iphone/ipad：究竟如何使用 NSAttributedString？

@interface ExampleHTMLStringToAttributedString : NSObject<NSXMLParserDelegate>

+(NSAttributedString*) getAttributedStringForHTMLText:(NSString*)htmlText WithFontSize:(CGFloat)fontSize;

@end

@interface ExampleHTMLStringToAttributedString()
@property NSString *mpString;
@property NSMutableAttributedString *mpAttributedString;

@property CGFloat mfFontSize;
@property NSMutableString *appendThisString;
@property BOOL mbIsBold;
@property BOOL mbIsItalic;
@end

@implementation ExampleHTMLStringToAttributedString
@synthesize mpString;
@synthesize mfFontSize;
@synthesize mpAttributedString;
@synthesize appendThisString;
@synthesize mbIsBold;
@synthesize mbIsItalic;

+(NSAttributedString*) getAttributedStringForHTMLText:(NSString*)htmlText WithFontSize:(CGFloat)fontSize {

    ExampleHTMLStringToAttributedString *me = [[ExampleHTMLStringToAttributedString alloc] initWithString:htmlText];
    return [me getAttributedStringWithFontSize:fontSize];
}

- (id)initWithString:(NSString*)inString {
    self = [super init];
    if (self) {
        if ([inString hasPrefix:@""]) {
          mpString = inString;
        } else {
            mpString = [NSString stringWithFormat:@"%@", inString];
        }
        mpAttributedString = [NSMutableAttributedString new];
    }
    return self;
}

-(NSAttributedString*) getAttributedStringWithFontSize:(CGFloat)fontSize {

    mfFontSize = fontSize;

    // Parse the XML
    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:[mpString dataUsingEncoding:NSUTF8StringEncoding]];
    parser.delegate = self;
    if (![parser parse]) {
        return nil;
    }

    return mpAttributedString;
}

-(void) appendTheAccumulatedText {
    UIFont *theFont = nil;

    if (mbIsBold && mbIsItalic) {
        // http://stackoverflow.com/questions/1384181/italic-bold-and-underlined-font-on-iphone
        theFont = [UIFont fontWithName:@"Helvetica-BoldOblique" size:mfFontSize];
    } else if (mbIsBold) {
       theFont = [UIFont boldSystemFontOfSize:mfFontSize];
    } else if (mbIsItalic) {
        theFont = [UIFont italicSystemFontOfSize:mfFontSize];
    } else {
        theFont = [UIFont systemFontOfSize:mfFontSize];
    }

    NSAttributedString *appendThisAttributedString =
    [[NSAttributedString alloc]
     initWithString:appendThisString
     attributes:@{NSFontAttributeName : theFont}];

    [mpAttributedString appendAttributedString:appendThisAttributedString];

    [appendThisString setString:@""];
}

#pragma NSXMLParserDelegate delegate

-(void)parserDidStartDocument:(NSXMLParser *)parser{
    appendThisString = [NSMutableString new];
    mbIsBold = NO;
    mbIsItalic = NO;
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict {
    if ([elementName isEqualToString:@"body"]){
    } else if ([elementName isEqualToString:@"i"]) {
      [self appendTheAccumulatedText];
        mbIsItalic = YES;
    } else if ([elementName isEqualToString:@"b"]) {
      [self appendTheAccumulatedText];
        mbIsBold = YES;
    }
}

-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
    if ([elementName isEqualToString:@"body"]){
      [self appendTheAccumulatedText];
    } else if ([elementName isEqualToString:@"i"]) {
      [self appendTheAccumulatedText];
      mbIsItalic = NO;
    } else if ([elementName isEqualToString:@"b"]) {
        [self appendTheAccumulatedText];
        mbIsBold = NO;
    }
}

-(void)parserDidEndDocument:(NSXMLParser *)parser{
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
    [appendThisString appendString:string];
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError {
}

@end

要使用，请执行以下操作：

  self.myTextView.attributedText = [ExampleHTMLStringToAttributedString getAttributedStringForHTMLText:@"this is <b>bold</b> text" WithFontSize:self.myTextView.pointSize];