全局设置导航栏背景色：
// 设置状态栏颜色
[UIApplication sharedApplication].statusBarStyle = UIStatusBarStyleLightContent;
// 设置全局UINavigationBar背景色
UINavigationBar*bar = [UINavigationBar appearance];
CGFloat rgb =0.1;
bar.barTintColor= [UIColor colorWithRed:rgb green:rgb blue:rgb alpha:0.9];
bar.tintColor= [UIColor whiteColor];
bar.titleTextAttributes=@{NSForegroundColorAttributeName: [UIColor whiteColor]};
