开源 html 解析类不能正确解析段落之间的空格答案

【问题标题】：Open source html parsing class not properly parsing spaces between paragraphs开源 html 解析类不能正确解析段落之间的空格
【发布时间】：2012-10-28 07:16:25
【问题描述】：

我正在使用一种将 html 文本解析为 NSString 的开源方法。

生成的字符串在前几段之间有大量空白，但后续段落只有一行空格。这是一个输出示例。

以下是我正在调用的方法。我只更改了两行代码。对于stopCharacters 和newLineAndWhitespaceCharacters，我从字符集中删除了/n，因为当包含它时，整个文本就是一个长段落。

- (NSString *)stringByConvertingHTMLToPlainText {

    // Pool
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    // Character sets
    NSCharacterSet *stopCharacters = [NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat:@"< \t\r%C%C%C%C", 0x0085, 0x000C, 0x2028, 0x2029]];
    NSCharacterSet *newLineAndWhitespaceCharacters = [NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat:@" \t\r%C%C%C%C", 0x0085, 0x000C, 0x2028, 0x2029]];
    NSCharacterSet *tagNameCharacters = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"];

    // Scan and find all tags
    NSMutableString *result = [[NSMutableString alloc] initWithCapacity:self.length];
    NSScanner *scanner = [[NSScanner alloc] initWithString:self];
    [scanner setCharactersToBeSkipped:nil];
    [scanner setCaseSensitive:YES];
    NSString *str = nil, *tagName = nil;
    BOOL dontReplaceTagWithSpace = NO;
    do {

        // Scan up to the start of a tag or whitespace
        if ([scanner scanUpToCharactersFromSet:stopCharacters intoString:&str]) {
            [result appendString:str];
            str = nil; // reset
        }

        // Check if we've stopped at a tag/comment or whitespace
        if ([scanner scanString:@"<" intoString:NULL]) {

            // Stopped at a comment or tag
            if ([scanner scanString:@"!--" intoString:NULL]) {

                // Comment
                [scanner scanUpToString:@"-->" intoString:NULL];
                [scanner scanString:@"-->" intoString:NULL];

            } else {

                // Tag - remove and replace with space unless it's
                // a closing inline tag then dont replace with a space
                if ([scanner scanString:@"/" intoString:NULL]) {

                    // Closing tag - replace with space unless it's inline
                    tagName = nil; dontReplaceTagWithSpace = NO;
                    if ([scanner scanCharactersFromSet:tagNameCharacters intoString:&tagName]) {
                        tagName = [tagName lowercaseString];
                        dontReplaceTagWithSpace = ([tagName isEqualToString:@"a"] ||
                                                   [tagName isEqualToString:@"b"] ||
                                                   [tagName isEqualToString:@"i"] ||
                                                   [tagName isEqualToString:@"q"] ||
                                                   [tagName isEqualToString:@"span"] ||
                                                   [tagName isEqualToString:@"em"] ||
                                                   [tagName isEqualToString:@"strong"] ||
                                                   [tagName isEqualToString:@"cite"] ||
                                                   [tagName isEqualToString:@"abbr"] ||
                                                   [tagName isEqualToString:@"acronym"] ||
                                                   [tagName isEqualToString:@"label"]);
                    }

                    // Replace tag with string unless it was an inline
                    if (!dontReplaceTagWithSpace && result.length > 0 && ![scanner isAtEnd]) [result appendString:@" "];

                }

                // Scan past tag
                [scanner scanUpToString:@">" intoString:NULL];
                [scanner scanString:@">" intoString:NULL];

            }

        } else {

            // Stopped at whitespace - replace all whitespace and newlines with a space
            if ([scanner scanCharactersFromSet:newLineAndWhitespaceCharacters intoString:NULL]) {
                if (result.length > 0 && ![scanner isAtEnd]) [result appendString:@" "]; // Dont append space to beginning or end of result
            }

        }

    } while (![scanner isAtEnd]);

    // Cleanup
    [scanner release];

    // Decode HTML entities and return
    NSString *retString = [[result stringByDecodingHTMLEntities] retain];
    [result release];

    // Drain
    [pool drain];

    // Return
    return [retString autorelease];

}

编辑：

这里是字符串的 NSLog。我只粘贴了前几段

Mitt Romney spent the past six years running for president. After his loss to President Barack Obama, he'll have to chart a different course.  


