ios - 检查 UILabel 中的截断 - iOS、Swift

Question

我正在快速开发一个应用程序。目前，我正在处理带有自定义单元格的 TableView 的填充，请参阅 screenshot .但是，现在我设置了文本，标题正好是 2 行，摘要正好是 3 行。通过这样做，文本有时会被截断。现在，我想设置标题中文本的优先级，以便如果标题在 2 行长时被截断，我将其扩展为 3 行并使摘要只有 2 行。我尝试使用自动布局来执行此操作，但失败了。现在我根据 this 尝试了以下方法和 this , 但下面的函数似乎也没有准确确定文本是否被截断。

    func isTruncated(label:UILabel) -> Bool {
    let context = NSStringDrawingContext()
    let text : NSAttributedString = NSAttributedString(string: label.text!, attributes: [NSFontAttributeName : label.font])

    let labelSize : CGSize = CGSize(width: label.frame.width, height: CGFloat.max)


    let options : NSStringDrawingOptions = unsafeBitCast(NSStringDrawingOptions.UsesLineFragmentOrigin.rawValue | NSStringDrawingOptions.UsesFontLeading.rawValue, NSStringDrawingOptions.self)

    let labelRect : CGRect = text.boundingRectWithSize(labelSize, options: options, context: context)

    if Float(labelRect.height/label.font.lineHeight) > Float(label.numberOfLines) {
        return true
    } else {
        return false
    }
}

有人可以帮忙吗？我怎样才能改变我的功能来完成这项工作？或者应该使用不同的自动布局约束以及如何工作？非常感谢!

---

编辑:这是我当前的代码。一些自动布局是在 Storyboard中完成的，但是更改自动布局是在代码中完成的。 导入 UIKit

class FeedTableViewCell: UITableViewCell {

var thumbnailImage = UIImageView()

@IBOutlet var titleText: UILabel!

@IBOutlet var summaryText: UILabel!

@IBOutlet var sourceAndDateText: UILabel!

var imgTitleConst = NSLayoutConstraint()
var imgSummaryConst = NSLayoutConstraint()
var imgDetailConst = NSLayoutConstraint()

var titleConst = NSLayoutConstraint()
var summaryConst = NSLayoutConstraint()
var detailConst = NSLayoutConstraint()

var titleHeightConst = NSLayoutConstraint()
var summaryHeightConst = NSLayoutConstraint()


var imageRemoved = false
var titleConstAdd = false
override func awakeFromNib() {
    super.awakeFromNib()
    thumbnailImage.clipsToBounds = true
    summaryText.clipsToBounds = true
    titleText.clipsToBounds = true
    sourceAndDateText.clipsToBounds = true
    addImage()

}

   func removeImage() {
    if let viewToRemove = self.viewWithTag(123) {
        imageRemoved = true
         viewToRemove.removeFromSuperview()
          self.contentView.removeConstraints([imgTitleConst,  imgSummaryConst, imgDetailConst])
        titleConst = NSLayoutConstraint(item: self.titleText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.Left, multiplier: 1, constant: 14)

        summaryConst = NSLayoutConstraint(item: summaryText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.Left, multiplier: 1, constant: 14)

        detailConst = NSLayoutConstraint(item: sourceAndDateText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.Left, multiplier: 1, constant: 14)

        self.contentView.addConstraints([titleConst, detailConst, summaryConst])
        setNumberOfLines()
        self.contentView.layoutSubviews()
    }


}

func addImage() {
    thumbnailImage.tag = 123
    thumbnailImage.image = UIImage(named: "placeholder")
    thumbnailImage.frame = CGRectMake(14, 12, 100, 100)
    thumbnailImage.contentMode = UIViewContentMode.ScaleAspectFill
    thumbnailImage.clipsToBounds = true
    self.contentView.addSubview(thumbnailImage)

    if imageRemoved {
        self.contentView.removeConstraints([titleConst, summaryConst, detailConst])
    }


    var widthConst = NSLayoutConstraint(item: thumbnailImage, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 100)
    var heightConst = NSLayoutConstraint(item: thumbnailImage, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 100)
    var leftConst = NSLayoutConstraint(item: thumbnailImage, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.Left, multiplier: 1, constant: 14)
    var topConst = NSLayoutConstraint(item: thumbnailImage, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self.contentView, attribute: NSLayoutAttribute.Top, multiplier: 1, constant: 12)



      imgTitleConst = NSLayoutConstraint(item: self.titleText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.thumbnailImage, attribute: NSLayoutAttribute.Right, multiplier: 1, constant: 8)

     imgSummaryConst = NSLayoutConstraint(item: summaryText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.thumbnailImage, attribute: NSLayoutAttribute.Right, multiplier: 1, constant: 8)

     imgDetailConst = NSLayoutConstraint(item: sourceAndDateText, attribute: NSLayoutAttribute.Left, relatedBy: NSLayoutRelation.Equal, toItem: self.thumbnailImage, attribute: NSLayoutAttribute.Right, multiplier: 1, constant: 8)


    self.contentView.addConstraints([widthConst, heightConst, leftConst, topConst, imgTitleConst, imgSummaryConst, imgDetailConst])
    setNumberOfLines()
    self.contentView.layoutSubviews()

