Android 使用SQLite游标适配器在片段中填充ListView

在片段上填充ListView时，我在运行代码时遇到问题。我在我的主要活动课上制作了3个片段。问题是我想在片段上创建一个ListView，然后显示它。问题是代码没有运行（查看catlog）。任何人都知道为什么：

public class DocumentItemFragment extends Fragment {

    private OnFragmentInteractionListener mListener;

    public DocumentItemFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        populateListView();
        return inflater.inflate(R.layout.fragment_document_item, container, false);
    }


    private void populateListView() {
        SQLiteHelper sqlh = new SQLiteHelper(getActivity().getBaseContext());
        SQLiteDatabase db = sqlh.getWritableDatabase();

        String query = "SELECT  * FROM invdokg";
        Cursor cursor = db.rawQuery(query, null);

        String[] fromFieldNames = new String[]
        {SQLiteHelper.KEY_ID,SQLiteHelper.KEY_NAZIV, SQLiteHelper.KEY_DATUM};

        int[] toViewIDs = new int[]
        {R.id.docItemId, R.id.docItemNaziv,R.id.docItemDate};
        SimpleCursorAdapter myCursorAdapter;

        myCursorAdapter = new SimpleCursorAdapter(getActivity().getBaseContext(), R.layout.docitem_layout, cursor, fromFieldNames, toViewIDs, 0);
        ListView myList = (ListView) getActivity().findViewById(R.id.docListView);
        myList.setAdapter(myCursorAdapter);
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener = null;
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated to
     * the activity and potentially other fragments contained in that activity.
     * <p>
     * See the Android Training lesson <a href=
     * "http://developer.android.com/training/basics/fragments/communicating.html"
     * >Communicating with Other Fragments</a> for more information.
     */
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        public void onFragmentInteraction(Uri uri);
    }

}

公共类DocumentItemFragment扩展了片段{
私有OnFragmentInteractionListener mListener；
公共文档ItemFragment（）{
//必需的空公共构造函数
}
@凌驾
创建视图上的公共视图（布局、充气机、视图组容器、，
Bundle savedInstanceState）{
//为该碎片膨胀布局
populateListView（）；
返回充气机。充气（R.layout.fragment\u document\u item，容器，假）；
}
私有void populateListView（）{
SQLiteHelper sqlh=新的SQLiteHelper（getActivity（）.getBaseContext（））；
SQLiteDatabase db=sqlh.getWritableDatabase（）；
String query=“从invdokg中选择*”；
Cursor Cursor=db.rawQuery（查询，空）；
字符串[]fromFieldNames=新字符串[]
{SQLiteHelper.KEY\u ID，SQLiteHelper.KEY\u NAZIV，SQLiteHelper.KEY\u DATUM}；
int[]toViewIDs=新int[]
{R.id.docItemId，R.id.docItemNaziv，R.id.docItemDate}；
SimpleCursorAdapter myCursorAdapter；
myCursorAdapter=新的SimpleCursorAdapter（getActivity（）.getBaseContext（），R.layout.docitem_布局，光标，fromFieldNames，toViewId，0）；
ListView myList=（ListView）getActivity（）.findViewById（R.id.docListView）；
设置适配器（myCursorAdapter）；
}
//TODO:重命名方法、更新参数并将方法挂接到UI事件中
public void onButtonPressed（Uri）{
if（mListener！=null）{
onFragmentInteraction（uri）；
}
}
@凌驾
公共事务主任（活动）{
超级转速计（活动）；
试一试{
mListener=（OnFragmentInteractionListener）活动；
}catch（ClassCastException e）{
抛出新的ClassCastException（activity.toString（）
+“必须实现OnFragmentInteractionListener”）；
}
}
@凌驾
公共无效连接（）{
super.onDetach（）；
mListener=null；
}
/**
*此接口必须由包含以下内容的活动实现
*片段以允许与此片段中的交互进行通信
*活动以及该活动中可能包含的其他片段。
*
*有关更多信息，请参阅Android培训课程。
*/
FragmentInteractionListener上的公共接口{
//TODO:更新参数类型和名称
公共void onFragmentInteraction（Uri）；
}
}

