Android Listview将填充，但适配器声明为空

所以我在夏天开发了一个应用程序。它将项目存储在数据库中，在listview中显示它们（否则会使Toast告诉用户其为空），并允许用户通过单击一个项目来查看详细信息。最终，我计划让搜索条件缩小列表的范围，但我还没有做到

我的问题是listview似乎正在填充，但应用程序会制作Toast

ResultsActivity.java

public class ResultsActivity extends FragmentActivity implements ResultsFragment.OnPlantSelectedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_results);
    }// method: FragmentActivity.onCreate() 

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.results, menu);
        return true;
    }// method: FragmentActivity.onCreateOptionsMenu()

    /* Custom methods */

    //@Override
    public void onPlantSelected(long id){
        Intent intent = new Intent(this, PlantViewActivity.class);
        //TODO confirm id
        intent.putExtra(DBContentProvider.KEY_PLANT_ID, id);
        startActivity(intent);      
    }// method: ResultsFragment.OnPlantSelectedListener.onPlantSelected(long)
}// class: ResultsActivity extends ListActivity

ResultsFragment.java

public class ResultsFragment extends ListFragment implements LoaderManager.LoaderCallbacks<Cursor>{
    private static OnPlantSelectedListener emptyPlantSelectedListener = new OnPlantSelectedListener(){
        @Override
        public void onPlantSelected(long id){}
    };
    private static OnPlantSelectedListener plantSelectedListener = emptyPlantSelectedListener;

    private static final String STATE_ACTIVATED_POSITION = "activated_position";
    private int activatedPosition = ListView.INVALID_POSITION;
    private SimpleCursorAdapter adapter;

    public ResultsFragment(){}

    /* Fragment Lifespan */
    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        String[] dbPlantColumns = {DBContentProvider.KEY_GENUS_TEXT, DBContentProvider.KEY_SPECIES, 
                DBContentProvider.KEY_COMMON_NAME_GROUP};
        int[] fragPlantFields = {R.id.result_item_txt_genus, R.id.result_item_txt_species, 
                R.id.result_item_txt_common_name};
        getLoaderManager().initLoader(0x01, null, this);//null can be replaced by a Bundle of search criteria
        adapter = new SimpleCursorAdapter(getActivity().getApplicationContext(), R.layout.list_item_results, 
                null, dbPlantColumns, fragPlantFields, CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
        setListAdapter(adapter);
        if(adapter.isEmpty())//This returns true
            Toast.makeText(getActivity().getApplicationContext(), "Nothing returned from the database", 
                    Toast.LENGTH_LONG).show();
    }// method: Activity.onCreate(Bundle)

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState){
        super.onViewCreated(view, savedInstanceState);
        if (savedInstanceState != null && savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)){
            setActivatedPosition(savedInstanceState.getInt(STATE_ACTIVATED_POSITION));
        }
    }// method: ListFragment.onViewCreated(View, Bundle)

    @Override
    public void onAttach(Activity activity){
        super.onAttach(activity);
        if (!(activity instanceof OnPlantSelectedListener)){
            throw new IllegalStateException("Activity must implement fragment's listener.");
        }
        plantSelectedListener = (OnPlantSelectedListener) activity;
    }// method: ListFragment.onAttach(Activity)

    @Override
    public void onDetach(){
        super.onDetach();
        plantSelectedListener = emptyPlantSelectedListener;
    }// method: ListFragment.onDetach()

    @Override
    public void onSaveInstanceState(Bundle outState){
        super.onSaveInstanceState(outState);
        if (activatedPosition != ListView.INVALID_POSITION){
            outState.putInt(STATE_ACTIVATED_POSITION, activatedPosition);
        }
    }// method: ListFragment.onSaveInstanceState(Bundle)

    /* LoaderManager abstract methods */    
    @Override
    public Loader<Cursor> onCreateLoader(int id, Bundle args){
        //TODO parse args for searching. Second null is String[]; index 0-17 are search arguments.
        String[] arguments = new String[18];
        String[] dbPlantColumns = {DBContentProvider.TABLE_PLANT + "." + DBContentProvider.KEY_PLANT_ID, 
                DBContentProvider.KEY_FAMILY_TEXT, DBContentProvider.KEY_GENUS_TEXT, DBContentProvider.KEY_SPECIES, 
                DBContentProvider.KEY_COMMON_NAME_GROUP, DBContentProvider.KEY_GROWTH_FORM_TEXT};
        CursorLoader cursorLoader = new CursorLoader(getActivity(), Uri.parse(DBContentProvider.CONTENT_URI_STRING + 
                "search"), dbPlantColumns, null, arguments, null);
        return cursorLoader;
    }// method: LoaderCallbacks.onCreateLoader(int, Bundle)

