更改UITextField和UIButton字体名称，UIAlertView的颜色

Question

我想将我的UITextField字体名称和UIButton（取消，确定）颜色更改为AlertView的黑色。 但它并没有改变我的预期。

- (IBAction)newGroup:(id)sender{
    self.alertView = [[UIAlertView alloc] initWithTitle:@"" message:@"새 그룹의 이름을 입격" delegate:self cancelButtonTitle:@"취소" otherButtonTitles:@"확인", nil];
    self.alertView.tag = new_group;
    self.alertView.alertViewStyle = UIAlertViewStylePlainTextInput;
    [self.alertView show];
}

//自定义字体名称，UIAlertView控件的颜色

- (void)willPresentAlertView:(UIAlertView)alertView{
  if(alertView.tag == new_group){
    for(UIView *subView in alertView){
       if([subView isKindOfClass:[UIButton class]]){
         UIButton *button = (UIButton *)subView;
         button.titleLabel.textColor = [UIColor blackColor];
       }else if([subView isKindOfClass:[UITextField class]]){
         UITextField *textView = (UITextField *)subView;
         textView.font = [UIFont fontWithName:@"Helvetica" size:30.0f];
       }
    }
  }
}

UITextField字体名称和字体大小，UIButton（取消，确定）在默认情况下看起来仍然相同。