• 1.自定义导航控制器

• 2.重写自定义导航控制器的initialize类方法

  • 因为该类在第一次使用导航控制器的使用，正符合，因为主题也只需要设置一次

• 3.代码实现

/**
 * 当第一次使用这个类的时候会调用一次
 */
+ (void)initialize
{
    // 当导航栏用在XMGNavigationController中, appearance设置才会生效
//    UINavigationBar *bar = [UINavigationBar appearanceWhenContainedIn:[self class], nil];
    UINavigationBar *bar = [UINavigationBar appearance];
    [bar setBackgroundImage:[UIImage imageNamed:@"navigationbarBackgroundWhite"] forBarMetrics:UIBarMetricsDefault];
    [bar setTitleTextAttributes:@{NSFontAttributeName : [UIFont boldSystemFontOfSize:20]}];

    // 设置item
    UIBarButtonItem *item = [UIBarButtonItem appearance];
    // UIControlStateNormal
    NSMutableDictionary *itemAttrs = [NSMutableDictionary dictionary];
    itemAttrs[NSForegroundColorAttributeName] = [UIColor blackColor];
    itemAttrs[NSFontAttributeName] = [UIFont systemFontOfSize:17];
    [item setTitleTextAttributes:itemAttrs forState:UIControlStateNormal];
    // UIControlStateDisabled
    NSMutableDictionary *itemDisabledAttrs = [NSMutableDictionary dictionary];
    itemDisabledAttrs[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
    [item setTitleTextAttributes:itemDisabledAttrs forState:UIControlStateDisabled];
}