ios - UIView Controller 实例化

Question

我正在尝试以编程方式实例化 UIView 和 UIViewController，但在显示我的任何标签、文本字段等时遇到问题。

我的 View Controller 看起来像这样:

import UIKit

class AdminNewsController: UIViewController {

var adminNewsView : AdminNewsView!


let newsTitleMarker : UILabel = {
    let label = UILabel()
    label.text = "Title: "
    label.font.withSize(AMA_Constants.FontSizes.HeadingSize)
    label.textColor = AMA_Constants.FontColor.LabelMarkingColor
    label.textAlignment = .center
    label.translatesAutoresizingMaskIntoConstraints = false
    return label
}()

let newsTitleTextEdit : UITextField = {
    let textEdit = UITextField()
    textEdit.text = "Text View"
    textEdit.textColor = AMA_Constants.FontColor.LabelMarkingColor
    textEdit.textAlignment = .center
    textEdit.translatesAutoresizingMaskIntoConstraints = false
    return textEdit
}()

override func viewDidLoad() {
    super.viewDidLoad()

    adminNewsView = AdminNewsView()
    adminNewsView.backgroundColor = AMA_Constants.AppPrimaryColor
    self.view.addSubview(adminNewsView)

    setupViews()

    navigationController?.navigationBar.barStyle = .black
    navigationController?.navigationBar.tintColor = AMA_Constants.AppSecondaryColor
    self.navigationItem.title = "Admin - News"

}


func setupViews() {

    adminNewsView.addSubview(newsTitleMarker)
    adminNewsView.addSubview(newsTitleTextEdit)


    adminNewsView.translatesAutoresizingMaskIntoConstraints = false
    adminNewsView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
    adminNewsView.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
    adminNewsView.widthAnchor.constraint(equalTo: self.view.widthAnchor).isActive = true
    adminNewsView.heightAnchor.constraint(equalTo: self.view.heightAnchor).isActive = true

    newsTitleMarker.anchor(adminNewsView.topAnchor, left: adminNewsView.leftAnchor, bottom: nil, right: nil, topConstant: AMA_Constants.Alignment_Space.paddingVerticalExternal, leftConstant: AMA_Constants.Alignment_Space.paddingHorizontalExternal, bottomConstant: 0, rightConstant: 0, widthConstant: 0, heightConstant: 0)



    newsTitleTextEdit.anchor(newsTitleMarker.topAnchor, left: newsTitleMarker.rightAnchor, bottom: nil, right: adminNewsView.rightAnchor, topConstant: 0, leftConstant: AMA_Constants.Alignment_Space.paddingHorizontalInternal, bottomConstant: 0, rightConstant: AMA_Constants.Alignment_Space.paddingHorizontalExternal, widthConstant: 0, heightConstant: 0)

}}

但在模拟器中， View 是正确的(白色)颜色，但没有标签或 UITextView。

问题:

1. 我是否正确实例化并创建了 View adminNewsView？
2. 为什么不生成标签和 UITextView？
3. 没有完全理解 IOS 上的 MVC，我的 adminNewsView 类应该写些什么？我以为我应该在其中包含我的 setupViews() 函数，但事实并非如此。

Answer 1

我对您的代码有一些问题，所以我以一种我认为有助于更好地为您说明编程 View Controller 的过程的方式重构它。其中一个问题是您从未创建 View Controller 的 View ，这对于编程 View Controller 是强制性的。

我强烈建议像书一样编写代码——从左到右，从上到下。首先声明所有需要成为实例属性的属性，然后调用所有生命周期事件(我不会在生命周期方法中放置任何不是方法调用的代码，因为它读起来容易得多)，然后编写那些方法出来了。

import UIKit

class AdminNewsController: UIViewController {


    // MARK: Properties


    let adminNewsView = AdminNewsView()
    let newsTitleMarker = UILabel()
    let newsTitleTextEdit = UITextField()


    // MARK: Lifecycle


    override func loadView() {

        // do NOT call super.loadView() when programmatically creating a
        // view controller

        // do all of your basic setup here in loadView

        setView()
        addAdminNewsView()
        addNewsTitleMarker()
        addNewsTitleTextEdit()

    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // do call super.viewDidLoad() however
        // do post-basic setup stuff here in viewDidLoad
        // viewDidLoad is called after the entire view controller has been
        // loaded into memory so consider that

    }


    // other lifecycle events that come after viewDidLoad where you can do some
    // last-second touches include viewDidLayoutSubviews(), viewDidAppear(), etc.


    deinit {

        // do any cleanup here like deactivating timers, removing observers, etc.

