objective-c之如何将 UIActivityIndicatorView 与 XML 加载一起使用

我有一个 View ，当我单击一个按钮时，我使用 TBXML 解析器从 XML 文件中获取一些内容。在单击按钮方法中看起来像这样:

// Should be [activityIndicator startAnimating]; 
NSURL *url = [NSURL URLWithString:@"adress.xml"]; 
NSData *data = [NSData dataWithContentsOfURL:url]; 
TBXML *tbxml = [TBXML newTBXMLWithXMLData:data error:nil]; 
listArray = [NSMutableArray arrayWithObjects:nil]; 
[self getData:tbxml.rootXMLElement]; 
// Should be [activityIndicator stopAnimating]; 

但是activityIndi​​cator没有显示......这不是它的实现问题，因为如果我在 View 的开头添加它就会看到它......所以我被卡住了。有什么建议吗？

非常感谢

编辑:这是代码:

我的函数，当我单击按钮时调用:

NSURL *url = [NSURL URLWithString:@"adress.xml"]; 
 
dispatch_queue_t queue = dispatch_get_global_queue( 
                                 DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); 
dispatch_async(queue, ^{ 
    NSData *data = [NSData dataWithContentsOfURL:url]; 
    dispatch_async(dispatch_get_main_queue(), ^(void) { 
        TBXML *tbxml = [TBXML newTBXMLWithXMLData:data error:nil]; 
        listArray = [NSMutableArray arrayWithObjects:nil]; 
        [self getData:tbxml.rootXMLElement]; 
        [activityIndicator stopAnimating]; 
    }); 
}); 

我的 getData 函数:

- (void) getData : (TBXMLElement *) element 
{ 
    Offre *offre = [[Offre alloc] init]; 
    do { 
        if(!go) if([[TBXML elementName:element] isEqualToString:@"item"]) go = YES; 
        if(go) 
        { 
            if([[TBXML elementName:element] isEqualToString:@"title"]) [offre set_title:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"description"]) [offre set_description:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"pubDate"]) [offre set_pubDate:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"link"]) [offre set_link:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"contract-type"]) [offre set_contractType:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"salary"]) [offre set_salary:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"fn-org"]) [offre set_fnOrg:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"locality"]) [offre set_locality:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"state"]) [offre set_state:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"filiere"]) [offre set_filiere:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"categorie"]) [offre set_categorie:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"statut"]) [offre set_statut:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"country-name"]) [offre set_countryName:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"tag"]) [offre set_tag:[TBXML textForElement:element]]; 
            if([[TBXML elementName:element] isEqualToString:@"familleMetiers"])  
            { 
                [offre set_familleMetier:[TBXML textForElement:element]]; 
                [listArray addObject:offre]; 
                offre = nil; 
            } 
        } 
        if (element->firstChild) [self getData:element->firstChild]; 
    } while ((element = element->nextSibling)); 
} 

我想知道这是否不是因为函数的递归性。

请您参考如下方法:

问题是您的 dataWithContentOfURL需要很长时间。因此，最好在后台执行此操作。你可以这样做:

NSURL *url = [NSURL URLWithString:@"adress.xml"]; 
 
dispatch_queue_t queue = dispatch_get_global_queue( 
                                 DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); 
dispatch_async(queue, ^{ 
    NSData *data = [NSData dataWithContentsOfURL:url]; 
    dispatch_async(dispatch_get_main_queue(), ^(void) { 
        TBXML *tbxml = [TBXML newTBXMLWithXMLData:data error:nil]; 
        listArray = [NSMutableArray arrayWithObjects:nil]; 
        [self getData:tbxml.rootXMLElement]; 
        [activityIndicator stopAnimating]; 
    }); 
});