detachNewThreadSelector 使应用程序随机崩溃

Question

我正在开发一个 iPhone 应用程序，在其中提取 RSS 提要然后解析它们。我的代码如下：

 - (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    NSLog(@"in view did appear");

    if ([stories count] == 0) {
        NSString * path = @"http://www.shire.com/shireplc/rss.jsp";

        //[self parseXMLFileAtURL:path];
        //[self performSelectorInBackground:@selector(parseXMLFileAtURL:) withObject:path];
        NSLog(@"internet is %d",[self checkInternet]);
        if([self checkInternet]==1)
        [NSThread detachNewThreadSelector:@selector(parseXMLFileAtURL:) 
                              toTarget:self withObject:path];

}
}

 - (void)parseXMLFileAtURL:(NSString *)URL
  { 
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
  stories = [[NSMutableArray alloc] init];

  //you must then convert the path to a proper NSURL or it won't work
  NSURL *xmlURL = [NSURL URLWithString:URL];

  // here, for some reason you have to use NSClassFromString when trying to alloc NSXMLParser, otherwise you will get an object not found error
  // this may be necessary only for the toolchain
  rssParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];

  // Set self as the delegate of the parser so that it will receive the parser delegate methods callbacks.
[rssParser setDelegate:self];

// Depending on the XML document you're parsing, you may want to enable these features of NSXMLParser.
[rssParser setShouldProcessNamespaces:NO];
[rssParser setShouldReportNamespacePrefixes:NO];
[rssParser setShouldResolveExternalEntities:NO];

[rssParser parse];

 [pool release];

}

谁能告诉我哪里出错了？ 我的日志如下： 日志：[切换到线程12803] [切换到线程12035] 2011-05-10 11:31:30.932 年报[454:490b] 找到文件并开始解析 [切换到线程14339] 2011-05-10 11:32:04.742 年报[454:640b] 找到文件并开始解析 [切换到线程13827] [切换到线程13827] 程序收到信号：“EXC_BAD_ACCESS”。

gdb stack trace at 'putpkt: write failed':
0   gdb-arm-apple-darwin                0x0019026b remote_backtrace_self + 54

Answer 1

我不确定，但我猜该方法的参数会在某个时刻被释放。您能否确保该 URL 存在于方法 parseXMLFileAtURL 中

Answer 2

最后，我使用一个标志来检查视图是否出现（通过在 viewdidAppear 中将标志设置为 true），如果视图没有出现，则不要运行线程函数。这解决了问题！

Answer 3

// 你可以使用该方法，如果你不必更新UserInterface，这会更安全。

 [self performSelectorInBackground:@selector(parseXMLFileAtURL:) withObject:path];

如果UserInterface也需要更新，你可以先在后台解析数据，然后用方法更新ui。

[self performSelectorOnMainThread:@selector(myUpdateUI) withObject:nil waitUntilDone:YES];