我的主要活动是：

public class MainActivity extends Activity 
implements BlankFragment.OnFragmentInteractionListener,
ExportImportFragment.OnFragmentInteractionListener,
            HistoryFragment.OnFragmentInteractionListener{
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    // nav drawer title
    private CharSequence mDrawerTitle;

    // used to store app title
    private CharSequence mTitle;

    // slide menu items
    private String[] navMenuTitles;
    private TypedArray navMenuIcons;

    private ArrayList<NavDrawerItem> navDrawerItems;
    private NavDrawerListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(this);
        //String userTheme = settings.getString("pref_key_apptheme_list", "Theme_Dark");


        mTitle = mDrawerTitle = getTitle();

        // load slide menu items
        navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

        // nav drawer icons from resources
        navMenuIcons = getResources()
                .obtainTypedArray(R.array.nav_drawer_icons);

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

        navDrawerItems = new ArrayList<NavDrawerItem>();

        // adding nav drawer items to array
        // InvDokG
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
        // ImportExport
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
        // History
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1), true, "22")); 

        // Recycle the typed array
        navMenuIcons.recycle();

        mDrawerList.setOnItemClickListener(new SlideMenuClickListener());

        // setting the nav drawer list adapter
        adapter = new NavDrawerListAdapter(getApplicationContext(),
                navDrawerItems);
        mDrawerList.setAdapter(adapter);

        // enabling action bar app icon and behaving it as toggle button
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
                R.drawable.ic_drawer, //nav menu toggle icon
                R.string.app_name, // nav drawer open - description for accessibility
                R.string.app_name // nav drawer close - description for accessibility
        ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                // calling onPrepareOptionsMenu() to show action bar icons
                invalidateOptionsMenu();
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                // calling onPrepareOptionsMenu() to hide action bar icons
                invalidateOptionsMenu();
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            // on first time display view for first nav item
            displayView(0);
        }


        // SQL Lite**********************************************************************************       
        SQLiteHelper db = new SQLiteHelper(this);

        /**
         * CRUD Operations
         * */
        // add Books
        db.addInvDokG(new InvDokG("Android Application Development Cookbook", new Date()));   
        db.addInvDokG(new InvDokG("Android Programming: The Big Nerd Ranch Guide", new Date()));       
        db.addInvDokG(new InvDokG("Learn Android App Development", new Date()));

        // get all invdokgs
        List<InvDokG> list = db.getAllInvDokGs();

        // delete one invdokg
        db.deleteInvDokG(list.get(0));

        // get all invdokgs
        db.getAllInvDokGs();
    }

    /**
     * Slide menu item click listener
     * */
    private class SlideMenuClickListener implements
            ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            // display view for selected nav drawer item
            displayView(position);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // toggle nav drawer on selecting action bar app icon/title
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action bar actions click
        Intent intent;
        switch (item.getItemId()) {
        case R.id.action_settings:
            intent = new Intent(this, SettingsActivity.class);
            startActivity(intent);
            return true;
        case R.id.action_about:
            intent = new Intent(this, AboutActivity.class);
            startActivity(intent);
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    /* *
     * Called when invalidateOptionsMenu() is triggered
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // if nav drawer is opened, hide the action items
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    /**
     * Diplaying fragment view for selected nav drawer list item
     * */
    private void displayView(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        switch (position) {
        case 0:
//          Intent i = new Intent(getBaseContext(), ItemListActivity.class);                      
//          //i.putExtra("key", value); //Optional parameters
//          startActivity(i);
            fragment = new BlankFragment();
            break;
        case 1:
            fragment = new ExportImportFragment();
            break;
        case 2:
            fragment = new HistoryFragment();
            break;
        default:
            break;
        }

        if (fragment != null) {
            FragmentTransaction transaction=getFragmentManager().beginTransaction();
            transaction.replace(R.id.frame_container,fragment);
            transaction.addToBackStack(null);
            transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            transaction.commit();

