How to download multiple images of table view cell in background? - iphone

Question

i want to create an application in one row of tableView there will be 4 images of button which will be loaded from server in background because if i directly load them than the table view will hang some. for this i have used this code for creating button in cell and performing to download images in background.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *hlCellID = #"hlCellID";
UITableViewCell *hlcell = [tableView dequeueReusableCellWithIdentifier:hlCellID];
if(hlcell == nil) {
hlcell = [[[UITableViewCell alloc]
initWithStyle:UITableViewCellStyleDefault reuseIdentifier:hlCellID] autorelease];
hlcell.accessoryType = UITableViewCellAccessoryNone;
hlcell.selectionStyle = UITableViewCellSelectionStyleNone;
}
int section = indexPath.section;
NSMutableArray *sectionItems = [sections objectAtIndex:section];
int n = [sectionItems count];
int i = 0, j = 0, tag = 1;
int x = 10;
int y = 30;
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
for (i = 1; i<= n ; i++) //[arr count]
{
for(j=1; j<=4;j++)
{
if (i>=n) break;
Item *item = [sectionItems objectAtIndex:i];
CGRect rect = CGRectMake(x = x, y = y, 68, 65);
UIButton *button=[[UIButton alloc] initWithFrame:rect];
[button setFrame:rect];
UIImage *buttonImageNormal=[UIImage imageNamed:item.image];
[button setBackgroundImage:buttonImageNormal forState:UIControlStateNormal];
[button setContentMode:UIViewContentModeCenter];
// set the image to be loaded (using the same one here but could/would be different)
NSURL *imgURL = [NSURL URLWithString:#"http://londonwebdev.com/wp-content/uploads/2010/07/featured_home.png"];
// Create an array with the URL and imageView tag to
// reference the correct imageView in background thread.
NSMutableArray *arr = [[NSArray alloc] initWithObjects:imgURL, [NSString stringWithFormat:#"%d", tag], nil ];
// Start a background thread by calling method to load the image
[self performSelectorInBackground:#selector(loadImageInBackground:) withObject:arr];
// button.tag = [tagValue intValue];
button.tag = tag;
//NSLog(#"....tag....%d", button.tag);
[button addTarget:self action:#selector(buttonPressed:) forControlEvents:UIControlEventTouchUpInside];
[hlcell.contentView addSubview:button];
[button release];
tag++;
x = x + 77;
}
x = 10;
y = y + 74;
}
[pool release];
return hlcell;
}
the above code work perfectly but when i download the images and trying to assign at the some particular button than i can't find the button tags althoug i can find the button tags while touchupinside action.
- (void) loadImageInBackground:(NSArray *)urlAndTagReference {
NSLog(#"Received URL for tagID: %#", urlAndTagReference);
// Create a pool
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
// Retrieve the remote image. Retrieve the imgURL from the passed in array
NSData *imgData = [NSData dataWithContentsOfURL:[urlAndTagReference objectAtIndex:0]];
UIImage *img = [[UIImage alloc] initWithData:imgData];
// Create an array with the URL and imageView tag to
// reference the correct imageView in background thread.
NSMutableArray *arr = [[NSArray alloc] initWithObjects:img, [urlAndTagReference objectAtIndex:1], nil ];
// Image retrieved, call main thread method to update image, passing it the downloaded UIImage
[self performSelectorOnMainThread:#selector(assignImageToImageView:) withObject:arr waitUntilDone:YES];
[pool release];
}
- (void) assignImageToImageView:(NSArray *)imgAndTagReference
{
// Create a pool
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
int i;
UIButton *checkView;
// [imagesForCategories addObject:[imgAndTagReference objectAtIndex:1]];
// UITableViewCell *cell = [celebCategoryTableView cellForRowAtIndexPath:[imgAndTagReference objectAtIndex:1]];
// UIImageView *profilePic = (UIImageView *)[cell.contentView viewWithTag:20];
// profilePic.image = [imgAndTagReference objectAtIndex:0];
// checkView.tag = [[imgAndTagReference objectAtIndex:1] intValue];
// loop
for (UIButton *checkView in [self.tblImage subviews] )
{ i++;
NSLog(#"Checking tag: %d against passed in tag %d",checkView.tag, [[imgAndTagReference objectAtIndex:1] intValue]);
if ([checkView tag] == [[imgAndTagReference objectAtIndex:1] intValue]) {
if (i==35) break;
// Found imageView from tag, update with img
// [checkView setImage:[imgAndTagReference objectAtIndex:0]];
[checkView setImage:[imgAndTagReference objectAtIndex:0] forState:UIControlStateNormal];
//set contentMode to scale aspect to fit
checkView.contentMode = UIViewContentModeScaleAspectFit;
//change width of frame
CGRect frame = checkView.frame;
frame.size.width = 80;
checkView.frame = frame;
}
}
// release the pool
[pool release];
// Remove the activity indicator created in ViewDidLoad()
[self.activityIndicator removeFromSuperview];
}
the all code works perfect but i can't find the table cell subview here for (UIButton *checkView in [self.tblImage subviews] so how to find the subviews of table cell subviews.?
i want to create something like this pls see image.! after that new city will come and just section change the data will show new images in row and cell section.

Answer 1

you may use SDWebImage
Web Image
This library provides a category for UIImageVIew with support for remote images coming from the web.
It provides:
An UIImageView category adding web image and cache management to the Cocoa Touch framework
An asynchronous image downloader
An asynchronous memory + disk image caching with automatic cache expiration handling
A guarantee that the same URL won't be downloaded several times
A guarantee that bogus URLs won't be retried again and again
Performances!
just use it
[youImageView setImageWithURL:[NSURL URLWithString:url] placeholderImage:nil options:SDWebImageRetryFailed];