我想将NSTextAttachment图像附加到我的属性字符串并使其垂直居中。
我使用以下代码来创建我的字符串：
NSMutableAttributedString *str = [[NSMutableAttributedString alloc] initWithString:DDLocalizedString(@"title.upcomingHotspots") attributes:attrs];
NSTextAttachment *attachment = [[NSTextAttachment alloc] init];
attachment.image = [[UIImage imageNamed:@"help.png"] imageScaledToFitSize:CGSizeMake(14.f, 14.f)];
cell.textLabel.attributedText = [str copy];
但是，图像似乎与单元格的顶部对齐textLabel。
如何更改绘制附件的矩形？
您可以使用字体的 capHeight。
Objective-C
NSTextAttachment *icon = [[NSTextAttachment alloc] init];
UIImage *iconImage = [UIImage imageNamed:@"icon.png"];
[icon setBounds:CGRectMake(0, roundf(titleFont.capHeight - iconImage.size.height)/2.f, iconImage.size.width, iconImage.size.height)];
[icon setImage:iconImage];
NSAttributedString *iconString = [NSAttributedString attributedStringWithAttachment:icon];
[titleText appendAttributedString:iconString];
迅速
let iconImage = UIImage(named: "icon.png")!
var icon = NSTextAttachment()
icon.bounds = CGRect(x: 0, y: (titleFont.capHeight - iconImage.size.height).rounded() / 2, width: iconImage.size.width, height: iconImage.size.height)
icon.image = iconImage
let iconString = NSAttributedString(attachment: icon)
titleText.append(iconString)
附件图像呈现在文本的基线上。并且它的y轴像核心图形坐标系一样反转。如果要向上移动图像，请将 设置bounds.origin.y为正值。
图像应与文本的 capHeight 垂直居中对齐。所以我们需要设置bounds.origin.y为(capHeight - imageHeight)/2.
为了避免对图像产生一些锯齿状的影响，我们应该对 y 的小数部分进行四舍五入。但是字体和图像通常很小，即使是 1px 的差异也会使图像看起来像错位。所以我在划分之前应用了round函数。它使 y 值的小数部分变为 .0 或 .5
在您的情况下，图像高度大于字体的 capHeight。但是你可以用同样的方法。偏移 y 值将为负数。它将从基线的下方进行布局。
试试- [NSTextAttachment bounds]。不需要子类化。
对于上下文，我正在渲染一个UILabel用作附件图像，然后像这样设置边界：
attachment.bounds = CGRectMake(0, self.font.descender, attachment.image.size.width, attachment.image.size.height)标签图像中的文本基线和属性字符串中的文本根据需要排列。
NSTextAttachment您可以通过子类化和覆盖来更改 rect attachmentBoundsForTextContainer:proposedLineFragment:glyphPosition:characterIndex:。例子：
- (CGRect)attachmentBoundsForTextContainer:(NSTextContainer *)textContainer proposedLineFragment:(CGRect)lineFrag glyphPosition:(CGPoint)position characterIndex:(NSUInteger)charIndex {
CGRect bounds;
bounds.origin = CGPointMake(0, -5);
bounds.size = self.image.size;
return bounds;
}
这不是一个完美的解决方案。您必须“通过眼睛”找出 Y 原点，如果您更改字体或图标大小，您可能需要更改 Y 原点。但是我找不到更好的方法，除了将图标放在单独的图像视图中（这有其自身的缺点）。
我找到了一个完美的解决方案，虽然对我来说就像一个魅力，但是你必须自己尝试一下（可能常数取决于设备的分辨率，也许还有什么;）
func textAttachment(fontSize: CGFloat) -> NSTextAttachment {
let font = UIFont.systemFontOfSize(fontSize) //set accordingly to your font, you might pass it in the function
let textAttachment = NSTextAttachment()
let image = //some image
textAttachment.image = image
let mid = font.descender + font.capHeight
textAttachment.bounds = CGRectIntegral(CGRect(x: 0, y: font.descender - image.size.height / 2 + mid + 2, width: image.size.width, height: image.size.height))
return textAttachment
}
应该可以工作并且不应该以任何方式模糊（感谢CGRectIntegral）
What about:
CGFloat offsetY = -10.0;
NSTextAttachment *attachment = [NSTextAttachment new];
attachment.image = image;
attachment.bounds = CGRectMake(0.0,
offsetY,
attachment.image.size.width,
attachment.image.size.height);
No subclassing needed
@Travis 是正确的，偏移量是字体下降器。如果还需要缩放图像，则需要使用 NSTextAttachment 的子类。以下是受本文启发的代码。我也将它作为要点发布。
import UIKit
class ImageAttachment: NSTextAttachment {
var verticalOffset: CGFloat = 0.0
// To vertically center the image, pass in the font descender as the vertical offset.
