iOS开发笔记--异步加载图片在TableView中的应用

//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;
}

转自： http://blog.sina.com.cn/s/blog_7f7a975b01017szx.html