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor cursor){
        adapter.swapCursor(cursor);
    }// method: LoaderCallbacks.onLoadFinished(Loader<Cursor>, Cursor)

    @Override
    public void onLoaderReset(Loader<Cursor> loader){
        adapter.swapCursor(null);
    }// method: LoaderCallbacks.onLoaderReset(Loader<Cursor>)

    /* ListFragment response methods */
    @Override
    public void onListItemClick(ListView listView, View view, int position, long id){
        super.onListItemClick(listView, view, position, id);

        plantSelectedListener.onPlantSelected(id /*Get id of plant at this position*/);
    }// method: ListFragment.onListItemClick(Listview, View, int, long)

    public void setActivateOnItemClick(boolean activateOnItemClick){
        getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
    }// method: setActivateOnItemClick(boolean)

    private void setActivatedPosition(int position){
        if(position == ListView.INVALID_POSITION){
            getListView().setItemChecked(activatedPosition, false);
        } 
        else{
            getListView().setItemChecked(position, true);
        }
        activatedPosition = position;
    }//method: setActiviatedPosition(int)

    /**
     * OnPlantSelectedListener is used by the fragment and the activity to 
     * make sure that the selection of a plant is dealt with correctly.
     */
    public interface OnPlantSelectedListener{
        public void onPlantSelected(long id);
    }// interface: OnPlantSelectedListener
}// class: ResultsFragment extends ListFragment

公共类ResultsFragment扩展ListFragment实现LoaderManager.LoaderCallbacks{
私有静态OnPlantSelectedListener emptyPlantSelectedListener=新建OnPlantSelectedListener（）{
@凌驾
已选定的公用无效（长id）{}
};
私有静态OnPlantSelectedListener plantSelectedListener=emptyPlantSelectedListener；
私有静态最终字符串状态\u ACTIVATED\u POSITION=“ACTIVATED\u POSITION”；
private int activatedPosition=ListView.INVALID_POSITION；
专用SimpleCursorAdapter适配器；
public ResultsFragment（）{}
/*碎片寿命*/
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
String[]dbPlantColumns={DBContentProvider.KEY\u generis\u TEXT，DBContentProvider.KEY\u SPECIES，
DBContentProvider.KEY\u COMMON\u NAME\u GROUP}；
int[]fragPlantFields={R.id.result\u item\u txt\u属，R.id.result\u item\u txt\u种，
R.id.result\u item\u txt\u common\u name}；
getLoaderManager（）.initLoader（0x01，null，this）；//null可以由一组搜索条件替换
adapter=new SimpleCursorAdapter（getActivity（）.getApplicationContext（），R.layout.list\u item\u结果，
null、dbPlantColumns、fragPlantFields、CursorAdapter.FLAG\u REGISTER\u CONTENT\u OBSERVER）；
setListAdapter（适配器）；
if（adapter.isEmpty（））//返回true
Toast.makeText（getActivity（）.getApplicationContext（），“数据库未返回任何内容”，
Toast.LENGTH_LONG）.show（）；
}//方法：Activity.onCreate（Bundle）
@凌驾
已创建视图上的公共void（视图，捆绑保存状态）{
super.onViewCreated（视图，savedInstanceState）；
if（savedInstanceState！=null&&savedInstanceState.containsKey（状态激活位置））{
setActivatedPosition（savedInstanceState.getInt（STATE_ACTIVATED_POSITION））；
}
}//方法：ListFragment.onViewCreated（视图，捆绑）
@凌驾
公共事务主任（活动）{
超级转速计（活动）；
if（！（PlantSelectedListener上的活动实例））{
抛出新的IllegalStateException（“活动必须实现片段的侦听器”）；
}
plantSelectedListener=（OnPlantSelectedListener）活动；
}//方法：ListFragment.onAttach（活动）
@凌驾
公共无效连接（）{
super.onDetach（）；
plantSelectedListener=emptyPlantSelectedListener；
}//方法：ListFragment.onDetach（）
@凌驾
SaveInstanceState上的公共无效（束超出状态）{
super.onSaveInstanceState（超出状态）；
if（activatedPosition！=列表视图。位置无效）{
outState.putInt（状态激活位置，激活位置）；
}
}//方法：ListFragment.onSaveInstanceState（Bundle）
/*LoaderManager抽象方法*/
@凌驾
公共加载器onCreateLoader（int-id，Bundle-args）{
//TODO解析用于搜索的参数。第二个null是字符串[]；索引0-17是搜索参数。
字符串[]参数=新字符串[18]；
字符串[]dbPlantColumns={DBContentProvider.TABLE_PLANT+““+DBContentProvider.KEY_PLANT_ID，
DBContentProvider.KEY_族_文本，DBContentProvider.KEY_属_文本，DBContentProvider.KEY_物种，
DBContentProvider.KEY\u COMMON\u NAME\u GROUP，DBContentProvider.KEY\u GROWTH\u FORM\u TEXT}；
CursorLoader CursorLoader=新的CursorLoader（getActivity（），Uri.parse（DBContentProvider.CONTENT\u Uri\u STRING+
“搜索”），dbPlantColumns，null，arguments，null）；
返回游标装入器；
}//方法：LoaderCallbacks.onCreateLoader（int，Bundle）
@凌驾
public void onLoadFinished（加载器，光标）{
适配器.swapCursor（游标）；
}//方法：LoaderCallbacks.onLoadFinished（加载器，光标）
@凌驾
公共void onLoaderReset（加载器）{
适配器.swapCursor（空）；
}//方法：LoaderCallbacks.onLoaderReset（Loader）
/*列表片段响应方法*/
@凌驾
public void onListItemClick（ListView ListView、视图视图、int位置、长id）{
super.onListItemClick（列表视图、视图、位置、id）；
plantSelectedListener.onPlantSelected（id/*获取此位置的植物id*/）；
}//方法：ListFragment.onListItemClick（Listview、View、int、long）
public void setActivateOnItemClick（布尔activateOnItemClick）{
getListView（）.setChoiceMode（ListView.CHOICE\u MODE\u SINGLE）；
}//方法：setActivateOnItemClick（布尔值）
私有void setActivatedPosition（内部位置）{
if（position==ListView.INVALID_position）{
getListView（）.setItemChecked（activatedPosition，false）；
} 
否则{
getListView（）.setItemChecked（位置，true）；
}
激活位置=位置；
}//方法：setActivatedPosition（int）
/**
*片段和活动使用OnPlantSelectedListener来
*确保正确处理植物的选择。
*/
PlantSelectedListener上的公共接口{
已选定的公用id（长id）；
}//接口：OnPlantSelectedListener
}//类：ResultsFragment扩展ListFragment

