Setting UILabel background color causes app to crash

问题

I have the following code:

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;

When the background color is set to clear, the program SIGABRTs. If I comment out that line, it works fine (except that the background for the label is just white). Also, if I just init the label rather than initWithFrame-ing it, the program doesn't crash, but my label can't be seen.

回答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];

reason :

u had added ur titlebar's titleview atlast but referred them before .

来源：https://stackoverflow.com/questions/6625822/setting-uilabel-background-color-causes-app-to-crash