Lazytableimages не загружается на пользовательской ячейке раскадровки

Question

Я пытаюсь загрузить Ленивый Tableview в пользовательской ячейке в раскадровке, но вид таблицы выглядит пустым:

Это исходный код:

LazyLoadTable.m

#import "CellData.h" 
#import "LazyLoadTableView.h" 
#import "CustomCell.h" 
#import "ParseOperation.h" 
#import "ImageDownloader.h" 
#define kCustomRowHeight 157 
#define kCustomRowCount  1 

static NSString *const xmlDataUrl = 
@"http://itunes.apple.com/us/rss/topfreeapplications/limit=300/xml"; 

@interface LazyLoadTableView() 

@end 

@implementation LazyLoadTableView 
@synthesize tableElements; 
@synthesize queue; 
@synthesize connection; 
@synthesize xmlData; 
@synthesize tView; 
@synthesize imageDownloadsInProgress; 

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 
     // Custom initialization 

     self.tableElements=[[NSMutableArray alloc] init]; 
     self.imageDownloadsInProgress = [NSMutableDictionary dictionary]; 



    } 
    return self; 
} 


- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 


    self.title=@"Menu"; 
    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:xmlDataUrl]]; 
    self.connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self]; 

    // Test the validity of the connection object. 
    NSAssert(self.connection != nil, @"Failure to create URL connection."); 

    // show in the status bar that network activity is starting 
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; 

} 


    - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
    { 
     int count = [tableElements count]; 

     // ff there's no data yet, return enough rows to fill the screen 
     if (count == 0) 
     { 
      return kCustomRowCount; 
     } 
     return count; 
    } 


    - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
    { 
     // customize the appearance of table view cells 


     static NSString *placeholderCellIdentifier = @"PlaceholderCell"; 

     // add a placeholder cell while waiting on table data 
     int nodeCount = [self.tableElements count]; 

     if (nodeCount == 0 && indexPath.row == 0) 
     { 
      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:placeholderCellIdentifier]; 
      if (cell == nil) 
      { 
       cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle 
               reuseIdentifier:placeholderCellIdentifier]; 
       cell.detailTextLabel.textAlignment = NSTextAlignmentCenter ; 
       cell.selectionStyle = UITableViewCellSelectionStyleNone; 
      } 

      cell.detailTextLabel.text = @"Loading…"; 

      return cell; 
     } 


     static NSString *CustomCellIdentifier = @"CustomCellIdentifier"; 




     CustomCell *cell = (CustomCell *)[tableView dequeueReusableCellWithIdentifier:CustomCellIdentifier]; 
     if (cell == nil) { 
      NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"CustomCell" owner:self options:nil]; 
      for (id oneObject in nib) if ([oneObject isKindOfClass:[CustomCell class]]) 
       cell = (CustomCell *) [nib objectAtIndex:0]; 
     } 
     // Leave cells empty if there's no data yet 
     if (nodeCount > 0) 
     { 
      // Set up the cell... 
      CellData *cellData = (self.tableElements)[indexPath.row]; 

      cell.name.text = cellData.name; 


      // Only load cached images; defer new downloads until scrolling ends 
      if (!cellData.icon) 
      { 
       if (self.tView.dragging == NO && self.tView.decelerating == NO) 
       { 
        [self startIconDownload:cellData forIndexPath:indexPath]; 
       } 
       // if a download is deferred or in progress, return a placeholder image 




       cell.itemImage.image = [UIImage imageNamed:@"Placeholder.png"]; 
      } 
      else 
      { 
       cell.itemImage.image = cellData.icon; 
      } 

     } 


     return cell; 
    } 

    - (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { 
     return kCustomRowHeight; 

    } 




    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{ 
    self.xmlData = [NSMutableData data]; // start off with new data 
} 


- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
{ 
    [self.xmlData appendData:data]; // append incoming data 
} 
#pragma mark - 
#pragma mark NSURLConnection delegate methods 

- (void)handleError:(NSError *)error 
{ 
    NSString *errorMessage = [error localizedDescription]; 
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Cannot Show Data" 
                 message:errorMessage 
                 delegate:nil 
               cancelButtonTitle:@"OK" 
               otherButtonTitles:nil]; 
    [alertView show]; 
} 