    }


    // MARK: Methods


    func setView() {

        view = UIView()
        view.frame = UIScreen.main.bounds
        view.backgroundColor = UIColor.white

    }


    func addAdminNewsView() {

        adminNewsView.backgroundColor = AMA_Constants.AppPrimaryColor
        adminNewsView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(adminNewsView)
        adminNewsView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        adminNewsView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        adminNewsView.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
        adminNewsView.heightAnchor.constraint(equalTo: view.heightAnchor).isActive = true

    }


    func addNewsTitleMarker() {

        newsTitleMarker.text = "Title: "
        newsTitleMarker.font.withSize(AMA_Constants.FontSizes.HeadingSize)
        newsTitleMarker.textColor = AMA_Constants.FontColor.LabelMarkingColor
        newsTitleMarker.textAlignment = .center
        newsTitleMarker.translatesAutoresizingMaskIntoConstraints = false
        adminNewsView.addSubview(newsTitleMarker)

        // add newsTitleMarker constraints

    }


    func addNewsTitleTextEdit() {

        newsTitleTextEdit.text = "Text View"
        newsTitleTextEdit.textColor = AMA_Constants.FontColor.LabelMarkingColor
        newsTitleTextEdit.textAlignment = .center
        newsTitleTextEdit.translatesAutoresizingMaskIntoConstraints = false
        adminNewsView.addSubview(newsTitleTextEdit)

        // add newsTitleTextEdit constraints

    }


}

既然你问了，下面是子类化的 UIView 的样子。请注意不同的生命周期方法。

class SomeView: UIView {


    // MARK: Properties


    private let itemBanner = UIImageView()
    private let itemLabel = UILabel()
    var itemName: String
    var itemPicture: UIImage


    // MARK: Lifecycle


    init(name: String, picture: UIImage) {

        self.itemName = name
        self.itemPicture = picture
        super.init(frame: CGRect.zero)
        config()
        addItemBanner()
        addItemLabel()

    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    override func updateConstraints() {
        super.updateConstraints()

        setConstraints()

    }


    override func layoutSubviews() {
        super.layoutSubviews()

        // this can be a very useful method when subclassing views

    }


    // MARK: Methods


    private func config() {

        isOpaque = false

    }


    private func addItemBanner() {

        itemBanner.image = itemPicture
        itemBanner.clipsToBounds = true
        itemBanner.contentMode = .scaleAspectFill
        itemBanner.translatesAutoresizingMaskIntoConstraints = false
        addSubview(itemBanner)

    }


    private func addItemLabel() {

        itemLabel.text = itemName
        itemLabel.textAlignment = .left
        itemLabel.numberOfLines = 3
        itemLabel.lineBreakMode = .byTruncatingTail
        itemLabel.font = UIFont.bigTitle
        itemLabel.translatesAutoresizingMaskIntoConstraints = false
        itemBanner.addSubview(itemLabel)

    }


    private func setConstraints() {

        // banner
        itemBanner.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
        itemBanner.topAnchor.constraint(equalTo: topAnchor).isActive = true
        itemBanner.widthAnchor.constraint(equalTo: widthAnchor).isActive = true
        itemBanner.heightAnchor.constraint(equalToConstant: 96).isActive = true
        itemBanner.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true

        // label
        itemLabel.centerXAnchor.constraint(equalTo: itemBanner.centerXAnchor).isActive = true
        itemLabel.centerYAnchor.constraint(equalTo: itemBanner.centerYAnchor).isActive = true
        itemLabel.widthAnchor.constraint(equalTo: itemBanner.widthAnchor, constant: -32).isActive = true
        itemLabel.sizeToFit()

    }


}