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我尝试以编程方式创建 HTML 文件。但生成的文件显示为空白文件。我不知道这个问题。

这是我的代码：

- (IBAction) createFileAction
{
    NSLog(@"************* createFileAction *************");
    NSMutableString *htmlString = [[NSMutableString alloc] init];
    NSLog(@"%@",htmlString);
    [htmlString appendString:@"<html><head><title></title><style type='text/css'>.style1{height: 27px;}#Text1{height: 19px;width: 210px;}.style2{width: 255px;}.style3{height: 27px;width: 255px;}#petValue{width: 206px;}#nameValue{width: 206px;}#dateValue{width: 209px;}"];
    [htmlString appendString:@"#Text2{width: 215px;}#Text3{width: 210px;height: 22px;}#Text4{width: 209px;}.style8{width: 13px;}.style9{ width: 263px;}.style10{height: 27px;width: 263px;}"];
    [htmlString appendString:@".style11{width: 418px;}.style12{width: 199px;}.style13{height: 27px; width: 199px;}.style14{height: 24px;}.style15{width: 410px;}</style> </head>"];
    [htmlString appendString:@"<body>"];

    NSString *originalString = [NSString stringWithContentsOfURL:[NSURL URLWithString:@"http://www.makepartsfast.com/2012/09/4337/more-3d-printing-in-metals-ex-one-introduces-the-m-flex-3d-printing-system/"] encoding:NSUTF8StringEncoding error:nil];
    NSScanner *scanner = [NSScanner scannerWithString:originalString];
    NSString *extractedString = nil;


    [scanner scanUpToString:@"<div class=\"postarea\">" intoString:nil];
    [scanner scanString:@"<div class=\"postarea\">" intoString:nil];



    [scanner scanUpToString:@"<div style=\"clear:both;\">" intoString:&extractedString];


    if (extractedString) 
    {
        // string was extracted
        NSLog(@"%@", extractedString);
    }   
    NSLog(@"BEFORE= %@",htmlString);
    [htmlString appendString:extractedString];
     NSLog(@"AFTER= %@",htmlString);
    [htmlString appendString:@"</body></html>"];
    NSLog(@"FINAL=%@",htmlString);

    // check to see if file already exists in documents directory
    if([self.fileMgr fileExistsAtPath:self.file])
    {
        NSLog(@"File already exists");
    }
    else 
    {
        NSLog(@"file does not exist");
        NSLog(@"Try creating the file");

        // file does not already exist so create it
        [self.fileMgr createFileAtPath:file contents:nil attributes:nil];

        NSLog(@"%@",htmlString);
        [htmlString writeToFile:self.file atomically:NO encoding:NSStringEncodingConversionAllowLossy error:nil];


        //Test again whether this file exists now that we have tried creating it
        if([self.fileMgr fileExistsAtPath:self.file])
        {
            NSLog(@"File exists now");
        }
        else 
        {
            NSLog(@"File still doesn't exist");
        }

    }
}

在这种方法中，我只从 html 格式的提取字符串中的 URL 中选择部分并将其附加到 htmlstring。当我尝试附加不同的字符串时，它工作正常。

4

1 回答 1

5

NSStringEncodingConversionAllowLossy这是因为您作为encoding参数传递。您应该传递字符串编码参数之一。发生的事情是NSStringEncodingConversionAllowLossy等于 1。但是writeToFile:atomically:encoding:error:期待一个字符串编码常量。等于 1 的字符串编码常量是NSASCIIStringEncoding. 但是您的字符串无法转换为 ASCII，因此您得到一个空文件。将该行更改为使用 UTF8，您将获得预期的非空文件：

[htmlString writeToFile:self.file atomically:NO encoding:NSUTF8StringEncoding error:nil];

至少部分原因是您没有检查返回类型或错误条件，因此您遇到了麻烦。方法调用返回，如果出现任何问题BOOL，将创建一个。NSError如果您在听，这将帮助您找出问题所在。如果你这样做了：

NSError *saveError = nil;
if (![htmlString writeToFile:file atomically:NO encoding:NSStringEncodingConversionAllowLossy error:&saveError]) {
    NSLog(@"Error writing file: %@", saveError);
}

您会看到一条错误消息，内容如下：

2012-11-21 11:20:47.250 Untitled[5731:707] Error writing file: Error Domain=NSCocoaErrorDomain Code=517 "The file “junk.html” couldn’t be saved using text encoding Western (ASCII)." UserInfo=0x7ffc0860b7c0 {NSFilePath=/tmp/junk.html, NSStringEncoding=1

起初这可能并不明显，但它特别提到尝试使用 ASCII 的事实将是问题根源的一个巨大线索。

于 2012-11-21T18:25:59.437 回答