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 
{ 
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; 

    if ([error code] == kCFURLErrorNotConnectedToInternet) 
    { 
     // if we can identify the error, we can present a more precise message to the user. 
     NSDictionary *userInfo = @{NSLocalizedDescriptionKey: @"No Connection Error"}; 
     NSError *noConnectionError = [NSError errorWithDomain:NSCocoaErrorDomain 
                 code:kCFURLErrorNotConnectedToInternet 
                userInfo:userInfo]; 
     [self handleError:noConnectionError]; 
    } 
    else 
    { 
     // otherwise handle the error generically 
     [self handleError:error]; 
    } 

    self.connection = nil; // release our connection 
} 


- (void)connectionDidFinishLoading:(NSURLConnection *)connection 
{ 
    self.connection = nil; // release our connection 

    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; 

    // create the queue to run our ParseOperation 
    self.queue = [[NSOperationQueue alloc] init]; 
    ParseOperation *operation = [[ParseOperation alloc] initWithData:self.xmlData delegate:self]; 

    [queue addOperation:operation]; // this will start the "ParseOperation" 



    self.xmlData = nil; 
} 
- (void)didFinishParsing:(NSArray *)cellDataList 
{ 
    [self performSelectorOnMainThread:@selector(handleLoadedApps:) withObject:cellDataList waitUntilDone:NO]; 

    self.queue = nil; // we are finished with the queue and our ParseOperation 
} 

- (void)parseErrorOccurred:(NSError *)error 
{ 
    [self performSelectorOnMainThread:@selector(handleError:) withObject:error waitUntilDone:NO]; 
} 
- (void)handleLoadedApps:(NSArray *)loadedCellData 
{ 
    [self.tableElements addObjectsFromArray:loadedCellData]; 

    // tell our table view to reload its data, now that parsing has completed 
    [self.tView reloadData]; 
} 


// Override to allow orientations other than the default portrait orientation. 
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { 
    // Return YES for supported orientations 
    return YES; 
} 

- (void)didReceiveMemoryWarning 
{ 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 


- (void)startIconDownload:(CellData *)cellData forIndexPath:(NSIndexPath *)indexPath 
{ 
    ImageDownloader *imageDownloader = imageDownloadsInProgress[indexPath]; 
    if (imageDownloader == nil) 
    { 
     imageDownloader = [[ImageDownloader alloc] init]; 
     imageDownloader.cellData = cellData; 
     imageDownloader.indexPathInTableView = indexPath; 
     imageDownloader.delegate = self; 
     imageDownloadsInProgress[indexPath] = imageDownloader; 
     [imageDownloader startDownload]; 
    } 
} 

// this method is used in case the user scrolled into a set of cells that don't have their app icons yet 
- (void)loadImagesForOnscreenRows 
{ 
    if ([self.tableElements count] > 0) 
    { 
     NSArray *visiblePaths = [self.tView indexPathsForVisibleRows]; 
     for (NSIndexPath *indexPath in visiblePaths) 
     { 
      CellData *cellData = (self.tableElements)[indexPath.row]; 

      if (!cellData.icon) // avoid the app icon download if the app already has an icon 
      { 
       [self startIconDownload:cellData forIndexPath:indexPath]; 
      } 
     } 
    } 
} 

// called by our ImageDownloader when an icon is ready to be displayed 
- (void)imageDidLoad:(NSIndexPath *)indexPath 
{ 
    ImageDownloader *imageDownloader = imageDownloadsInProgress[indexPath]; 
    if (imageDownloader != nil) 
    { 
     CustomCell *cell = (CustomCell *)[self.tView cellForRowAtIndexPath:imageDownloader.indexPathInTableView]; 

     // Display the newly loaded image 
     cell.itemImage.image = imageDownloader.cellData.icon; 
    } 
} 


#pragma mark - 
#pragma mark Deferred image loading (UIScrollViewDelegate) 

// Load images for all onscreen rows when scrolling is finished 
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate 
{ 
    if (!decelerate) 
    { 
     [self loadImagesForOnscreenRows]; 
    } 
} 

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView 
{ 
    [self loadImagesForOnscreenRows]; 
} 



@end 

CustomCel п.м.

#import "CustomCell.h" 

@implementation CustomCell 

@synthesize itemImage; 

@synthesize name; 


- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier 
{ 
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]; 
    if (self) { 
     // Initialization code 
    } 
    return self; 
} 

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

    // Configure the view for the selected state 
} 

@end 

Answer 1

Не читал через весь код, но это выглядит, как вы пытаетесь ленивым загрузить изображение с текстом. Я очень рекомендую использовать SDWebImage для ленивой загрузки. Это просто и очень просто настроить.