在Fragment中使用CustomDelegate的setDelegate报NullPointerException

[jingzhanwu]

sheet = new SweetSheet(mRootView);
CustomDelegate customDelegate = new CustomDelegate(true, CustomDelegate.AnimationType.DuangLayoutAnimation);
View mSheetView = LayoutInflater.from(getActivity()).inflate(R.layout.disc_near_shop_bottom_sheet, null, false);
customDelegate.setCustomView(mSheetView);
sheet.setDelegate(customDelegate);