去掉 NavigationBar 底部的那条黑线

转载自: http://code4app.com/snippets/one/%E5%8E%BB%E6%8E%89-NavigationBar-%E5%BA%95%E9%83%A8%E7%9A%84%E9%82%A3%E6%9D%A1%E9%BB%91%E7%BA%BF/5315f43e933bf0473e8b5db3#s0

1
2

[[ UINavigationBar appearance ] setBackgroundImage :[[ UIImage alloc ] init ] forBarMetrics :UIBarMetricsDefault];
[[ UINavigationBar appearance ] setShadowImage :[[ UIImage alloc ] init ]];