问题
i have a problem with NSAttributedString ...
I want to convert a HTML string into an NSAttributedString and then work on the NSAttributedString (change some colors, fontsize, fontfamily, background- , foreground-Color) and then convert back plain HTML text from the NSAttributedString.
Converting isn't a problem, but on each time I convert HTML to NSAS and back the fontsize getting bigger and bigger ?!
Here is a picture and source code of my playground.
// Playground - noun: a place where people can play
// NSAS: - NSAttributedString
import UIKit
class Wrapper {
//MARK: fields
let apiHtml = "<div style='font-size: 18px'><span style='font-family:'andale mono', times;'>Dies</span> <span style='font-family:'comic sans ms', sans-serif;'>ist</span> <strong><span style='font-family:'andale mono', sans-serif;';>eine</span></strong> <em>formatierte</em> <span style='text-decoration:underline;'>Karte</span> <span style='font-size:16px;'>die</span> <span style='background-color:#ffff00;'>es</span> zu Übernehmen gilt</div>"
var newGeneratedHtml = ""
var textView : UITextView!
//MARK: constructor
init() {
//init textview
textView = UITextView(frame: CGRectMake(0, 0, 500, 300))
//convert html into NSAS and set it to textview
if let attributedText = getAttributedTextFromApiHtmlString(apiHtml) {
textView.attributedText = attributedText
}
//get html text from textfields NSAS
if let htmlText = getHtmlTextFromTextView() {
newGeneratedHtml = htmlText
println(htmlText)
}
//set the converted html from textfields NSAS
if let attributedText = getAttributedTextFromApiHtmlString(newGeneratedHtml) {
textView.attributedText = attributedText
}
//get html text from textfields NSAS
if let htmlText = getHtmlTextFromTextView() {
newGeneratedHtml = htmlText
println(htmlText)
}
}
//MARK: methods
func getAttributedTextFromApiHtmlString(text : String) -> NSAttributedString? {
if let attributedText = NSAttributedString(data: text.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: true)!, options: [NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType], documentAttributes: nil, error: nil) {
return attributedText
}
return nil
}
func getHtmlTextFromTextView() -> String? {
let attributedTextFromTextView = textView.attributedText
if let htmlData = attributedTextFromTextView.dataFromRange(NSMakeRange(0, attributedTextFromTextView.length), documentAttributes: [NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType], error: nil) {
if let htmlString = NSString(data: htmlData, encoding: NSUTF8StringEncoding) {
return htmlString
}
}
return nil
}
}
var w = Wrapper()
Here is the playground result, you can see that the second text is bigger then the first text but I didn't change the font size anywhere.
Is this a bug or had I have to set a fix font size?
But setting a fixed font size is not what I really want because it can be different for each char ...
UPDATE:
I accept @Lou Franco answer because he is right. I don´t know why he is convert px to pt and back but here is my workaround:
func getAttributedTextFromApiHtmlString(text : String) -> NSAttributedString? {
if let attributedText = NSAttributedString(data: text.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!, options: [NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType], documentAttributes: nil, error: nil) {
var res : NSMutableAttributedString = attributedText.mutableCopy() as NSMutableAttributedString
res.beginEditing()
var found : Bool = false;
res.enumerateAttribute(NSFontAttributeName, inRange:NSMakeRange(0, res.length) ,options:NSAttributedStringEnumerationOptions.allZeros, usingBlock: {(value:AnyObject!, range:NSRange, stop:UnsafeMutablePointer<ObjCBool>) -> Void in
if ((value) != nil) {
let oldFont = value as UIFont;
let newFont = oldFont.fontWithSize(15)
res.removeAttribute(NSFontAttributeName, range:range)
res.addAttribute(NSFontAttributeName, value: newFont, range: range)
found = true
}
})
if !found {
// No font was found - do something else?
}
res.endEditing()
return res
}
return nil
}
The only disadvantage of this is that you lose different Text-Heights in your AttributedString....
Now i have to find a way to keep the different Text-Heights ... If anybody has the solution or better work around feel free to post your answer.
回答1:
It's probably rounding errors in the round-trip. Try using integer point sizes (with pt instead of px)
Ok, looking at your console output, it's translating your px to pt, so maybe you can hack it by taking the HTML that comes from the conversion and changing pt back to px.
回答2:
I solved this by applying 0.75 ratio on each fond size in your string. Say if you have multiple fonts in your attributed string, when you looping though all of them, simple apply the ratio and then you are all set. Here is my code in swift 3.0:
yourAttrStr.beginEditing()
yourAttrStr.enumerateAttribute(NSFontAttributeName, in: NSMakeRange(0, yourAttrStr.length), options: .init(rawValue: 0)) {
(value, range, stop) in
if let font = value as? UIFont {
let resizedFont = font.withSize(font.pointSize * 0.75)
yourAttrStr.addAttribute(NSFontAttributeName, value: resizedFont, range: range)
}
}
yourAttrStr.endEditing()//yourAttrStr will be the same size as html string
This is the piece of code that is running in my application
extension String {
func htmlAttributedString() -> NSAttributedString? {
guard let data = self.data(using: String.Encoding.utf16, allowLossyConversion: false) else { return nil }
guard let html = try? NSMutableAttributedString(
data: data,
options: [NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType],
documentAttributes: nil) else { return nil }
html.beginEditing()
html.enumerateAttribute(NSFontAttributeName, in: NSMakeRange(0, html.length), options: .init(rawValue: 0)) {
(value, range, stop) in
if let font = value as? UIFont {
let resizedFont = font.withSize(font.pointSize * 0.75)
html.addAttribute(NSFontAttributeName,
value: resizedFont,
range: range)
}
}
html.endEditing()
return html
}
}
To use it:
let htmlStr: String = "<font size=\"6\">font a</font><font size=\"16\">Font b</font>"
let attriStr: NSAttributedString? = htmlStr.htmlAttributedString()
回答3:
In Swift 3 taking @fangming's solution, that worked for me:
func newAttrSize(blockQuote: NSAttributedString) -> NSAttributedString
{
let yourAttrStr = NSMutableAttributedString(attributedString: blockQuote)
yourAttrStr.enumerateAttribute(.font, in: NSMakeRange(0, yourAttrStr.length), options: .init(rawValue: 0)) {
(value, range, stop) in
if let font = value as? UIFont {
let resizedFont = font.withSize(font.pointSize * 0.75)
yourAttrStr.addAttribute(.font, value: resizedFont, range: range)
}
}
return yourAttrStr
}
来源：https://stackoverflow.com/questions/28441486/html-to-nsattributedstring-and-nsattributedstring-to-html