iOS NavigationBar 透明

#OC

```

[self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];

[self.navigationController.navigationBar setShadowImage:[UIImage new]];[self.navigationController.navigationBar setTranslucent:YES];

```

#Swift

```

self.navigationController?.navigationBar.setBackgroundImage(UIImage(),forBarMetrics: UIBarMetrics.Default)

self.navigationController?.navigationBar.shadowImage = UIImage()

self.navigationController?.navigationBar.translucent = true

```