使用UIActivityIndi​​catorView的活动指示器（微调器） [英] Activity indicator (spinner) with UIActivityIndicatorView

问题描述

我有一个tableView加载XML feed，如下：

I have a tableView that loads an XML feed as follows:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    if ([stories count] == 0) {
        NSString *path = @"http://myurl.com/file.xml";
        [self parseXMLFileAtURL:path];
    }
}

我想让微调器显示

I'd like to have the spinner to show on the top bar at the app launch and dissapear once the data is displayed on my tableView.

我认为将开头放在viewDidAppear，结束于 - （void）parserDidEndDocument：（NSXMLParser *）parser 但它不工作。

I thought that putting the beginning at viewDidAppear and the end at -(void)parserDidEndDocument:(NSXMLParser *)parser but it didn't work.

如何实现此解决方案。

推荐答案

这里有问题： NSXMLParser 同步API。这意味着，一旦你在你的 NSXMLParser 上调用 parse ，那个线程将完全停滞解析xml，

Here's the problem: NSXMLParser is a synchronous API. That means that as soon as you call parse on your NSXMLParser, that thread is going to be totally stuck parsing xml, which means no UI updates.

以下是我通常解决这个问题的方法：

Here's how I usually solve this:

- (void) startThingsUp {
  //put the spinner onto the screen
  //start the spinner animating

  NSString *path = @"http://myurl.com/file.xml";
  [self performSelectorInBackground:@selector(parseXMLFileAtURL:) withObject:path];
}

- (void) parseXMLFileAtURL:(NSString *)path {
  //do stuff
  [xmlParser parse];
  [self performSelectorOnMainThread:@selector(doneParsing) withObject:nil waitUntilDone:NO];
}

- (void) doneParsing {
  //stop the spinner
  //remove it from the screen
}

我已经多次使用这个方法了，它的工作原理很好。

I've used this method many times, and it works beautifully.

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