UIView递归

 

（UITextField *）findFirstResponder:(UIView *) view{

    //遍历子视图

    for(UIView *child in view.subviews){

        if([child responesToSelector:@selector(isFirstResponder)] && [child isFirstResponder]){

            return (UITextField *) child;

        }

     //子控件的第一响应者

    UITextField *field = [self findFirstResponder: child];

     if(field){

       return field;

    }

   }

}