iphone - NSURLConnection 在 UITableView 滚动之前不是 "firing"

Question

我有一个 UITableView，它异步加载图像，并在加载后将其放置在 UITableViewCell 中(我使用的代码与“LazyTableImages”教程中几乎完全相同)。当我滚动表格时，这对所有图像都适用，但它不会加载 View 中第一个图像。

代码肯定工作正常，因为实际发送 NSURLConnection 请求的类被正确调用(我添加了一个 NSLog 并且它到达了控制台)。 NSURLConnection 只是不调用委托(delegate)方法(didReceiveData、connectionDidFinishLoading 等)。

这是我的代码:

<小时/>

HomeController.m

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

    static NSString *CellIdentifier = @"Cell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

 if (cell == nil) {

        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];

  NSArray *feed = [feeds objectAtIndex: indexPath.row];

  /**
    * Name of person
   */
  [...]

  /**
    * Feed entry
   */
  [...]

  /**
    * Misc work
   */
  [...]

 }

 FeedRecord *feedRecord = [self.entries objectAtIndex:indexPath.row];

 if( !feedRecord.image ) {

  if (self.table.dragging == NO && self.table.decelerating == NO)
  {
   [self startIconDownload:feedRecord forIndexPath:indexPath];
  }

  cell.imageView.image = [UIImage imageNamed:@"Placeholder.png"];                

 }

    return cell;
 }

    - (void)startIconDownload:(FeedRecord *)feedRecord forIndexPath:(NSIndexPath *)indexPath
    {
        IconDownloader *iconDownloader = [imageDownloadsInProgress objectForKey:indexPath];
        if (iconDownloader == nil) 
        {
            iconDownloader = [[IconDownloader alloc] init];
            iconDownloader.feedRecord = feedRecord;
            iconDownloader.indexPathInTableView = indexPath;
            iconDownloader.delegate = self;
            [imageDownloadsInProgress setObject:iconDownloader forKey:indexPath];
            [iconDownloader startDownload];
            [iconDownloader release];   
        }
    }

<小时/>

IconDownload.m

#import "IconDownloader.h"
#import "FeedRecord.h"

#define kAppIconHeight 48

@implementation IconDownloader

@synthesize feedRecord;
@synthesize indexPathInTableView;
@synthesize delegate;
@synthesize activeDownload;
@synthesize imageConnection;

#pragma mark

- (void)dealloc
{
    [feedRecord release];
    [indexPathInTableView release];

    [activeDownload release];

    [imageConnection cancel];
    [imageConnection release];

    [super dealloc];
}

- (void)startDownload
{
 NSLog(@"%@ %@",@"Started downloading", feedRecord.profilePicture); // this shows in log
    self.activeDownload = [NSMutableData data];
    // alloc+init and start an NSURLConnection; release on completion/failure
    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:
                             [NSURLRequest requestWithURL:
                              [NSURL URLWithString:feedRecord.profilePicture]] delegate:self];
    self.imageConnection = conn;
 NSLog(@"%@",conn); // this shows in log
    [conn release];
}

- (void)cancelDownload
{
    [self.imageConnection cancel];
    self.imageConnection = nil;
    self.activeDownload = nil;
}


#pragma mark -
#pragma mark Download support (NSURLConnectionDelegate)

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
 NSLog(@"%@ %@",@"Got data for", feedRecord.profilePicture);
    [self.activeDownload appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
 NSLog(@"%@",@"Fail!");
 // Clear the activeDownload property to allow later attempts
    self.activeDownload = nil;

    // Release the connection now that it's finished
    self.imageConnection = nil;
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
  NSLog(@"%@ %@",@"Done", feedRecord.profilePicture);
   // Set appIcon and clear temporary data/image
    UIImage *image = [[UIImage alloc] initWithData:self.activeDownload];

 self.feedRecord.image = image;

    self.activeDownload = nil;

 [image release];

    // Release the connection now that it's finished
    self.imageConnection = nil;

 NSLog(@"%@ %@",@"Our delegate is",delegate);
    // call our delegate and tell it that our icon is ready for display
    [delegate feedImageDidLoad:self.indexPathInTableView];
}

@end

<小时/>

还有其他人经历过类似的事情或者可以识别我的代码的问题吗？谢谢!

Answer 1

您可以使用此代码

[tableView performSelector:@selector(reloadData) onThread:[NSThread mainThread] withObject:nil waitUntilDone:YES];

相反

[tableView reloadData];