去掉导航栏下 细线

    //去除bar下方 线
    if ([self.navigationController.navigationBar respondsToSelector:@selector( setBackgroundImage:forBarMetrics:)]){
        NSArray *list=self.navigationController.navigationBar.subviews;
        for (id obj in list) {
            if ([obj isKindOfClass:[UIImageView class]]) {
                UIImageView *imageView=(UIImageView *)obj;
                NSArray *list2=imageView.subviews;
                for (id obj2 in list2) {
                    if ([obj2 isKindOfClass:[UIImageView class]]) {
                        UIImageView *imageView2=(UIImageView *)obj2;
                        imageView2.hidden=YES;
                    }
                }
            }
        }
    }

2、iOS10出来之后，@"_UINavigationBarBackground" 变成了@"_UIBarBackground"，代码改成这样：

#define iOS10 ([[UIDevice currentDevice].systemVersion intValue]>=10?YES:NO)
- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];

    [self.navigationController.navigationBar.subviews enumerateObjectsUsingBlock:^(UIView *view, NSUInteger idx, BOOL *stop) {
        if (iOS10) {
            //iOS10,改变了导航栏的私有接口为_UIBarBackground
            if ([view isKindOfClass:NSClassFromString(@"_UIBarBackground")]) {

                [view.subviews firstObject].hidden = YES;
            }
        }else{
            //iOS10之前使用的是_UINavigationBarBackground
            if ([view isKindOfClass:NSClassFromString(@"_UINavigationBarBackground")]) {

                [view.subviews firstObject].hidden = YES;
            }
        }
    }];
}








可不可以精简一下呢：

如果设置了
[UINavigationBar appearance].translucent = NO;

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];

    self.navigationController.navigationBar.subviews[0].subviews[0].hidden = YES;
}
否则

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];

    self.navigationController.navigationBar.subviews[0].subviews[1].hidden = YES;
}