ios - 使用afnetworking拉JSON时显示加载动画

我正在尝试使用MBProgressHUD来弹出加载动画，同时该应用程序加载更多json数据。这是我用来调用包含MBProgressHUD的函数的代码。

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
float bottomEdge = scrollView.contentOffset.y + scrollView.frame.size.height;
if (bottomEdge >= scrollView.contentSize.height) {
    pageCounter++;


    [MBProgressHUD showHUDAddedTo:self.view animated:YES];
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 0.01 * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        // Do something...
        [self loadAdditionalJson];
        [MBProgressHUD hideHUDForView:self.view animated:YES];
    });

    }
}

这就是所谓的函数：

-(void)loadAdditionalJson

{

NSLog(@"%i", pageCounter);
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:
                                   @"http://ragetracks.com/?json=1&count=50&page=%i&custom_fields=PostThumb&include=title,content,attachments",
                                   pageCounter]];


NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {

    for (int x = 0; x < 50; x++) {
        //NSLog(@"%i", pageCounter*50 -50 + x);
        if ([JSON[@"posts"][x][@"attachments"] count] == 0)
        {
            NSString *temp = [NSURL URLWithString:@"nothing"];
            [imageUrls addObject:temp];
        }
        else
        {
            NSString *temp1;
            //temp1 = [NSString stringWithFormat:@"%@", JSON[@"posts"][x][@"id"]];
            //NSLog(temp1);
            NSURL *imageUrl =  [NSURL URLWithString:
                                [NSString stringWithFormat:@"%@",
                                JSON[@"posts"][x][@"attachments"][0][@"images"][@"medium"][@"url"]]];
           NSString *title = [NSString stringWithFormat:@"%@", JSON[@"posts"][x][@"title"]];

            NSString *label = [NSString stringWithFormat:@"%@", JSON[@"posts"][x][@"content"]];

            NSScanner *scanner = [NSScanner scannerWithString:label];
            [scanner scanUpToString:@"%2Ftracks%2F" intoString:nil];
            [scanner scanString:@"%2Ftracks%2F" intoString:nil];
            [scanner scanUpToString:@"&" intoString:&temp1];

            NSURL *temp2 = [NSURL URLWithString:[NSString stringWithFormat:@"https://api.soundcloud.com/tracks/%@.json?client_id=7622aa84a50c9f7609e2f7ed8bc85e81", temp1]];

            if (imageUrl) {
                [imageUrls addObject:imageUrl];
            }
            else{
                NSString *temp = [NSURL URLWithString:@"nothing"];
                [imageUrls addObject:temp];
            }
            [titles addObject:title];
            [contentUrls addObject:temp2];

        }
    }
    [self.collectionView reloadData];

} failure:nil];


    [operation start];
}

加载动画只会出现和消失得太快，并不能反映应用程序加载新信息所花费的时间。我知道这与主线程有关，但是我不确定该怎么做。我尝试关闭AFNetworkActivityIndicatorManager，但这似乎没有任何影响。使系统进入睡眠状态会延迟它，但是仍然无法正确反映加载时间，因为进入睡眠状态后，系统会返回并完成加载。

最佳答案

好吧，您要求它...在启动JSON加载之前，您延迟了很短的时间（这似乎毫无意义），然后在启动加载后立即关闭进度指示器。

我认为您的困惑在于您认为JSON加载是同步完成的-但事实并非如此。

因此，删除：

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 0.01 * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

因为它没有帮助您。启动HUD动画后，只需开始加载即可。然后，在处理JSON的成功块（在JSONRequestOperationWithRequest上）中，在扫描代码之后，添加：

[MBProgressHUD hideHUDForView:self.view animated:YES];

如果应该在[self.collectionView reloadData];之后继续。