingleEvent", owner: self, options: nil)?.first as! UIView
            return myView
        }
    }

提前致谢，感谢您的帮助:-)

Answer 1

有许多方法可以从 xibs 加载自定义 View (类)。您可能会发现此方法更容易一些。

首先，像这样创建你的 xib:

请注意，File's Owner 的类别是默认类别 (NSObject)。

相反，将您的自定义类分配给 xib 中的“根” View :

现在，我们的整个自定义 View 类如下所示:

class SingleEvent: UIView {

    @IBOutlet var topLabel: UILabel!
    @IBOutlet var middleLabel: UILabel!
    @IBOutlet var bottomLabel: UILabel!

    @IBOutlet var imageView: UIImageView!

}

并且，我们没有将 loadNibNamed(...) 放在我们的自定义类中，而是创建了一个 UIView 扩展:

extension UIView {
    class func fromNib<T: UIView>() -> T {
        return Bundle.main.loadNibNamed(String(describing: T.self), owner: nil, options: nil)![0] as! T
    }
}

要加载和使用我们的自定义类，我们可以这样做:

class FromXIBViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // create an instance of SingleEvent from its xib/nib
        let v = UIView.fromNib() as SingleEvent

        // we're going to use auto-layout & constraints
        v.translatesAutoresizingMaskIntoConstraints = false

        // set the text of the labels
        v.topLabel?.text    = "Top Label"
        v.middleLabel?.text = "Middle Label"
        v.bottomLabel?.text = "Bottom Label"

        // set the image
        v.imageView.image = UIImage(named: "myImage")

        // add the SingleEvent view
        view.addSubview(v)

        // constrain it 200 x 200, centered X & Y
        NSLayoutConstraint.activate([
            v.widthAnchor.constraint(equalToConstant: 200.0),
            v.heightAnchor.constraint(equalToConstant: 200.0),
            v.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            v.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            ])

    }

}

结果是:

还有...这是加载 10 个 SingleEvent View 实例并将它们添加到垂直 ScrollView 的示例:

class FromXIBViewController: UIViewController {

    var theScrollView: UIScrollView = {
        let v = UIScrollView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = .cyan
        return v
    }()

    var theStackView: UIStackView = {
        let v = UIStackView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.axis = .vertical
        v.alignment = .fill
        v.distribution = .fill
        v.spacing = 20.0
        return v
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        // add the scroll view to the view
        view.addSubview(theScrollView)

        // constrain it 40-pts on each side
        NSLayoutConstraint.activate([
            theScrollView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 40.0),
            theScrollView.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor, constant: -40.0),
            theScrollView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor, constant: 40.0),
            theScrollView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor, constant: -40.0),
            ])

        // add a stack view to the scroll view
        theScrollView.addSubview(theStackView)

        // constrain it 20-pts on each side
        NSLayoutConstraint.activate([
            theStackView.topAnchor.constraint(equalTo: theScrollView.topAnchor, constant: 20.0),
            theStackView.bottomAnchor.constraint(equalTo: theScrollView.bottomAnchor, constant: -20.0),
            theStackView.leadingAnchor.constraint(equalTo: theScrollView.leadingAnchor, constant: 20.0),
            theStackView.trailingAnchor.constraint(equalTo: theScrollView.trailingAnchor, constant: -20.0),

            // stackView width = scrollView width -40 (20-pts padding on left & right
            theStackView.widthAnchor.constraint(equalTo: theScrollView.widthAnchor, constant: -40.0),
            ])


        for i in 0..<10 {

            // create an instance of SingleEvent from its xib/nib
            let v = UIView.fromNib() as SingleEvent

            // we're going to use auto-layout & constraints
            v.translatesAutoresizingMaskIntoConstraints = false

            // set the text of the labels
            v.topLabel?.text    = "Top Label: \(i)"
            v.middleLabel?.text = "Middle Label: \(i)"
            v.bottomLabel?.text = "Bottom Label: \(i)"

            // set the image (assuming we have images named myImage0 thru myImage9
            v.imageView.image = UIImage(named: "myImage\(i)")

            theStackView.addArrangedSubview(v)

        }

    }

}

结果: