ios - 数据更改后刷新 View

Question

我正在尝试进行实时聊天，进展顺利，但我遇到了问题。

我已经向navigationController 添加了一个 subview 而不是标题。我在这个 View 中有一个头像、用户全名和状态，就像 Whatsapp 一样。我从推送服务获得了用户在线字符串，我想将其显示在用户全名(例如 Whatsapp)的 subview 底部。当我从 func onPresenceChanged(stateChange method ) 获取在线字符串时，如何刷新 View ？

我添加了 self.navbar.setNeedsDisplay() 但它不起作用。

ChatViewController.swift(我将其裁剪以便快速查看)

class ChatViewController: UIViewController, UITextFieldDelegate, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, PCRoomDelegate {

var navbarView = UIView()
var navbarAvatar = UIImageView()
var navbar = UILabel()
var statusString = [String]()
var usernameString = [String]()

override func viewDidLoad() {
    super.viewDidLoad()


    self.navbarView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: UIScreen.main.bounds.width / 1.4, height: 44.0))
    self.navbarView.backgroundColor = UIColor.clear

    self.navbar = UILabel(frame: CGRect(x: 44.0, y: 0.0, width: UIScreen.main.bounds.width / 1.4 - 44, height: 44.0))
    self.navbar.backgroundColor = UIColor.clear
    self.navbar.numberOfLines = 2
    self.navbar.textAlignment = NSTextAlignment.left

    let bodyText = NSMutableAttributedString(string: "Halil İbrahim YÜCE", attributes: [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 16, weight: .bold)])

    usernameString.append("\n@" + "halilyc")

    bodyText.append(NSAttributedString(string: usernameString.last!, attributes: [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 13), NSAttributedString.Key.foregroundColor : UIColor.gray]))

    self.navbar.attributedText = bodyText
    self.navbarView.addSubview(navbar)
    self.navigationItem.titleView = self.navbarView

}


func onPresenceChanged(
    stateChange: PCPresenceStateChange,
    user: PCUser
    ) {
    print("User \(user.displayName)'s presence changed to \(stateChange.current.rawValue)")
    self.statusString.append(stateChange.current.rawValue)

    self.navbar.setNeedsDisplay()

    if statusString.count != 0 {
     self.usernameString.append("\n@" + statusString.last!)
    }

}

}

Answer 1

将字符串变量分配给 UILabel 的 attributedText 属性不会在该字符串和标签之间创建绑定(bind)；如果您想在 UI 中看到更新的值，则需要更新 attributedText。另外，UI更新必须在主线程上执行；来自网络的更新将在后台线程上传递。

最后，我认为没有必要保留一系列状态，您只需要最新的状态。

您可以重构以创建一个计算变量，为导航栏提供当前用户状态文本。

不清楚您打算如何显示显示名称、用户名和状态(有 3 个内容，但只有 2 行)。我刚刚将其设置为三行，您可以根据需要进行调整。

class ChatViewController: UIViewController, UITextFieldDelegate,  UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, PCRoomDelegate {

var navbarView: UIView!
var navbarAvatar: UIImageView!
var navbar: UILabel!
var status: String? {
    didSet {
        self.updateNavText()
    }

var username: String? {
    didSet {
        self.updateNavText()
    }

var displayName: String?
    didSet {
        self.updateNavText()
    }

var statusText: NSAttributedString {
    let text = NSMutableAttributedString(string: displayName ?? "", attributes: [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 16, weight: .bold)])
    if let username = self.username {
        text.append("\n@\(username)")
    }
    if let status = self.status {
        text.append("\n\(status)")
    }
    return text
}

override func viewDidLoad() {
    super.viewDidLoad()    
    self.navbarView = UIView(frame: CGRect(x: 0.0, y: 0.0, width: UIScreen.main.bounds.width / 1.4, height: 44.0))
    self.navbarView.backgroundColor = UIColor.clear

    self.navbar = UILabel(frame: CGRect(x: 44.0, y: 0.0, width: UIScreen.main.bounds.width / 1.4 - 44, height: 44.0))
    self.navbar.backgroundColor = UIColor.clear
    self.navbar.numberOfLines = 2
    self.navbar.textAlignment = NSTextAlignment.left

    let bodyText = NSMutableAttributedString(string: "Halil İbrahim YÜCE", attributes: [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 16, weight: .bold)])

    self.updateNavText()
    self.navbarView.addSubview(navbar)
    self.navigationItem.titleView = self.navbarView

}


func onPresenceChanged(
    stateChange: PCPresenceStateChange,
    user: PCUser
    ) {
    print("User \(user.displayName)'s presence changed to \(stateChange.current.rawValue)")

    DispatchQueue.main.async {
          self.status = stateChange.current.rawValue
    }
}

func updateNavText() {
    self.navbar.attributedText = self.statusText
}