ios - UILabel 上的 instrictContentSize 在不同的实例中返回不同的值

Question

我正在使用 swift 3.0 开发一个项目，我在 UIStoryBoard 中有三个 numberOFLines 设置为 6 的 UILabel。在标签下方，我放置了三个 UIButton，它们用作“查看更多”选项。有时我的代码工作正常，如果我截断的标签显示“查看更多”按钮，一旦单击它会显示全部内容，而有时即使 UILabel 内容被截断它仍然不显示“查看更多”按钮所以我'我无法看到全部内容。我在代码中缺少什么，帮助将不胜感激。

   import UIKit

class MP3ViewController: UIViewController,UITableViewDataSource,UITableViewDelegate {

    @IBOutlet var descriptionSeeMoreBtn: UIButton!

    @IBOutlet var howToUseSeeMoreBtn: UIButton!

    @IBOutlet var cautionsSeeMreBtn: UIButton!
    var seeMoreIsShowing =  false
    @IBOutlet var cautionsContentLbl: UILabel!
    @IBOutlet var howToUseContentLbl: UILabel!
    @IBOutlet var descriptionContentLbl: UILabel!

   override func viewDidLoad() {
        self.descriptionContentLbl.sizeToFit()
        self.howToUseContentLbl.sizeToFit()
        self.cautionsContentLbl.sizeToFit()
        getItButton.layer.cornerRadius = 5
        activityIndicator.startAnimating()
        let mediaID = mediaDetails?["entity_key"] as! String
        let url = URL(string: Config.MP3_LIST + "?mediaId=\(mediaID)")
        let task = URLSession.shared.dataTask(with: url!, completionHandler: { (data, response, error) in

            if(error != nil){
                print(error!);
                DispatchQueue.main.sync(execute: {
                    self.activityIndicator.stopAnimating()
                })
            }
            else{
                do{
                    if let urlContent = data {
                        let  serverResponseData = try (JSONSerialization.jsonObject(with: urlContent, options: JSONSerialization.ReadingOptions.mutableContainers)) as! NSDictionary
                        if(serverResponseData["error"] == nil){
                            self.mediaDetails = serverResponseData
                            print("Media :",self.mediaDetails!)
                            self.mediaList = (self.mediaDetails?["trackList"]as? NSArray)!

                            DispatchQueue.main.sync(execute: {

                                self.descriptionContentLbl.text =  self.mediaDetails?["description"] as? String ?? "description...."
                                self.howToUseContentLbl.text =  self.mediaDetails?["howToUse"] as? String ?? "How to use......."
                                self.cautionsContentLbl.text =  self.mediaDetails?["cautions"] as? String ?? "cautions...."
                                let track = ((self.mediaDetails?["trackList"] as! NSArray)[0]) as! NSDictionary
                                self.activityIndicator.stopAnimating()
                            })
                        }
                    }
                }
                catch {
                    print("Error In Json De-serialization")
                }
                DispatchQueue.main.sync(execute: {
                    self.activityIndicator.stopAnimating()
                })
            }
        })
        task.resume();

    }

    override func viewDidAppear(_ animated: Bool) {
        loadTheInitialLabelText()
        self.tableView.tableFooterView = UIView(frame: .zero)
    }

    @IBAction func descriptionSeeMoreButtonPressed(_ sender: Any) {
        if (seeMoreIsShowing) {
            self.descriptionContentLbl.numberOfLines = 6
            self.descriptionSeeMoreBtn.setTitle("see more", for: .normal)
        }else {
            self.descriptionContentLbl.numberOfLines = 0
            self.descriptionSeeMoreBtn.setTitle("show less", for: .normal)
        }
        seeMoreIsShowing = !seeMoreIsShowing
    }
    @IBAction func howToUSeSeeMoreButtonPressed(_ sender: Any) {
        if (seeMoreIsShowing) {
            self.howToUseContentLbl.numberOfLines = 6
            self.howToUseSeeMoreBtn.setTitle("see more", for: .normal)
        }else {
            self.howToUseContentLbl.numberOfLines = 0
            self.howToUseSeeMoreBtn.setTitle("show less", for: .normal)
        }
        seeMoreIsShowing = !seeMoreIsShowing
    }


    @IBAction func cautionsSeeMoreButtonPressed(_ sender: Any) {
        if (seeMoreIsShowing) {
            self.cautionsContentLbl.numberOfLines = 6
            self.cautionsSeeMreBtn.setTitle("see more", for: .normal)
        }else {
            self.cautionsContentLbl.numberOfLines = 0
            self.cautionsSeeMreBtn.setTitle("show less", for: .normal)
        }
        seeMoreIsShowing = !seeMoreIsShowing
    }

func loadTheInitialLabelText() {
        let DescriptionTextheight = self.descriptionContentLbl.text?.height(withConstrainedWidth: self.descriptionContentLbl.frame.width, font: self.descriptionContentLbl.font)
        if self.descriptionContentLbl.intrinsicContentSize.height < DescriptionTextheight! {
            self.descriptionSeeMoreBtn.isHidden = false
        }else{
            self.descriptionSeeMoreBtn.isHidden = true
        }

        let howToUseTextheight = self.howToUseContentLbl.text?.height(withConstrainedWidth: self.howToUseContentLbl.frame.width, font: self.howToUseContentLbl.font)
        if self.howToUseContentLbl.intrinsicContentSize.height < howToUseTextheight! {
            self.howToUseSeeMoreBtn.isHidden = false
        }else{
            self.howToUseSeeMoreBtn.isHidden = true
        }

        let cautionsTextheight = self.cautionsContentLbl.text?.height(withConstrainedWidth: self.cautionsContentLbl.frame.width, font: self.cautionsContentLbl.font)
        if self.cautionsContentLbl.intrinsicContentSize.height < cautionsTextheight! {
            self.cautionsSeeMreBtn.isHidden = false
        }else{
            self.cautionsSeeMreBtn.isHidden = true
        }

    }

}
extension String {

    func height(withConstrainedWidth width: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)

        return boundingBox.height
    }
}

Answer 1

你在设置它们的文本值之前调整你的标签大小，在设置它们的值之后调整大小。但这并不能解决问题。

我相信可能发生的情况是您的网络服务返回时间太长。因此，当您的网络服务正在等待时，您的程序的其余部分将继续执行。

因此，您最终会比较空标签并获取它们的高度，然后获取这些标签的固有内容大小。固有大小是非文本填充标签的大小，它小于您的函数为该标签计算的任何高度。这最终会隐藏您的按钮。

之后，URLSession 会为您提供数据并设置标签的文本值，但高度计算已经发生。

您可以尝试的快速解决方法是在设置标签文本后，在 ViewDidLoad URLSession 处理程序中调用 LoadInitialText()。