NSTextAttachment图像对齐

Question

我正在遵循@Duncan Groenewald的这个很酷的教程Implementing Rich Text with Images on OS X and iOS，并且能够在我的UITextView中显示图像。然而，这些图像并不像我希望的那样居中。请参见图像

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如你所见，我希望我的图像在X轴上居中。

我尝试在-attachmentBoundsForTextContainer:proposedLineFragment:glyphPosition:characterIndex中使用适当的值返回rect，但没有任何帮助。

我还尝试为NSTextAttachment属性字符串设置NSKernAttributeName。但它所做的一切只是隐藏了一些图像。

Answer 1

尝试在附件中设置居中对齐的段落样式。

如果您的图像作为附件嵌入在属性字符串中，则可以通过枚举属性字符串的附件属性来访问它们。例如：

    attributedContent.enumerateAttribute(NSAttachmentAttributeName, inRange: NSRange(location: 0, length: attributedContent.length), options: nil) { (attribute, range, stop) -> Void in
        if let attachment = attribute as? NSTextAttachment {

            // this example assumes you want to center all attachments. You can provide additional logic here. For example, check for attachment.image.

            let paragraphStyle = NSMutableParagraphStyle()
            paragraphStyle.alignment = .Center
            attributedContent.addAttribute(NSParagraphStyleAttributeName, value: paragraphStyle, range: range)
        }
    }

Answer 2

这是使用扩展的Swift 3.1

extension NSMutableAttributedString {

    func setAttachmentsAlignment(_ alignment: NSTextAlignment) {
        self.enumerateAttribute(NSAttachmentAttributeName, in: NSRange(location: 0, length: self.length), options: .longestEffectiveRangeNotRequired) { (attribute, range, stop) -> Void in
            if attribute is NSTextAttachment {
                let paragraphStyle = NSMutableParagraphStyle()
                paragraphStyle.alignment = alignment
                self.addAttribute(NSParagraphStyleAttributeName, value: paragraphStyle, range: range)
            }
        }
    }

}

这样，您就可以轻松地对属性字符串上的附件应用对齐方式：

let attributeString = NSMutableAttributedString(string: "")
// add attachments
attributeString.setAttachmentsAlignment(.center) 

Answer 3

下面是设置NSTextAttachment图像对齐方式的另一种方法。希望这也能帮助那些在这方面苦苦挣扎的人。我在func tableView(_ tableView: UITableView，cellForRowAt indexPath: IndexPath) -> UITableViewCell中使用以下代码

var buttonText = "My Button";

let align = NSMutableParagraphStyle();
align.alignment = NSTextAlignment.center;
align.firstLineHeadIndent = 10.0;
align.headIndent = 10.0;
align.tailIndent = -10.0;

let para = NSMutableAttributedString();

// top padding
para.append(NSAttributedString(string: "\n", attributes: [NSParagraphStyleAttributeName: align, NSFontAttributeName: UIFont(name: "Helvetica", size: 10.0)!, NSForegroundColorAttributeName: UIColor.white]));

// image
let img = NSTextAttachment();
img.image = UIImage(named: "MyIcon");
img.bounds = CGRect(x: 0, y: UIFont(name: "Helvetica", size: 18.0)!.descender, width: img.image!.size.width, height: img.image!.size.height);
let nas = NSAttributedString(attachment: img).mutableCopy() as! NSMutableAttributedString;
nas.addAttribute(NSParagraphStyleAttributeName, value: align, range: NSRange(location: 0, length: nas.length));
para.append(nas);

// space to text
buttonText = " " + buttonText;

// text
para.append(NSAttributedString(
    string: buttonText,
    attributes: [NSParagraphStyleAttributeName: align, NSFontAttributeName: UIFont(name: "Helvetica", size: 18.0)!, NSForegroundColorAttributeName: UIColor.black]));

// bottom padding
para.append(NSAttributedString(string: "\n", attributes: [NSParagraphStyleAttributeName: align, NSFontAttributeName: UIFont(name: "Helvetica", size: 10.0)!, NSForegroundColorAttributeName: UIColor.white]));

// set cell label
let label = cell.textLabel!;
label.numberOfLines = 0;
label.layer.borderWidth = 0;
label.layer.masksToBounds = false;
label.backgroundColor = UIColor.clear;
label.layer.backgroundColor = UIColor.green;
label.attributedText = para;