我是 Xcode 的新手，对UIProgressView. 我找到了一些代码，但我不太明白。你能解释一下为什么UIProgressView完成后不关闭吗？
- (IBAction)Download:(id)sender
{
NSURL *url = [NSURL URLWithString:@"http://db.tt/5WP2pia"];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
progressView = [[UIProgressView alloc]
initWithFrame:CGRectMake(30.0f, 80.0f, 225.0f, 90.0f)];
UIAlertView *progressAlert =
[[UIAlertView alloc] initWithTitle: @"Download..."
message: @"Please wait..."
delegate: self
cancelButtonTitle: nil
otherButtonTitles: nil];
[progressAlert addSubview:progressView];
[progressView setProgressViewStyle: UIProgressViewStyleBar];
[request setDownloadDestinationPath:@"/var/root/osk.rar"];
[request setDownloadProgressDelegate:progressView];
[progressAlert show];
[progressAlert release];
}