改变Alert的背景图片
UIAlertView *theAlert = [[[UIAlertView alloc] initWithTitle:@"Atention"
message: @"XXXXX!"
delegate:nil
cancelButtonTitle:@"Cancel"
otherButtonTitles:@"Okay",nil] autorelease];
[theAlert show];
UIImage *theImage = [UIImage imageNamed:@"XXX.png"];
theImage = [theImage stretchableImageWithLeftCapWidth:0. topCapHeight:0.];
CGSize theSize = [theAlert frame].size;
UIGraphicsBeginImageContext(theSize);
[theImage drawInRect:CGRectMake(0, 0, theSize.width, theSize.height)];
theImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
theAlert.layer.contents = (id)[theImage CGImage];