更改UITabBar的字体颜色 与 状态栏的样式

1.更改tabbar的字体的颜色：

 [[UITabBarItem appearance]setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor whiteColor],NSForegroundColorAttributeName, nil] forState:(UIControlStateSelected)];

2.设置状态栏的样式:

 [UIApplication sharedApplication].statusBarStyle = UIStatusBarStyleLightContent;