Android 安卓4.0标签滑动导致崩溃

我添加了一个新活动，并将其设置为导航类型中的选项卡滑动。 到目前为止还不错，但当我滑动到另一个选项卡时，它崩溃并给出了这个错误（但它至少显示了布局）：

切换选项卡：

@Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a DummySectionFragment (defined as a static inner class
            // below) with the page number as its lone argument.
            Fragment fragment = null;           
            switch (position) {
            case 0:
                fragment = new AddExpense();
                break;
            case 1:
                fragment = new AddIncomeSource();
                break;
            default:
                break;
            }
            return fragment;
        }

选项卡的内部类（每个选项卡的每个类）：

---

你确定位置永远不会超过1吗？我猜是你的碎片制造开关/箱子出错了。尝试将一个片段添加到默认值中，看看崩溃是否消失。很抱歉延迟重播，非常感谢！问题是我的开关盒和你说的一模一样，所以我添加了一个默认片段。

@Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a DummySectionFragment (defined as a static inner class
            // below) with the page number as its lone argument.
            Fragment fragment = null;           
            switch (position) {
            case 0:
                fragment = new AddExpense();
                break;
            case 1:
                fragment = new AddIncomeSource();
                break;
            default:
                break;
            }
            return fragment;
        }

public static class AddExpense extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        public static final String ARG_SECTION_NUMBER = "section_number";

        public AddExpense() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

            View v = inflater.inflate(R.layout.add_expense, null);
            return v;
        }
    }

    public static class AddIncomeSource extends Fragment {
        public static final String ARG_SECTION_NUMBER = "section_number";

        public AddIncomeSource() {
        }
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {

            View v = inflater.inflate(R.layout.add_income, null);
            return v;
        }
    }