在不修改其他属性的情况下替换 NSAttributedString 中的整个文本字符串

Question

我有对 NSAttributedString 的引用，我想更改属性字符串的文本。

我想我必须创建一个新的 NSAttributedString 并用这个新字符串更新引用。但是，当我这样做时，我丢失了先前字符串的属性。

NSAttributedString *newString = [[NSAttributedString alloc] initWithString:text];
[self setAttributedText:newString];

我参考了 self.attributedText 中的旧属性字符串。如何在新字符串中保留之前的属性？

Answer 1

您可以使用 NSMutableAttributedString 并只更新字符串，属性不会改变。示例：

NSMutableAttributedString *mutableAttributedString = [[NSMutableAttributedString alloc] initWithString:@"my string" attributes:@{NSForegroundColorAttributeName: [UIColor blueColor], NSFontAttributeName: [UIFont systemFontOfSize:20]}];

//update the string
[mutableAttributedString.mutableString setString:@"my new string"];

Answer 2

Swift

在保留属性的同时更改文本：

let myString = "my string"
let myAttributes = [NSAttributedString.Key.foregroundColor: UIColor.blue, NSAttributedString.Key.font: UIFont.systemFont(ofSize: 40)]
let mutableAttributedString = NSMutableAttributedString(string: myString, attributes: myAttributes)

let myNewString = "my new string"
mutableAttributedString.mutableString.setString(myNewString)

mutableAttributedString 的结果是

备注

超过索引 0 的任何 sub-ranges 属性都将被丢弃。例如，如果我在原始字符串的最后一个单词上添加另一个属性，则在我更改字符串后它会丢失：

// additional attribute added before changing the text
let myRange = NSRange(location: 3, length: 6)
let anotherAttribute = [ NSAttributedString.Key.backgroundColor: UIColor.yellow ]
mutableAttributedString.addAttributes(anotherAttribute, range: myRange)

结果：

由此我们可以看出，新字符串获取了原始字符串索引 0 处的所有属性。实际上，如果我们将范围调整为

let myRange = NSRange(location: 0, length: 1)

我们得到

另见

my main answer about Swift attributed strings

Answer 3

这是使用Objective-C的方式（在iOS 9上测试过）

NSAttributedString *primaryString = ...;
NSString *newString = ...;

//copy the attributes
NSDictionary *attributes = [primaryString attributesAtIndex:0 effectiveRange:NSMakeRange(primaryString.length-1, primaryString.length)];
NSMutableAttributedString *newString = [[NSMutableAttributedString alloc] initWithString:newString attributes:attributes];
NSMutableAttributedString *primaryStringMutable = [[NSMutableAttributedString alloc] initWithAttributedString:primaryString];

//change the string
[primaryStringMutable setAttributedString::newString];

primaryString = [NSAttributedString alloc] initWithAttributedString:primaryStringMutable];

检查最重要的参考文献：attributesAtIndex:effectiveRange: and setAttributedString:。

Answer 4

Darius 的答案就快出来了。它包含一个小错误。正确的是：

这是使用Objective-C的方式（在iOS 10上测试过）

NSAttributedString *primaryString = ...;
NSString *newString = ...;

//copy the attributes
NSRange range = NSMakeRange(primaryString.length-1, primaryString.length);
NSDictionary *attributes = [primaryString attributesAtIndex:0 effectiveRange:&range];
NSMutableAttributedString *newString = [[NSMutableAttributedString alloc] initWithString:newString attributes:attributes];
NSMutableAttributedString *primaryStringMutable = [[NSMutableAttributedString alloc] initWithAttributedString:primaryString];

//change the string
[primaryStringMutable setAttributedString::newString];

primaryString = [NSAttributedString alloc] initWithAttributedString:primaryStringMutable];

