如何获取适合固定大小文本视图的属性文本范围

Question

我正在尝试确定适合恒定大小的属性文本的数量 textview.I 已尝试使用 CTFrameSetter，但我认为这仅在我们已经知道要添加的文本时才有用. 到目前为止我已经试过了

 func numberOfCharactersThatFitTextView() -> Int {
        let fontRef = CTFontCreateWithName(font!.fontName as CFString, font!.pointSize, nil)
        let attributes = [kCTFontAttributeName : fontRef]
    let attributedString = NSAttributedString(string: text!, attributes: attributes as [NSAttributedString.Key : Any])
        let frameSetterRef = CTFramesetterCreateWithAttributedString(attributedString as CFAttributedString)

        var characterFitRange: CFRange = CFRange()

        CTFramesetterSuggestFrameSizeWithConstraints(frameSetterRef, CFRangeMake(0, 0), nil, CGSize(width: bounds.size.width, height: bounds.size.height), &characterFitRange)
        return Int(characterFitRange.length)

    }

Answer 1

编辑

有时候，我会想太多...

如果您只想获得适合的最大行数，您可以使用字体的 .lineHeight 属性:

    // the height of your text view
    let h: CGFloat = 160.0

    // whatever your font is
    let font: UIFont = .systemFont(ofSize: 24.0)
    
    let maxLines: Int = Int(floor(h / font.lineHeight))
    
    print("Max Number of Lines:", maxLines)

原答案

如果您想要适合给定 textView 高度的行数，您可以这样做...

首先，一个方便的扩展：

extension NSAttributedString {
    
    func height(containerWidth: CGFloat) -> CGFloat {
        
        let rect = self.boundingRect(with: CGSize.init(width: containerWidth, height: CGFloat.greatestFiniteMagnitude),
                                     options: [.usesLineFragmentOrigin, .usesFontLeading],
                                     context: nil)
        return ceil(rect.size.height)
    }
    
    func width(containerHeight: CGFloat) -> CGFloat {
        
        let rect = self.boundingRect(with: CGSize.init(width: CGFloat.greatestFiniteMagnitude, height: containerHeight),
                                     options: [.usesLineFragmentOrigin, .usesFontLeading],
                                     context: nil)
        return ceil(rect.size.width)
    }
    
}

然后，使用这个函数：

func numberOfLinesThatFit(inHeight height: CGFloat, withFont font: UIFont) -> Int {

    let attributes: [NSAttributedString.Key : Any] = [.font : font]
    
    var n: Int = 0
    
    var str: String = "A"
    
    var attStr: NSAttributedString = NSAttributedString(string: str, attributes: attributes)
    
    // width just needs to be greater than one character width
    var h: CGFloat = attStr.height(containerWidth: 200.0)
    
    while h < height {
        n += 1
        str += "\nA"
        attStr = NSAttributedString(string: str, attributes: attributes)
        h = attStr.height(containerWidth: 200.0)
    }
    
    return n

}

并这样称呼它：

    // whatever your font is
    let font: UIFont = .systemFont(ofSize: 24.0)
    
    // the height of your text view
    let h: CGFloat = 160.0
    
    let maxLines: Int = numberOfLinesThatFit(inHeight: h, withFont: font)
    
    print("max lines:", maxLines)

如何获取适合固定大小文本视图的属性文本范围

How to get the range of Attributed text that can fit in a constant size textview

textview

ios

swift