iOS开发:与网页加载相关的字符串操作技巧

• 需求1

有的html字符串中无法显示\，而是显示为"。这时需要将"等类似的字符转化为HTML中的\等。还有<和>等本应该代表标签符号的字符，也需要换成<和>等。

- (NSString *)htmlEntityDecode:(NSString *)string
{
    string = [string stringByReplacingOccurrencesOfString:@""" withString:@"\""];
    string = [string stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    string = [string stringByReplacingOccurrencesOfString:@"&lt;" withString:@"<"];
    string = [string stringByReplacingOccurrencesOfString:@"&gt;" withString:@">"];
    string = [string stringByReplacingOccurrencesOfString:@"&amp;" withString:@"&"]; // Do this last so that, e.g. @"&amp;lt;" goes to @"&lt;" not @"<"
    
    return string;
}

• 需求2

将HTML字符串转化为NSAttributedString富文本字符串，并用UILabel，UITextview的attributedText属性加载富文本。

- (NSAttributedString *)attributedStringWithHTMLString:(NSString *)htmlString
{
    NSDictionary *options = @{ NSDocumentTypeDocumentAttribute : NSHTMLTextDocumentType,
                               NSCharacterEncodingDocumentAttribute :@(NSUTF8StringEncoding) };
    
    NSData *data = [htmlString dataUsingEncoding:NSUTF8StringEncoding];
    
    return [[NSAttributedString alloc] initWithData:data options:options documentAttributes:nil error:nil];
}

• 需求3

忽略所有格式，取出纯文本内容，即去掉 HTML 字符串中的所有标签。

- (NSString *)filterHTML:(NSString *)html
{
    NSScanner * scanner = [NSScanner scannerWithString:html];
    NSString * text = nil;
    while([scanner isAtEnd]==NO)
    {
        //找到标签的起始位置
        [scanner scanUpToString:@"<" intoString:nil];
        //找到标签的结束位置
        [scanner scanUpToString:@">" intoString:&text];
        //替换字符
        html = [html stringByReplacingOccurrencesOfString:[NSString stringWithFormat:@"%@>",text] withString:@""];
    }
    //    NSString * regEx = @"<([^>]*)>";
    //    html = [html stringByReplacingOccurrencesOfString:regEx withString:@""];
    return html;
}