外观代理仅影响新初始化视图的外观。在外观代理上设置颜色不会对已经可见的导航栏产生影响。

The appearance proxy only affects the look of newly initialized views. Setting colors on the appearance proxy will have no effect on navigation bars that are already visible.

您需要手动更新当前视图；例如：

You'll need to manually update your current view; for example:

self.navigationController.navigationBar.barTintColor = [UINavigationBar appearance].barTintColor;