android setLayoutParams 问题，出错

1             LinearLayout layt = (LinearLayout) rootView.findViewById(R.id.llt_2);
2             FrameLayout.LayoutParams layoutParams=new FrameLayout.LayoutParams(FrameLayout.LayoutParams.WRAP_CONTENT, FrameLayout.LayoutParams.WRAP_CONTENT);
3             layoutParams.gravity=Gravity.CENTER;            
4             layt.setLayoutParams(layoutParams);