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我有一個UITableView異步加載圖像，並將其放置在UITableViewCell一旦它被加載（我使用幾乎完全相同的代碼，在「LazyTableImages」教程）。當我滾動表格時，這對所有圖像都適用，但不會加載視圖中第一個圖像。NSURLConnection不是「射擊」，直到UITableView滾動
代碼肯定工作正常，因爲實際發送NSURLConnection請求的類被正確調用（我添加了NSLog並且它到達了控制檯）。 NSURLConnection只是不調用委託方法（didReceiveData，connectionDidFinishLoading等）。
這裏是我的代碼：
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];
}
}
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
是否有其他人遇到類似這樣的事情，或者可以識別我的代碼問題？謝謝！
都能跟得上。我得到的代碼將初始化請求並立即開始下載URL。 （該方法的Apple文檔：「返回初始化的URL連接並開始加載URL請求的數據。」）。 [NSURLConnection start]也不起作用:( – Simon 2010-06-09 09:15:50
對不起，我誤讀了文檔，實際上我看不到你的代碼存在問題，你是否在startDownload方法中設置了斷點，並檢查是否一切正常？ – Alfonso 2010-06-09 14:55:17