subview load from xib,reload view frame, but viewsubviews not change frame

• (void)viewDidLoad {

  self.buttonSubView=(EventbuttonsView *)[[NSBundle mainBundle] loadNibNamed:@"ActionHeadView" owner:nil options:nil][1];

  [self.buttonSubView setY:self.view.frame.size.height-130];

  [self.buttonSubView setWidth:self.view.frame.size.width];

  self.buttonSubView.backgroundColor=[UIColor redColor];

  [self.view addSubview:self.buttonSubView];

  [self.buttonSubView layoutIfNeeded];

}

buttonSubView is a customview, It's subviews use autolayout , when i call [self.buttonSubView layoutIfNeeded], but subviews donot update frame? why? in xib i use update frame, it is ok.but run in iPhone,cannot work?