            // update selected item and title, then close the drawer
            mDrawerList.setItemChecked(position, true);
            mDrawerList.setSelection(position);
            setTitle(navMenuTitles[position]);
            mDrawerLayout.closeDrawer(mDrawerList);
        } else {
            // error in creating fragment
            Log.e("MainActivity", "Error in creating fragment");
        }
    }

    @Override
    public void setTitle(CharSequence title) {
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    /**
     * When using the ActionBarDrawerToggle, you must call it during
     * onPostCreate() and onConfigurationChanged()...
     */

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggls
        mDrawerToggle.onConfigurationChanged(newConfig);
    }

    @Override
    public void onFragmentInteraction(Uri uri) {
        // TODO Auto-generated method stub

    }
}

公共类MainActivity扩展活动
实现BlankFragment.OnFragmentInteractionListener，
ExportImportFragment.OnFragmentInteractionListener，
HistoryFragment.OnFragmentInteractionListener{
私人抽屉布局mDrawerLayout；
私有列表视图mDrawerList；
私有操作bardrawertoggle mDrawerToggle；
//导航抽屉标题
私有字符序列mDrawerTitle；
//用于存储应用程序标题
私有字符序列mTitle；
//幻灯片菜单项
私有字符串[]navMenuTitles；
专用型雷达导航仪；
私人ArrayList NavWrites；
专用导航适配器；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
//SharedReferences设置=PreferenceManager.GetDefaultSharedReferences（此）；
//String userTheme=settings.getString（“pref_key_apptheme_list”，“Theme_Dark”）；
mTitle=mDrawerTitle=getTitle（）；
//加载幻灯片菜单项
navMenuTitles=getResources（）.getStringArray（R.array.nav\u抽屉\u项目）；
//参考资料中的导航抽屉图标
navMenuIcons=getResources（）
.obtainTypedArray（R.array.nav_drawer_图标）；
mDrawerLayout=（抽屉布局）findViewById（R.id.抽屉布局）；
mDrawerList=（ListView）findViewById（R.id.list\u slidermenu）；
navDrawerItems=新的ArrayList（）；
//将导航抽屉项添加到阵列
//因弗多克
添加（新的NavDrawerItem（navMenuTitles[0]，navMenuIcons.getResourceId（0，-1））；
//进口港
添加（新的NavDrawerItem（navMenuTitles[1]，navMenuIcons.getResourceId（1，-1））；
//历史
添加（新的NavDrawerItem（navMenuTitles[2]，navMenuIcons.getResourceId（2，-1），true，“22”）；
//回收类型化数组
navMenuIcons.recycle（）；
setOnItemClickListener（新的SlideMenuClickListener（））；
//设置导航抽屉列表适配器
适配器=新的NavDroperListAdapter（getApplicationContext（），
纳维特姆斯）；
mDrawerList.setAdapter（适配器）；
//启用操作栏应用程序图标并将其作为切换按钮
getActionBar（）.setDisplayHomeAsUpEnabled（true）；
getActionBar（）.setHomeButtonEnabled（true）；
mDrawerToggle=新操作BarDrawerToggle（此，mDrawerLayout，
R.drawable.ic_抽屉，//导航菜单切换图标
R.string.app_name，//导航抽屉打开-可访问性说明
R.string.app_name//nav抽屉关闭-可访问性说明
) {
公共无效onDrawerClosed（视图）{
getActionBar（）.setTitle（mTitle）；
//调用onPrepareOptions菜单（）以显示操作栏图标
无效操作菜单（）；
}
打开图纸上的公共空白（视图抽屉视图）{
getActionBar（）.setTitle（mDrawerTitle）；
//调用onPrepareOptions菜单（）隐藏操作栏图标
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Framelayout to display Fragments -->
    <FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <!-- Listview to display slider menu -->
    <ListView
        android:id="@+id/list_slidermenu"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:divider="@color/list_divider"
        android:dividerHeight="1dp"        
        android:listSelector="@drawable/list_selector"
        android:background="@color/list_background"/>
</android.support.v4.widget.DrawerLayout>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <ListView
        android:id="@+id/docListView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</FrameLayout>

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    populateListView();
    return inflater.inflate(R.layout.fragment_document_item, container, false);
}