iPhone 异步加载图片

AsyncImageView.h文件

@interface AsyncImageView : UIView {
    NSURLConnection* connection;
    NSMutableData* data;
}
@end

AsyncImageView.m文件

 

@implementation AsyncImageView
 
- (void)loadImageFromURL:(NSURL*)url {
    if (connection!=nil) { [connection release]; }
    if (data!=nil) { [data release]; }
    NSURLRequest* request = [NSURLRequest requestWithURL:url
             cachePolicy:NSURLRequestUseProtocolCachePolicy
             timeoutInterval:60.0];
    connection = [[NSURLConnection alloc]
             initWithRequest:request delegate:self];
    //TODO error handling, what if connection is nil?
}
 
- (void)connection:(NSURLConnection *)theConnection
     didReceiveData:(NSData *)incrementalData {
    if (data==nil) {
          data =
          [[NSMutableData alloc] initWithCapacity:2048];
    }
    [data appendData:incrementalData];
}
 
- (void)connectionDidFinishLoading:(NSURLConnection*)theConnection {
 
    [connection release];
    connection=nil;
 
    if ([[self subviews] count]>0) {
        [[[self subviews] objectAtIndex:0] removeFromSuperview];
    }
 
    UIImageView* imageView = [[[UIImageView alloc] initWithImage:[UIImage imageWithData:data]] autorelease];
 
    imageView.contentMode = UIViewContentModeScaleAspectFit;
    imageView.autoresizingMask = ( UIViewAutoresizingFlexibleWidth || UIViewAutoresizingFlexibleHeight );
 
    [self addSubview:imageView];
    imageView.frame = self.bounds;
    [imageView setNeedsLayout];
    [self setNeedsLayout];
    [data release];
    data=nil;
}
 
- (UIImage*) image {
    UIImageView* iv = [[self subviews] objectAtIndex:0];
    return [iv image];
}
 
- (void)dealloc {
    [connection cancel];
    [connection release];
    [data release];
    [super dealloc];
}
 
@end

在tableview中具体使用

- (UITableViewCell *)tableView:(UITableView *)tableView
       cellForRowAtIndexPath:(NSIndexPath *)indexPath {
 
    static NSString *CellIdentifier = @"ImageCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
 
    if (cell == nil) {
        cell = [[[UITableViewCell alloc]
              initWithFrame:CGRectZero reuseIdentifier:CellIdentifier]
              autorelease];
    } else {
	AsyncImageView* oldImage = (AsyncImageView*)
             [cell.contentView viewWithTag:999];
	[oldImage removeFromSuperview];
    }
 
	CGRect frame;
	frame.size.width=75; frame.size.height=75;
	frame.origin.x=0; frame.origin.y=0;
	AsyncImageView* asyncImage = [[[AsyncImageView alloc]
               initWithFrame:frame] autorelease];
	asyncImage.tag = 999;
	NSURL* url = [imageDownload
               thumbnailURLAtIndex:indexPath.row];
	[asyncImage loadImageFromURL:url];
 
	[cell.contentView addSubview:asyncImage];
 
    return cell;
}