設置的UILabel的背景顏色會導致應用程序崩潰

Question

我有以下代碼：

UIImageView *photo = [[[UIImageView alloc] initWithFrame:CGRectMake(title_bar.titleView.frame.origin.x+130, title_bar.titleView.frame.origin.y-12, 22.0, 22.0)] autorelease]; 
UIImage *theImage = [UIImage imageNamed:@"question mark icon"]; 
photo.image = theImage; 
UIView *new_view = [[UIView alloc] init]; 
[new_view addSubview:photo]; 
UILabel *new_label = [[UILabel alloc] initWithFrame:CGRectMake(title_bar.titleView.frame.origin.x-145, title_bar.titleView.frame.origin.y-12, 268.0, 22.0)]; 
[new_label setText:@"gregrgtg"]; 
[new_label setBackgroundColor:[UIColor clearColor]]; //COMMENTING THIS LINE OUT MAKES IT WORK 
[new_view addSubview:new_label]; 
title_bar.titleView = new_view; 

當背景色設置爲清除，該程序SIGABRTs。如果我將該行註釋掉，它可以正常工作（除了標籤的背景只是白色）。另外，如果我只是初始化標籤而不是initWithFrame，那麼程序不會崩潰，但我的標籤不可見。

Answer 1

UIImageView *photo = [[[UIImageView alloc] initWithFrame:CGRectMake(title_bar.titleView.frame.origin.x+130, title_bar.titleView.frame.origin.y-12, 22.0, 22.0)] autorelease]; 
UIImage *theImage = [UIImage imageNamed:@"question mark icon"]; 
photo.image = theImage; 
UIView *new_view = [[UIView alloc] init]; 
[new_view addSubview:photo]; 

title_bar.titleView = new_view;//this line by madhu 

UILabel *new_label = [[UILabel alloc] initWithFrame:CGRectMake(title_bar.titleView.frame.origin.x-145, title_bar.titleView.frame.origin.y-12, 268.0, 22.0)]; 
[new_label setText:@"gregrgtg"]; 
[new_label setBackgroundColor:[UIColor clearColor]]; //COMMENTING THIS LINE OUT MAKES IT WORK 
[new_view addSubview:new_label]; 

原因：

ü又增加了烏爾標題欄的titleview的atlast但在此之前提到它們。