}




override func setSelected(selected: Bool, animated: Bool) {
    super.setSelected(selected, animated: animated)

    // Configure the view for the selected state
}

func setNumberOfLines() {

    if titleConstAdd {
        self.contentView.removeConstraints([titleHeightConst, summaryHeightConst])
    }
    if titleText.numberOfLines == 3 {
        titleText.numberOfLines = 2
    }
    if countLabelLines(titleText) > 2 {
        titleText.numberOfLines = 3
        summaryText.numberOfLines = 2
        println("adjusting label heigh to be taller")
         titleHeightConst = NSLayoutConstraint(item: titleText, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 51)
        summaryHeightConst = NSLayoutConstraint(item: summaryText, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 32)
        self.contentView.addConstraints([titleHeightConst, summaryHeightConst])
    } else {
        titleText.numberOfLines = 2
        summaryText.numberOfLines = 3

         titleHeightConst = NSLayoutConstraint(item: titleText, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 36)
            summaryHeightConst = NSLayoutConstraint(item: summaryText, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: 47)
        self.contentView.addConstraints([titleHeightConst, summaryHeightConst])
    }

    titleConstAdd = true


 }
 }


func countLabelLines(label:UILabel)->Int{

if let text = label.text{
    // cast text to NSString so we can use sizeWithAttributes
    var myText = text as NSString

    //Set attributes
    var attributes = [NSFontAttributeName :  UIFont.boldSystemFontOfSize(14)]

    //Calculate the size of your UILabel by using the systemfont and the paragraph we created before. Edit the font and replace it with yours if you use another

    var labelSize = myText.boundingRectWithSize(CGSizeMake(label.bounds.width, CGFloat.max), options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: attributes, context: nil)

    //Now we return the amount of lines using the ceil method
    var lines = ceil(CGFloat(labelSize.height) / label.font.lineHeight)
    println(labelSize.height)
    println("\(lines)")
    return Int(lines)
}

return 0

}

Answer 1

您可以使用 NSString 中的 sizeWithAttributes 方法来获取 UILabel 的行数。您必须先将标签文本转换为 NSString 才能使用此方法:

func countLabelLines(label:UILabel)->Int{

    if let text = label.text{
        // cast text to NSString so we can use sizeWithAttributes
        var myText = text as NSString
        //A Paragraph that we use to set the lineBreakMode.
        var paragraph = NSMutableParagraphStyle()
        //Set the lineBreakMode to wordWrapping
        paragraph.lineBreakMode = NSLineBreakMode.ByWordWrapping

        //Calculate the size of your UILabel by using the systemfont and the paragraph we created before. Edit the font and replace it with yours if you use another
        var labelSize = myText.sizeWithAttributes([NSFontAttributeName : UIFont.systemFontOfSize(17), NSParagraphStyleAttributeName : paragraph.copy()])

        //Now we return the amount of lines using the ceil method
        var lines = ceil(CGFloat(size.height) / label.font.lineHeight)
        return Int(lines)
    }

    return 0

}

编辑

如果此方法对您不起作用，因为您的标签没有固定宽度，您可以使用 boundingRectWithSize 获取标签的大小并将其与 ceil< 一起使用 方法。

func countLabelLines(label:UILabel)->Int{

    if let text = label.text{
        // cast text to NSString so we can use sizeWithAttributes
        var myText = text as NSString

        //Set attributes
        var attributes = [NSFontAttributeName : UIFont.systemFontOfSize(UIFont.systemFontSize())]

        //Calculate the size of your UILabel by using the systemfont and the paragraph we created before. Edit the font and replace it with yours if you use another
        var labelSize = myText.boundingRectWithSize(CGSizeMake(label.bounds.width, CGFloat.max), options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: attributes, context: nil)

        //Now we return the amount of lines using the ceil method
        var lines = ceil(CGFloat(labelSize.height) / label.font.lineHeight)
        return Int(lines)
    }

    return 0

}