 His initial plan: spend time with his family. He has five sons and 18 grandchildren, with a 19th on the way.  






 "I don't look at postelection to be a time of regrouping. Instead it's a time of forward focus," Romney told reporters aboard his plane Tuesday evening as he returned to Boston after the final campaign stop of his political career. "I have, of course, a family and life important to me, win or lose."  

 The most visible member of that family — wife Ann Romney — says neither she nor her husband will seek political office again.

等等……

for (int j = 25; j< 50; j++) {
    char test =  [completeTrimmed characterAtIndex:([completeTrimmed rangeOfString:@"chart a different course."].location + j)];

        NSLog(@"%hhd", test);
    }

012-11-11 17:15:57.668 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.669 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.669 LMU_LAL_LAUNCHER[5431:c07] 10
2012-11-11 17:15:57.670 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.670 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.670 LMU_LAL_LAUNCHER[5431:c07] 10
2012-11-11 17:15:57.671 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.671 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.671 LMU_LAL_LAUNCHER[5431:c07] 10
2012-11-11 17:15:57.672 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.672 LMU_LAL_LAUNCHER[5431:c07] 72
2012-11-11 17:15:57.672 LMU_LAL_LAUNCHER[5431:c07] 105
2012-11-11 17:15:57.673 LMU_LAL_LAUNCHER[5431:c07] 115
2012-11-11 17:15:57.673 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.673 LMU_LAL_LAUNCHER[5431:c07] 105
2012-11-11 17:15:57.673 LMU_LAL_LAUNCHER[5431:c07] 110
2012-11-11 17:15:57.674 LMU_LAL_LAUNCHER[5431:c07] 105
2012-11-11 17:15:57.674 LMU_LAL_LAUNCHER[5431:c07] 116
2012-11-11 17:15:57.674 LMU_LAL_LAUNCHER[5431:c07] 105
2012-11-11 17:15:57.675 LMU_LAL_LAUNCHER[5431:c07] 97
2012-11-11 17:15:57.675 LMU_LAL_LAUNCHER[5431:c07] 108
2012-11-11 17:15:57.675 LMU_LAL_LAUNCHER[5431:c07] 32
2012-11-11 17:15:57.675 LMU_LAL_LAUNCHER[5431:c07] 112
2012-11-11 17:15:57.676 LMU_LAL_LAUNCHER[5431:c07] 108
2012-11-11 17:15:57.676 LMU_LAL_LAUNCHER[5431:c07] 97

【问题讨论】：

可能你需要使用 stringByReplacingCharactersInRange 方法从最终字符串中删除多余的空格。
我已经尝试过completeTrimmed = [completeTrimmed stringByReplacingOccurrencesOfString:@" " withString:@""];，但它没有任何作用
@" " 之间应该有大约 15 个空格，但注释会将其自动更正为 1 个空格
您尝试过使用 stringByTrimmingCharactersInSet 吗？请检查以下答案。

标签： objective-c html-parsing

【解决方案1】：

检查一下，

  //Decode HTML entities and return
  NSString *retString = [result stringByDecodingHTMLEntities];
  [result release];

  //Drain
  [pool drain];

  retString = [[retString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] retain];

  //Return
  return [retString autorelease];   
}

如果上述方法不起作用，也可以尝试

completeTrimmed = [completeTrimmed stringByReplacingOccurrencesOfString:@"\n" withString:@""];

和

completeTrimmed = [completeTrimmed stringByReplacingOccurrencesOfString:@"\r" withString:@""];

【讨论】：

如果有帮助，源代码来自像这样的文章laloyolan.com/news/…
我正在使用正文段落
您可以尝试使用 NSLog 在控制台中打印，看看这些字符到底是什么？那么，completeTrimmed = [completeTrimmed stringByReplacingOccurrencesOfString:@"/n" withString:@""];和 completeTrimmed = [completeTrimmed stringByReplacingOccurrencesOfString:@"/r" withString:@""];
我添加了最后两行——没有变化。我会在上面发布nslog
我曾经检查过具体的空格字符是什么，我认为它返回了 char 32。让我仔细检查一下

【解决方案2】：

您可以将@"/n/n" 替换为@"/n" 以减少换行数。

【讨论】：

我试过 stringByReplacingString:@"/n/n"With:@"/n" 但没有任何改变
我意识到它不起作用，因为连续的 /n 字符被空格分隔
很高兴您发现了问题。所以你可以用“/n”替换“/n /n”

