DataBaseHelper getRow错误

Question

行。简单的背景。 Activity启动Fragment1，它加载从数据库（getAllRows）提供的名称列表视图。当我从Fragment1中选择一个名称时，每个名称都有我想要加载到Fragment2中的相关信息。但是，当我进行选择并在Fragment2中调用getRow以便将信息加载到listView中进行显示时，它会出错。我无法弄清楚什么是错的。

片段1

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

    openDB();

    View rootView = inflater.inflate(R.layout.list_view, container, false);

    myList = (ListView) rootView.findViewById(R.id.list);

    Cursor cursor = myDB.getAllRows();

    String[] fromFieldNames = new String[]
            {DataBaseHelper.KEY_NAME};

    int[] toViewIDs = new int[]
            {R.id.elListText};

    SimpleCursorAdapter myCursorAdapter =
            new SimpleCursorAdapter(
                    rootView.getContext(),
                    R.layout.el_list_item,
                    cursor,
                    fromFieldNames,
                    toViewIDs
                    );

    myList.setAdapter(myCursorAdapter);

    myList.setOnItemClickListener(new ItemClickListener());

    return rootView;
}

public class ItemClickListener implements ListView.OnItemClickListener {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selectElement(position);
    }
}

// selectElement Method
// passes the information from the selected element
// into the elementFragment fragment

public void selectElement(int position) {

    Cursor c = myDB.getRow(++position);
    Fragment fragment = new elementFragment();
    Bundle args = new Bundle();

    // define arguments to provide to next fragment
    args.putInt(elementFragment.ARG_ELEMENT_NUMBER, position);

    fragment.setArguments(args);

    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction().replace(table.periodic.R.id.content_frame, fragment).commit();
    closeDB();


}

Fragment2

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

    openDB();

    View viewElement = inflater.inflate(R.layout.list_view_element, container, false);

    viewList = (ListView) viewElement.findViewById(R.id.list_view);

    Bundle args = getArguments();

    int i = args.getInt(elementFragment.ARG_ELEMENT_NUMBER);

40      Cursor c = myDB.getRow(i);


    String[] fromFieldNames = new String[]
            {DataBaseHelper.KEY_NAME};

    int[] toViewIDs = new int[]{
            R.id.elRowDesc
    };

    SimpleCursorAdapter myCursorAdapter =
            new SimpleCursorAdapter(
                    viewElement.getContext(),
                    R.layout.el_list_item,
                    c,
                    fromFieldNames,
                    toViewIDs
                    );

    viewList.setAdapter(myCursorAdapter);

    String name = args.getString(DataBaseHelper.KEY_NAME);

    getActivity().setTitle(name);

    return viewElement;
}

DataBaseHelper

    public Cursor getRow(int rowId) {
    String where = KEY_ROWID + "=" + rowId;
168     Cursor c = myDataBase.query(true, DB_TABLE, ALL_KEYS, 

            where, null, null, null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;
}

logcat的

10-24 12:07:07.864: E/AndroidRuntime(29534): FATAL EXCEPTION: main
10-24 12:07:07.864: E/AndroidRuntime(29534): java.lang.NullPointerException
10-24 12:07:07.864: E/AndroidRuntime(29534):    at table.periodic.DataBaseHelper.getRow(DataBaseHelper.java:168)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at table.periodic.elementFragment.onCreateView(elementFragment.java:40)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.Fragment.performCreateView(Fragment.java:1785)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:887)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1059)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.BackStackRecord.run(BackStackRecord.java:682)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1437)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.os.Handler.handleCallback(Handler.java:725)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.os.Handler.dispatchMessage(Handler.java:92)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.os.Looper.loop(Looper.java:158)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at android.app.ActivityThread.main(ActivityThread.java:5751)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at java.lang.reflect.Method.invokeNative(Native Method)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at java.lang.reflect.Method.invoke(Method.java:511)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850)
10-24 12:07:07.864: E/AndroidRuntime(29534):    at dalvik.system.NativeStart.main(Native Method)