更改AlertView背景

UIAlertView *theAlert = [[[UIAlertViewalloc] initWithTitle:@"Atention"  
                                                     message: @"I'm a Chinese!"  
                                                    delegate:nil   
                                            cancelButtonTitle:@"Cancel"   
                                            otherButtonTitles:@"Okay",nil] autorelease];  
   [theAlert show];  
   UIImage *theImage = [UIImageimageNamed:@"loveChina.png"];     
   theImage = [theImage stretchableImageWithLeftCapWidth:0topCapHeight:0];  
   CGSize theSize = [theAlert frame].size;  
    UIGraphicsBeginImageContext(theSize);      
   [theImage drawInRect:CGRectMake(5, 5, theSize.width-10, theSize.height-20)];// 这个地方的大小要自己调整，以适应 alertview 的背景颜色的大小。  
   theImage = UIGraphicsGetImageFromCurrentImageContext();     
UIGraphicsEndImageContext();  
   theAlert.layer.contents = (id)[theImage CGImage];