Answer 5

我做了一些扩展，使这变得非常简单：

import UIKit

extension UILabel {
    func setTextWhileKeepingAttributes(string: String) {
        if let newAttributedText = self.attributedText {
            let mutableAttributedText = newAttributedText.mutableCopy()

            mutableAttributedText.mutableString.setString(string)

            self.attributedText = mutableAttributedText as? NSAttributedString
        }
    }
}

https://gist.github.com/wvdk/e8992e82b04e626a862dbb991e4cbe9c

Answer 6

对于那些使用 UIButtons 的人，这是一个基于的改进答案。

看来更新按钮的标签最好这样：

let newtext = "my new text"
myuibutton.setAttributedTitle(titlelabel.getTextWhileKeepingAttributes(string: newtext), for: .normal)

所以我得到了这个扩展：

import UIKit

extension UILabel {
    func setTextWhileKeepingAttributes(string: String) {
        if let newAttributedText = self.attributedText {
            let mutableAttributedText = newAttributedText.mutableCopy()

            (mutableAttributedText as AnyObject).mutableString.setString(string)

            self.attributedText = mutableAttributedText as? NSAttributedString
        }
    }
    func getTextWhileKeepingAttributes(string: String) -> NSAttributedString {
        if let newAttributedText:NSAttributedString = self.attributedText {
            let mutableAttributedText = newAttributedText.mutableCopy()

            (mutableAttributedText as AnyObject).mutableString.setString(string)
            return mutableAttributedText as! NSAttributedString
        }
        else {
            // No attributes in this label, just create a new attributed string?
            let attributedstring = NSAttributedString.init(string: string)
            return attributedstring
        }
    }
}

Answer 7

更改可变字符串的文本将不起作用，因为它只会保留第一个字符的属性并将其应用于所有文本。这似乎是设计使然，因为它是文档的一部分。

所以如果你想复制所有的属性或者改变字符串，你需要手动复制所有的属性。然后您可以创建一个 MutableAttributedString 并更改文本。然后将所有属性应用到新的 MutableAttributedString。

我已经为 Xamarin（在 C# 中）这样做了，但我认为你可以很容易地理解它并适应你的语言：

NSMutableAttributedString result = new 
NSMutableAttributedString(attrStr.Value.Replace(blackSquare, bullet));
// You cannot simply replace an AttributedString's string, because that will discard attributes. 
// Therefore, I will now copy all attributes manually to the new MutableAttributedString:
NSRange outRange = new NSRange(0, 0);
int attributeIndex = 0;
while (outRange.Location + outRange.Length < attrStr.Value.Length   // last attribute range reached
            && attributeIndex < attrStr.Value.Length)                    // or last character reached
{
       // Get all attributes for character at attributeIndex
       var attributes = attrStr.GetAttributes(attributeIndex, out outRange);
       if (attributes != null && attributes.Count > 0)
       {
               result.AddAttributes(attributes, outRange); // copy all found attributes to result
               attributeIndex = (int)(outRange.Location + outRange.Length); // continue with the next range
       }
       else
       {
               attributeIndex++; // no attribues at the current attributeIndex, so continue with the next char
       }

}
// all attributes are copied

Answer 8

        let mutableAttributedString  = mySubTitleLabel.attributedText?.mutableCopy() as? NSMutableAttributedString
        if let attrStr = mutableAttributedString{
            attrStr.mutableString.setString("Inner space can be an example shown on the, third page of the tutorial.")
            mySubTitleLabel.attributedText = attrStr;
        }

希望这段代码对你有帮助，我已经将标签的属性复制到一个 mutableAttributedString 中，然后为其设置字符串

Answer 9

None 个答案对我有用，但是这个；

extension UILabel{
func setTextWhileKeepingAttributes(_ string: String) {
        if let attributedText = self.attributedText {
            let attributedString = NSMutableAttributedString(string: string,
                                                             attributes: [NSAttributedString.Key.font: font])
            attributedText.enumerateAttribute(.font, in: NSRange(location: 0, length: attributedText.length)) { (value, range, stop) in
                let attributes = attributedText.attributes(at: range.location, effectiveRange: nil)
                attributedString.addAttributes(attributes, range: range)
            }
            self.attributedText = attributedString
        }
    }
}

在不修改其他属性的情况下替换 NSAttributedString 中的整个文本字符串

replace entire text string in NSAttributedString without modifying other attributes

ios

objective-c

nsattributedstring

Swift