异步图像下载 [英] Async image downloader

问题描述

我有写一点类通过使用NSURLConnection的进行图像的下载。
这个想法是到下载委托给这个类来避免阻塞执行。

I have write a little class to perform the download of the images by using an NSURLConnection. The idea it's to delegate the download to this class to avoid to block the execution.

所以我传递目标的UIImageView（由参）和URL的功能和开始下载：

So I pass the target UIImageView (by ref) and the url to the function and start the download:

-(void)getImage:(UIImageView**)image formUrl:(NSString*)urlStr
{
    NSLog(@"Downloader.getImage.url.debug: %@",urlStr);
    NSURL *url = [NSURL URLWithString:urlStr];
    NSURLRequest *req = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:5.0];
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    NSURLConnection *c = [[NSURLConnection alloc] initWithRequest:req delegate:self];
    [conn addObject:c];
    int i = [conn indexOfObject:c];
    [imgs insertObject:*image atIndex:i];
    [c release];
}

当它完成设置图像和更新ImageView的：

When it's finished set the image and update the imageView:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    int i = [conn indexOfObject:connection];

    NSData *rawData = [buffer objectAtIndex:i];
    UIImage *img = [UIImage imageWithData:rawData];
    UIImageView *imgView = [imgs objectAtIndex:i];
    imgView.image = img;

    [imgView setNeedsDisplay];

    [conn removeObjectAtIndex:i];
    [imgs removeObjectAtIndex:i];
    [buffer removeObjectAtIndex:i];

    if ([conn count]==0) {
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
    }
}

该系统的工作原理相当不错，但我不能得到更新的UIImageView一个UITableViewCell的细胞内部，任何想法？ （实际上是细胞，当我点击它，它的更新）
还有就是要实现这个功能更好的方法？ （实际上需要有：无阻塞，缓存系统）

This system works quite good, but i can't get updated the UIImageView inside the cells of a UITableViewCell, any idea ? (actually the cell it's updated when I click on it) There is a better way to implement this functionality ? (actually the need are: non-blocking, caching system)

推荐答案

塞萨尔

有关异步图像加载，缓存和线程操作，我使用SDImageCache类从 http://github.com/rs/SDWebImage。我也写了我自己的几次，但是这一次是辉煌的，我已经抛出所有我的老code了。

For async image loading, caching and threaded operation, I use SDImageCache class from http://github.com/rs/SDWebImage. I also wrote my own several times, but this one is brilliant and I've thrown all my old code away.

从它的文档：

只是＃进口的的UIImageView + WebCache.h 头，并调用 setImageWithURL ：placeholderImage：从的tableView方法：的cellForRowAtIndexPath： UITableViewDataSource方法。一切都会为你处理，从异步下载到缓存管理。

Just #import the UIImageView+WebCache.h header, and call the setImageWithURL:placeholderImage: method from the tableView:cellForRowAtIndexPath: UITableViewDataSource method. Everything will be handled for you, from async downloads to caching management.

希尔顿

这篇关于异步图像下载的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！