统一设置导航栏的皮肤颜色

+ (void)initialize{

UINavigationBar *bar = [UINavigationBar appearance];

//    [self buttonImageFromColor:[UIColor blackColor]]

UIImage *image = [UIImage imageNamed:@"img_nav_topbar"];

[bar setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];

// 设置uibarbuttonitem统一为白色

UIBarButtonItem *item = [UIBarButtonItem appearance];

NSMutableDictionary *attributes = [NSMutableDictionary dictionary];

attributes[NSForegroundColorAttributeName] = [UIColor whiteColor];

[item setTitleTextAttributes:attributes forState:UIControlStateNormal];

// 设置导航栏返回按钮的颜色

[bar setTintColor:[UIColor whiteColor]];

// 导航栏设置黑色后，标题设置白色

NSMutableDictionary *dic = [NSMutableDictionary dictionary];

dic[NSForegroundColorAttributeName] = [UIColor whiteColor];

[bar setTitleTextAttributes:dic];

}