iOS NSXML 解析器 - 从 XML 标签一致地导出图像源 URL

Question

我在我的应用程序中使用 RSS 提要，特别是 Drudge Report 的。我对这类东西很陌生，对使用 Xcode 的 NSXMLParser 也是陌生的。每个提要显然代表一篇文章。每个提要都由 <item></item> 标签表示。

在这些标签中，<description></description> 标签包含对信息的描述。在描述中，某些文章可能有与该文章关联的图像，如以下屏幕截图所示：

我突出显示的部分是我需要获取的图像（具体来说，URL 字符串）。我能够将每篇文章的描述导出为 NSMutableString，但是当我使用 NSXMLParser 解析 XML 时，如何导出图像的 URL？以下是我如何完成所有这些的代码：

@interface ViewController () <NSXMLParserDelegate, UITableViewDataSource, UITableViewDelegate> {
    NSXMLParser *parser;
    NSMutableArray *feeds;
    NSMutableDictionary *item;
    NSMutableString *title;
    NSMutableString *link;
    NSMutableString *description;
    NSString *element;
}
.
.(other code)
.
#pragma mark - NSXMLParserDelegate

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    element = elementName;
    if ([element isEqualToString:@"item"]) {
        item        = [[NSMutableDictionary alloc] init];
        title       = [[NSMutableString alloc] init];
        link        = [[NSMutableString alloc] init];
        description = [[NSMutableString alloc] init];
    }
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {

    if ([element isEqualToString:@"title"]) {
        [title appendString:string];
    }
    else if ([element isEqualToString:@"feedburner:origLink"]) {
        [link appendString:string];
    }
    else if ([element isEqualToString:@"description"]) {
        [description appendString:string];
    }
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    if ([elementName isEqualToString:@"item"]) {
        NSString *filteredTitle = [title stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSString *filteredLink = [link stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if (![filteredLink containsString:@"https://itunes.apple.com/"]) {
            [item setObject:filteredTitle forKey:@"title"];
            [item setObject:filteredLink forKey:@"link"];
            [item setObject:description forKey:@"description"];

            [feeds addObject:[item copy]];
        }
    }
}

- (void)parserDidEndDocument:(NSXMLParser *)parser {
    [self.tableView reloadData];
}

进度

到目前为止，我在 didEndElement 方法中添加了以下内容：

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {

    if ([elementName isEqualToString:@"item"]) {
        NSString *filteredTitle = [title stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSString *filteredLink = [link stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if (![filteredLink containsString:@"https://itunes.apple.com/"]) {
            [item setObject:filteredTitle forKey:@"title"];
            [item setObject:filteredLink forKey:@"link"];
            [item setObject:description forKey:@"description"];
            if ([description rangeOfString:@"img style"].location != NSNotFound)
            {

            }

            [feeds addObject:[item copy]];
        }
    }
}

现在我知道描述中有 img style 字符串，我需要获取 src="whateverImageURL"。如何使用正则表达式获取此图像的第一次出现 URL?

Answer 1

你必须执行这个协议

- (void)parser:(NSXMLParser *)parser foundAttributeDeclarationWithName:(NSString *)attributeName forElement:(NSString *)elementName type:(nullable NSString *)type defaultValue:(nullable NSString *)defaultValue;

这允许您获取找到的每个元素的所有属性。

如果这对你有帮助，请告诉我:)

