from:http://blog.sina.com.cn/s/blog_4adf31ea0100qvp1.html
-(void) action: (UIBarButtonItem *) item
{
loadingview = [[UIAlertView alloc] initWithTitle:nil
//创建等待图标
UIActivityIndicatorView *activityView = [[UIActivityIndicatorView alloc]initWithActivityIndicato
activityView.frame = CGRectMake(120.f, 48.0f, 37.0f, 37.0f);
[loadingview addSubview:activityView];
[activityView startAnimating];
[activityView release];
[loadingview show];
[NSThread detachNewThreadSelector:@selector(CloseLoading) toTarget:selfwithObject:nil];
}
-(void) CloseLoading
{
//等待3秒
[NSThread sleepForTimeInterval:3];
//删除等待视图
[loadingview dismissWithClickedButton
}