swift - 如何为自定义字体声明 NSAttributedStringKey.font？

Question

我想计算文本的高度以获得 Collection View 单元格的估计高度。我在 collectionViewLayout 函数中使用了以下代码；

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    if let messageText = messages[indexPath.row]?.text {

        let size = CGSize(width: view.frame.width, height: 1000)
        let options = NSStringDrawingOptions.usesFontLeading.union(.usesLineFragmentOrigin)
        let estimatedFrame = NSString(string: messageText).boundingRect(with: size, options: options, attributes: [NSAttributedStringKey.font: UIFont.systemFont(ofSize: 17)], context: nil)
        return CGSize(width: view.frame.width, height: estimatedFrame.height + 20)
    }

    return CGSize(width: view.frame.width, height: 100)
}

这适用于系统字体，但不适用于我项目中的自定义字体。问题是 estimatedFrame 不等于使用系统字体的结果。我认为问题在于选项的参数:attributes。有没有像 UIFont.systemFont(ofSize: 17) 这样的自定义字体的方法？

Answer 1

如果我没看错你的问题，你想要:

UIFont(name: "yourCustomFontNameString", size: 17)

所以:

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {

    if let messageText = messages[indexPath.row]?.text {

        let size = CGSize(width: view.frame.width, height: 1000)
        let options = NSStringDrawingOptions.usesFontLeading.union(.usesLineFragmentOrigin)
        let estimatedFrame = NSString(string: messageText).boundingRect(with: size, options: options, attributes: [NSAttributedStringKey.font: UIFont(name: "yourCustomFontNameString", size: 17)], context: nil)
        return CGSize(width: view.frame.width, height: estimatedFrame.height + 20)
    }

    return CGSize(width: view.frame.width, height: 100)
}