您可以将其添加到窗口中
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
UIView *backgrView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] bounds].size.width, [[UIScreen mainScreen] bounds].size.height)];
backgrView.backgroundColor = [UIColor blackColor];
backgrView.alpha = 0.6;
[[appDelegate window] addSubview:backgrView];
或者
Try navigationBar.translucent = NO; , It is YES by default in iOS7.
So you can add a version check like this:
float systemVersion = [[[UIDevice currentDevice] systemVersion] floatValue];
if (systemVersion >= 7.0)
{
navigationBar.translucent = NO;
}