UITabBarItem's appearance

1.我们知道，用tabBarController创建出来默认的tabBar似这个样子滴。。。

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2.通常通过appearance统一设置，可以一劳永逸，不必在每个控制器设置

@implementation TTTabBarController

+(void)initialize{
    
    //normal状态的文字属性
    NSMutableDictionary *attrDic = [[NSMutableDictionary alloc]init];
    [attrDic setValue:[UIColor grayColor] forKey:NSForegroundColorAttributeName];
    [attrDic setValue:[UIFont systemFontOfSize:] forKey:NSFontAttributeName];
    
    //select状态的文字属性
    NSMutableDictionary *selectedAttrDic = [[NSMutableDictionary alloc]init];
    [selectedAttrDic setValue:[UIColor darkGrayColor] forKey:NSForegroundColorAttributeName];
    [selectedAttrDic setValue:[UIFont systemFontOfSize:] forKey:NSFontAttributeName];
    
    //项目中所有tabBarItem都将是这种文字状态
    UITabBarItem *item = [UITabBarItem appearance];
    [item setTitleTextAttributes:attrDic forState:UIControlStateNormal];//normal状态
    [item setTitleTextAttributes:selectedAttrDic forState:UIControlStateSelected];//select状态
}

效果如下：