NSScanner 可在 WiFi 上工作，但不能在 3G 上工作

Question

我已经设置了一个 NSScanner，可以通过点击 UIButton 来工作，代码如下：

-(IBAction)doLoadTTData
{

NSString *Period1String = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"Period1String" ofType: @"txt"] usedEncoding:nil error:nil];
NSString *Period2String = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"Period2String" ofType: @"txt"] usedEncoding:nil error:nil];
NSString *Period3String = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"Period3String" ofType: @"txt"] usedEncoding:nil error:nil];
NSString *Period4String = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"Period4String" ofType: @"txt"] usedEncoding:nil error:nil];
NSString *Period5String = [NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource: @"Period5String" ofType: @"txt"] usedEncoding:nil error:nil];

NSURL *currentURL = [NSURL URLWithString:webView.request.URL.absoluteString];
NSLog(@"Loaded Timetable");
NSError *loaderror;
NSString *page = [NSString stringWithContentsOfURL:currentURL 
                                          encoding:NSASCIIStringEncoding
                                             error:&loaderror];

[webView loadHTMLString:page baseURL:currentURL];

NSString *Period1Data = nil;

NSScanner *htmlScanner =  [NSScanner scannerWithString:page];

[htmlScanner scanUpToString:Period1String intoString:NULL];
[htmlScanner scanString:Period1String intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&Period1Data];

NSLog(@"Collected Period 1 Data: %@", Period1Data);

if(Period1Data == NULL)
{

    Period1Data = @"Not Available";
    [period1label setText:@"Not Available"];

}

else if(Period1Data == @"(null)")
{

    Period1Data = @"Not Available";
    [period1label setText:@"Not Available"];

}

else

{

    [period1label setText:Period1Data];

}

NSString *Period2Data = nil;

[htmlScanner scanUpToString:Period2String intoString:NULL];
[htmlScanner scanString:Period2String intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&Period2Data];

if(Period2Data == NULL)
{

    Period2Data = @"Not Available";
    [period2label setText:@"Not Available"];

}

else if(Period2Data == @"(null)")
{

    Period2Data = @"Not Available";
    [period2label setText:@"Not Available"];

}

else

{

    [period2label setText:Period2Data];
    [period2label setText:@"Not Available"];

}

NSLog(@"Collected Period 2 Data: %@", Period2Data);

NSString *Period3Data = nil;

[htmlScanner scanUpToString:Period3String intoString:NULL];
[htmlScanner scanString:Period3String intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&Period3Data];

if(Period3Data == NULL)
{

    Period3Data = @"Not Available";
    [period3label setText:@"Not Available"];

}

else if(Period3Data == @"(null)")
{

    Period3Data = @"Not Available";
    [period3label setText:@"Not Available"];

}

else

{

    [period3label setText:Period3Data];

}

NSLog(@"Collected Period 3 Data: %@", Period3Data);

NSString *Period4Data = nil;

[htmlScanner scanUpToString:Period4String intoString:NULL];
[htmlScanner scanString:Period4String intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&Period4Data];

if(Period4Data == NULL)
{

    Period4Data = @"Not Available";
    [period4label setText:@"Not Available"];

}

else if(Period4Data == @"(null)")
{

    Period4Data = @"Not Available";
    [period4label setText:@"Not Available"];

}

else

{

    [period4label setText:Period4Data];

}

NSLog(@"Collected Period 4 Data: %@", Period4Data);

NSString *Period5Data = nil;

[htmlScanner scanUpToString:Period5String intoString:NULL];
[htmlScanner scanString:Period5String intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&Period5Data];

if(Period5Data == NULL)
{

    Period5Data = @"Not Available";
    [period5label setText:@"Not Available"];

}

else if(Period5Data == @"(null)")
{

    Period5Data = @"Not Available";
    [period5label setText:@"Not Available"];

}

else

{

    [period5label setText:Period5Data];

}

NSLog(@"Collected Period 5 Data: %@", Period5Data);

NSString* TimetableDate = nil;
NSString *DateString = [NSString stringWithFormat:@"<FONT size=2>&nbsp;<STRONG><FONT size=3>"];

[htmlScanner scanUpToString:DateString intoString:NULL];
[htmlScanner scanString:DateString intoString:NULL];
[htmlScanner scanUpToString:@"</FONT>" intoString:&TimetableDate];

NSString *timetablefulldate = [NSString stringWithFormat:@"Timetable for %@", TimetableDate];

[timetabledate setText:timetablefulldate];

[TimetableLoading setHidden:YES];
[TimetableLoadingBG setHidden:YES];


if(Period1Data == NULL && Period2Data == NULL && Period3Data == NULL && Period4Data == NULL && Period5Data == NULL)
{

    if(ttbacking.tag == 10)

    {

        NSLog(@"Already showing message");

    }

    else

    {

        UIAlertView *message = [[UIAlertView alloc] initWithTitle:@"Timetable"
                                                          message:@"Looks like you don't have any lessons today! Maybe you'd like to get some homework out of the way?"
                                                         delegate:nil
                                                cancelButtonTitle:@"I'll have a think"
                                                otherButtonTitles:nil];

        [message show];

        [ttbacking setTag:10];

    }

    [period1label setText:@"Free Time"];
    [period2label setText:@"Free Time"];
    [period3label setText:@"Free Time"];
    [period4label setText:@"Free Time"];
    [period5label setText:@"Free Time"];

    period1backing.image = [UIImage imageNamed:@"redperiodbacking.png"];
    period2backing.image = [UIImage imageNamed:@"redperiodbacking.png"];
    period3backing.image = [UIImage imageNamed:@"redperiodbacking.png"];
    period4backing.image = [UIImage imageNamed:@"redperiodbacking.png"];
    period5backing.image = [UIImage imageNamed:@"redperiodbacking.png"];

}

if(TimetableDate == NULL)
{

    [timetabledate setText:@"No timetable today"];

}

[prevDay setHidden:NO];
[nextDay setHidden:NO];

NSLog(@"Student Timetable collected and published");

}

不幸的是，这只适用于 WiFi，不适用于 3G。

如果我在 3G 连接上按下按钮，所有标签都会显示“不可用”，因为结果为“NULL”。这很奇怪，因为我一次将 UIWebView 放在所有内容的前面来测试页面是否实际加载，并且确实加载了，就像在 WiFi 上一样。由于某些原因，NSScanner 无法在 3G 上运行。

为什么会这样呢？只要告诉我您是否需要查看其他代码...

Answer 1

我有几件事要说。首先，你用扫描仪之类的东西所做的事情确实很hacky。如果您尝试解析 HTML，则应该以正确的方式进行。使用诸如 libxml2（iPhone 内置）之类的东西来实际解析 html 并从中获取内容。老实说，您的系统可能会因小更新或页面故障而崩溃。

咆哮已经够多了，但是如果您决定保留当前系统，您可以尝试从当前加载的页面中检索实际的 html。

例如（正如我已经在您的其他问题中发布的那样）：

NSString *path = @"document.body.innerHTML";
NSString *html = [webView stringByEvaluatingJavaScriptFromString:path];

由于您的网络视图可以加载，那么您应该能够像这样从加载的网络视图中获取内容。

如果我可以补充一下，这是行不通的：else if(Period1Data == @"(null)")。调试器打印 (null)，但如果字符串为 null，则它永远不会显示为 (null)。如果你要比较字符串，你会做 isEqualToString:，但我正在逃避自己。 ;)