设置navigationBar透明,隐藏iOS导航条底部与self.view的分界线

[[[self.navigationController.navigationBar subviews] firstObject] setAlpha:0];

隐藏iOS导航条底部与self.view的分界线

[self.navigationController.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];
self.navigationController.navigationBar.shadowImage = [[UIImage alloc] init];