// We cannot get this info from the text container since it is sometimes nil when `attachmentBoundsForTextContainer`
// is called.
convenience init(_ image: UIImage, verticalOffset: CGFloat = 0.0) {
self.init()
self.image = image
self.verticalOffset = verticalOffset
}
override func attachmentBoundsForTextContainer(textContainer: NSTextContainer, proposedLineFragment lineFrag: CGRect, glyphPosition position: CGPoint, characterIndex charIndex: Int) -> CGRect {
let height = lineFrag.size.height
var scale: CGFloat = 1.0;
let imageSize = image!.size
if (height < imageSize.height) {
scale = height / imageSize.height
}
return CGRect(x: 0, y: verticalOffset, width: imageSize.width * scale, height: imageSize.height * scale)
}
}
使用如下：
var text = NSMutableAttributedString(string: "My Text")
let image = UIImage(named: "my-image")!
let imageAttachment = ImageAttachment(image, verticalOffset: myLabel.font.descender)
text.appendAttributedString(NSAttributedString(attachment: imageAttachment))
myLabel.attributedText = text
如果你有一个非常大的上升点并且想像我一样将图像居中（大写高度的中心）试试这个
let attachment: NSTextAttachment = NSTextAttachment()
attachment.image = image
if let image = attachment.image{
let y = -(font.ascender-font.capHeight/2-image.size.height/2)
attachment.bounds = CGRect(x: 0, y: y, width: image.size.width, height: image.size.height).integral
}
y计算如下图
请注意，y 值为 0，因为我们希望图像从原点向下移动
如果您希望它位于整个标签的中间。使用此 y 值：
let y = -((font.ascender-font.descender)/2-image.size.height/2)
我们可以在 swift 4 中做一个扩展，生成一个带有中心图像的附件，如下所示：
extension NSTextAttachment {
static func getCenteredImageAttachment(with imageName: String, and
font: UIFont?) -> NSTextAttachment? {
let imageAttachment = NSTextAttachment()
guard let image = UIImage(named: imageName),
let font = font else { return nil }
imageAttachment.bounds = CGRect(x: 0, y: (font.capHeight - image.size.height).rounded() / 2, width: image.size.width, height: image.size.height)
imageAttachment.image = image
return imageAttachment
}
}
然后您可以拨打电话发送图像的名称和字体：
let imageAttachment = NSTextAttachment.getCenteredImageAttachment(with: imageName,
and: youLabel?.font)
然后将 imageAttachment 附加到属性字符串
就我而言，调用 sizeToFit() 有帮助。在 Swift 5.1 中
在您的自定义标签内：
func updateUI(text: String?) {
guard let text = text else {
attributedText = nil
return
}
let attributedString = NSMutableAttributedString(string:"")
let textAttachment = NSTextAttachment ()
textAttachment.image = image
let sizeSide: CGFloat = 8
let iconsSize = CGRect(x: CGFloat(0),
y: (font.capHeight - sizeSide) / 2,
width: sizeSide,
height: sizeSide)
textAttachment.bounds = iconsSize
attributedString.append(NSAttributedString(attachment: textAttachment))
attributedString.append(NSMutableAttributedString(string: text))
attributedText = attributedString
sizeToFit()
}
Please use -lineFrag.size.height/5.0 for the bounds height. This exactly centres the image and aligned with text for all the size of fonts
override func attachmentBoundsForTextContainer(textContainer: NSTextContainer, proposedLineFragment lineFrag: CGRect, glyphPosition position: CGPoint, characterIndex charIndex: Int) -> CGRect
{
var bounds:CGRect = CGRectZero
bounds.size = self.image?.size as CGSize!
bounds.origin = CGPointMake(0, -lineFrag.size.height/5.0);
return bounds;
}