更新

这里是一个代码，用于查找在给定字符串中找到的第一个 img 的 url

 NSString *descriptionString = @"&lt;br&gt;&lt;tt&gt;&lt;font size=\"3\" color=\"blue\"&gt;&lt;b&gt;&lt;u&gt;LIST: 10 Worst Winter Storms in Washington History...&lt;/u&gt;&lt;/b&gt;&lt;/font&gt;&lt;/tt&gt;&lt;br&gt;&lt;br&gt;&lt;br&gt;&lt;font face=\"Arial\" size=\"1\"&gt;&lt;i&gt;(Top headline, 3rd story, &lt;a href=\"http://www.nbcwashington.com/news/local/Ten-Worst-Storms-in-DC-History-365815301.html\"&gt;link&lt;/a&gt;)&lt;/i&gt;&lt;/font&gt;&lt;hr style=\"height: 1px; border-style: none; color: #666666; background-color: #666666;\"/&gt;&lt;font face=\"Arial\" size=\"2\"&gt;Related stories:&lt;div class=\"related-links\" id=\"R:H1:S3\"&gt;&lt;a href=\"http://www.wunderground.com/US/DC/001.html#WIN\"&gt;BLIZZARD WARNING ISSUED FOR DC; BURBS UP TO 30\"...&lt;/a&gt;&lt;br&gt;&lt;a href=\"http://washington.cbslocal.com/2016/01/19/winter-is-finally-here-deep-freeze-and-snow-in-the-forecast/\"&gt;Mayor Requests Help From National Guard...&lt;/a&gt;&lt;br&gt;&lt;a href=\"http://www.accuweather.com/en/weather-news/snow-storm-travel-disruptions-aim-for-nyc-dc-boston-philadelphia-friday-saturday/54870622\"&gt;UPDATE...&lt;/a&gt;&lt;br&gt;&lt;a href=\"http://www.infowars.com/snowmaggedon2016-empty-store-shelves-as-panicked-shoppers-ransack-grocery-stores/\"&gt;Anxious Shoppers Ransack Grocery Stores...&lt;/a&gt;&lt;br&gt;&lt;a href=\"http://motherboard.vice.com/read/dark-web-users-are-worried-snowstorm-jonas-will-disrupt-their-deliveries\"&gt;Dark Web Users Fear Delivery Disruptions...&lt;/a&gt;&lt;br&gt;&lt;a href=\"https://www.washingtonpost.com/news/to-your-health/wp/2016/01/21/heres-why-some-people-drop-dead-while-shoveling-snow/\"&gt;Cold weather, shoveling form heart attack 'perfect storm'...&lt;/a&gt;&lt;br&gt;&lt;/div&gt;&lt;/font&gt;&lt;br&gt;&lt;div class=\"feedflare\"&gt;    &lt;a href=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?a=Mtf4NlmV8XU:vDGXzaysxPw:yIl2AUoC8zA\"&gt;&lt;img src=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?d=yIl2AUoC8zA\" border=\"0\"&gt;&lt;/img&gt;&lt;/a&gt; &lt;a href=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?a=Mtf4NlmV8XU:vDGXzaysxPw:V_sGLiPBpWU\"&gt;&lt;img src=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?i=Mtf4NlmV8XU:vDGXzaysxPw:V_sGLiPBpWU\" border=\"0\"&gt;&lt;/img&gt;&lt;/a&gt; &lt;a href=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?a=Mtf4NlmV8XU:vDGXzaysxPw:qj6IDK7rITs\"&gt;&lt;img src=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?d=qj6IDK7rITs\" border=\"0\"&gt;&lt;/img&gt;&lt;/a&gt; &lt;a href=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?a=Mtf4NlmV8XU:vDGXzaysxPw:gIN9vFwOqvQ\"&gt;&lt;img src=\"http://feeds.feedburner.com/~ff/DrudgeReportFeed?i=Mtf4NlmV8XU:vDGXzaysxPw:gIN9vFwOqvQ\" border=\"0\"&gt;&lt;/img&gt;&lt;/a&gt; &lt;/div&gt;&lt;img src=\"http://feeds.feedburner.com/~r/DrudgeReportFeed/~4/Mtf4NlmV8XU\" height=\"1\" width=\"1\" alt=\"\"/&gt";
NSString *stringWithoutWhiteSpace = [descriptionString stringByReplacingOccurrencesOfString:@" " withString:@""];
NSInteger srcLocation = [stringWithoutWhiteSpace rangeOfString:@"src="].location;
if ( srcLocation!= NSNotFound) {
    NSString *firstSrcImg = [stringWithoutWhiteSpace substringFromIndex:srcLocation];
    NSArray *componment = [firstSrcImg componentsSeparatedByString:@"\""];
    NSString *url = componment[1];
    NSLog(@"%@", url);
}

我邀请您试用并告诉我它是否能回答您的问题... 我可以给出另一个代码 return all img urls :)

第二次更新 例如，我在这里做了一个你可以使用的方法：

- (NSString*) getNextURLFromString:(NSString*) str withURLTag:(NSString*) urlTag{
NSString *stringWithoutWhiteSpace = [str stringByReplacingOccurrencesOfString:@" " withString:@""];
NSInteger srcLocation = [stringWithoutWhiteSpace rangeOfString:urlTag].location;
if ( srcLocation!= NSNotFound) {
    NSString *firstSrcImg = [stringWithoutWhiteSpace substringFromIndex:srcLocation];
    NSArray *componment = [firstSrcImg componentsSeparatedByString:@"\""];
    NSString *url = componment[1];
    return url;
}
return nil;
}

