去掉navigationController 中navigationBar下方的横线

//自定义一个NaVIgationBar
    [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
    //消除阴影
    self.navigationController.navigationBar.shadowImage = [UIImage new];

可以在BaseNavigationController

#import "BaseNavigationController.h"

@interface BaseNavigationController ()

@property (nonatomic,strong) UIImage * oldShadoImg;

@property (nonatomic,strong) UIImage * clearImage;

@end

@implementation BaseNavigationController

- (UIImage *)clearImage{
    if (_clearImage == nil) {
        _clearImage = [UIImage new];
    }
    return  _clearImage;
}

- (void)viewDidLoad{
    [super viewDidLoad];
    self.oldShadoImg = self.navigationBar.shadowImage;
}

- (void)HiddenNavBarLine:(BOOL)isHidden{
    if (isHidden) {
        [self.navigationBar setBackgroundImage:self.clearImage forBarMetrics:UIBarMetricsDefault];
        self.navigationBar.shadowImage = self.clearImage;
    }else{
        [self.navigationBar setBackgroundImage:self.oldShadoImg forBarMetrics:UIBarMetricsDefault];
        self.navigationBar.shadowImage = self.oldShadoImg;
    }
}





@end