【解决方案3】：

我已经尝试过上面的问题，这就是我解决它的方法，

NSString *retString = [[result stringByDecodingHTMLEntities] retain];
[result release];

retString = [retString stripDuplicateCharactersInSet:[NSCharacterSet whitespaceCharacterSet] withString:@" "];
retString = [retString stripDuplicateCharactersInSet:[NSCharacterSet newlineCharacterSet] withString:@"\n"];

我在 NSString 上定义了一个类别方法，

- (NSString *)stripDuplicateCharactersInSet:(NSCharacterSet *)characterSet withString:(NSString *)joiningString;

实现如下，

- (NSString *)stripDuplicateCharactersInSet:(NSCharacterSet *)characterSet withString:(NSString *)joiningString {

    NSMutableString *originalStr = [NSMutableString string];

    if (!self) {
        return nil;
    }

    NSArray *componentsArray = [self componentsSeparatedByCharactersInSet:characterSet];

    int counter = 0;
    for (NSString *stringComponent in componentsArray) {

        counter ++;

        if ((stringComponent) && ([stringComponent length] > 0) && (![stringComponent isEqualToString:@" "]) && ((![stringComponent isEqualToString:@"\n"]) || (![joiningString isEqualToString:@"\n"]))) {

            if ([componentsArray count] == counter) {
                [originalStr appendFormat:@"%@", stringComponent];                
            } else {
                [originalStr appendFormat:@"%@%@", stringComponent, joiningString];
            }
        }
    }

    return originalStr;
}

在NSString+HTML.m 文件中添加上述方法作为NSString 上的一个类别。基本上在你给出的 html 中，空格和换行符被混合了多次，并且试图单独去除换行符是行不通的。因此，我通过比较字符串在剥离后是否具有换行符或空格然后附加到主字符串来删除重复的换行符和空格，如上所示。

或者，你也可以试试，

NSString *retString = [[result stringByDecodingHTMLEntities] retain];
[result release];

retString = [retString stripDuplicateNewlineCharacters];

方法定义为，

- (NSString *)stripDuplicateNewlineCharacters {

    NSMutableString *originalStr = [NSMutableString string];

    if (!self) {
        return nil;
    }

    NSArray *componentsArray = [self componentsSeparatedByCharactersInSet:[NSCharacterSet newlineCharacterSet]];

    int counter = 0;
    for (NSString *stringComponent in componentsArray) {

        counter ++;

        stringComponent = [stringComponent stringByReplacingOccurrencesOfString:@" " withString:@"<#$%$#>"];
        stringComponent = [stringComponent stringByReplacingOccurrencesOfString:@"<#$%$#><#$%$#>" withString:@"<#$%$#>"];
        stringComponent = [stringComponent stringByReplacingOccurrencesOfString:@"<#$%$#>" withString:@" "];

        if ((stringComponent) && ([stringComponent length] > 0) && (![stringComponent isEqualToString:@" "]) && (![stringComponent isEqualToString:@"\n"])) {

            if ([componentsArray count] == counter) {
                [originalStr appendFormat:@"%@", stringComponent];
            } else {
                [originalStr appendFormat:@"%@\n", stringComponent];
            }
        }
    }

    return originalStr;
}

在这种情况下，方法本身会删除重复的空格，同时删除换行符。

【讨论】：

现在是一个很长的段落。我尝试删除空格的 stripDuplicateCharacters 方法，因此只保留换行方法，结果是第 1 段后多出一行空格，第 2 段后正确间距，对于其余段落，段落从新行开始，但段落之间没有空格。
我编辑了换行符集的方法，现在所有的段落都很好，除了 1，它有 1 额外的空间。我删除了条件(![stringComponent isEqualToString:@" "])
@Mahir，这很奇怪，因为它对我来说很好用。您可以尝试在打印到控制台之前添加此 retString = [retString stringByReplacingOccurrencesOfString:@"\n" withString:@"**#NEWLINE#**"]; 并查看段落之间有多少换行符？
我也只打电话给retString = [retString stripDuplicateCharactersInSet:[NSCharacterSet newlineCharacterSet] withString:@"\n"];
不调用任何方法，模式为p1后3个换行符，剩余后2个换行符