下载图片时的进度条

Question

如何添加进度条来下载大图或任何文件？这里是我的代码：

NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, 
                  NSUserDomainMask, YES); 

     NSString *docsPath = [paths objectAtIndex:0]; 
     NSString *downloadPath = [[[NSString alloc]initWithFormat:@"http://www.zzz.com/%@.jpg",chartFileName]autorelease]; 
     NSString *savePath = [[[NSString alloc]initWithFormat:@"%@/%@.jpg",docsPath, chartFileName]autorelease]; 
     NSURL *url = [[NSURL alloc]initWithString:downloadPath]; 
     NSData *downloadedChartData = [NSData dataWithContentsOfURL:url]; 
     [url release]; 
     [downloadedChartData writeToFile:savePath atomically:YES]; 

Answer 1

你可以覆盖连接：didReceiveData：在你的NSURLConnection调用中。请参阅此处了解更多：

How to integrate NSURLConnection with UIProgressView?

Answer 2

在后台运行一个选择器，检查图像的下载大小，并将其与所需大小进行比较。然后将进度条的％设置为已下载/需要。