对于 urlTag 参数放 @"src=" 并为 str 参数添加描述标签值

更新 3

这里有一个方法 return 所有图像 url

- (NSArray*) getAllURLFromString:(NSString*) str withURLTag:(NSString*) urlTag{
NSMutableArray *result = [NSMutableArray array];
NSString *stringWithoutWhiteSpace = [str stringByReplacingOccurrencesOfString:@" " withString:@""];
NSInteger srcLocation = [stringWithoutWhiteSpace rangeOfString:urlTag].location;
if ( srcLocation!= NSNotFound) {
    NSString *firstSrcImg = [stringWithoutWhiteSpace substringFromIndex:srcLocation];
    NSArray *componment = [firstSrcImg componentsSeparatedByString:@"\""];
    if ([componment count]>1) {
        NSString *url = componment[1];
        [result addObject:url];

        NSArray *nextComponent = [stringWithoutWhiteSpace componentsSeparatedByString:url];
        if ([nextComponent count]>1) {
            [result addObjectsFromArray:[self getAllURLFromString:nextComponent[1] withURLTag:urlTag]];
        }
    }

    return result;
}
return result;
}

对于 urlTag 参数放 @"src="

并为 str 参数添加描述标签值

Answer 2

您必须在

中执行以下操作

foundCharacters: method.

   else if ([element isEqualToString:@"description"]) 
{
        [description appendString:string];
if ([description rangeOfString:@"img"].location != NSNotFound)
    {
        NSRange firstRange = [previewImage rangeOfString:@"src="];
        NSRange endRange = [[previewImage substringFromIndex:firstRange.location] rangeOfString:@" width=\""];
        NSString *finalLink = [[NSString alloc] init];
        finalLink = [previewImage substringWithRange:NSMakeRange(firstRange.location, endRange.location)];
        NSString *match = @"src=\"";
        NSString *postMatch;
        NSScanner *scanner = [NSScanner scannerWithString:finalLink];
        [scanner scanString:match intoString:nil];
        postMatch = [finalLink substringFromIndex:scanner.scanLocation];
        NSString *finalURL = [postMatch stringByAppendingString:@""];
        description = finalURL;
    }
    }
}

因为在你的 foundCharacters 中，你已经获得了描述标签你需要在你的描述数组中搜索你追加的文本字符串。
你可以扫描整个字符串然后存储所需的变量中的子字符串...即 ur URL link
使用 firstRange 变量设置 ull 获取字符串的范围
和 endrange 变量将文本设置到您希望字符串结束的位置（在您的情况下 url）

这里我将 URL 存储在 previewImage 中。

希望它对你有用......

Answer 3

经过一些研究，我设法解决了我的问题。我只是需要一些使用 NSRange 的练习。在我的例子中，这个想法是，当我有一个包含 NSString "img style" 的描述时，我知道我需要第一个 "src="whateverImageURL" 字符串可以得到。我在下面的代码中这样做：

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    if ([elementName isEqualToString:@"item"]) {
        NSString *filteredTitle = [title stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSString *filteredLink = [link stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if (![filteredLink containsString:@"https://itunes.apple.com/"]) {
            [item setObject:filteredTitle forKey:@"title"];
            [item setObject:filteredLink forKey:@"link"];
            [item setObject:description forKey:@"description"];
            if ([description rangeOfString:@"img style"].location != NSNotFound) {
                NSString *finalImageURL;
                NSRange startRange = [description rangeOfString:@"src=\""];
                finalImageURL = [description substringFromIndex:startRange.location];
                finalImageURL = [finalImageURL substringFromIndex:startRange.length];
                NSRange endRange = [finalImageURL rangeOfString:@"\""];
                finalImageURL = [finalImageURL substringToIndex:endRange.location];
            }

            [feeds addObject:[item copy]];
        }
    }
}

iOS NSXML 解析器 - 从 XML 标签一致地导出图像源 URL

iOS NSXMLParser - Consistently Derive Image Source URL From XML Tag

xml

rss

objective-c

nsxmlparser

ios