activity_results.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".ResultsActivity"
    android:id="@+id/Results_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- @android:id/list is the necessary id for the activity to find it. -->
    <ListView 
        android:id="@android:id/list" 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="5dp">
    </ListView>
    <TextView
        android:id="@+id/results_empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/txt_no_results"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:name="edu.dordt.grassrootsplantid.ResultsFragment"
    android:id="@+id/Result_Fragment"/>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/Result_Item_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp">

    <TextView
        android:id="@+id/result_item_txt_lbl_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_common_name"/>

    <TextView 
        android:id="@+id/result_item_txt_lbl_scientific_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:text="@string/lbl_scientific_name"/>
    <TextView
        android:id="@+id/result_item_txt_genus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_scientific_name"
        android:layout_below="@id/result_item_txt_lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_species"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_genus"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:layout_marginLeft="5dp"/>
</RelativeLayout>

fragment_results.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".ResultsActivity"
    android:id="@+id/Results_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- @android:id/list is the necessary id for the activity to find it. -->
    <ListView 
        android:id="@android:id/list" 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="5dp">
    </ListView>
    <TextView
        android:id="@+id/results_empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/txt_no_results"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:name="edu.dordt.grassrootsplantid.ResultsFragment"
    android:id="@+id/Result_Fragment"/>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/Result_Item_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp">

    <TextView
        android:id="@+id/result_item_txt_lbl_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_common_name"/>

    <TextView 
        android:id="@+id/result_item_txt_lbl_scientific_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:text="@string/lbl_scientific_name"/>
    <TextView
        android:id="@+id/result_item_txt_genus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_scientific_name"
        android:layout_below="@id/result_item_txt_lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_species"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_genus"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:layout_marginLeft="5dp"/>
</RelativeLayout>

list_item_results.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".ResultsActivity"
    android:id="@+id/Results_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- @android:id/list is the necessary id for the activity to find it. -->
    <ListView 
        android:id="@android:id/list" 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="5dp">
    </ListView>
    <TextView
        android:id="@+id/results_empty"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/txt_no_results"/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:name="edu.dordt.grassrootsplantid.ResultsFragment"
    android:id="@+id/Result_Fragment"/>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/Result_Item_Lin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="5dp">

    <TextView
        android:id="@+id/result_item_txt_lbl_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_common_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_common_name"/>

    <TextView 
        android:id="@+id/result_item_txt_lbl_scientific_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:text="@string/lbl_scientific_name"/>
    <TextView
        android:id="@+id/result_item_txt_genus"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_lbl_scientific_name"
        android:layout_below="@id/result_item_txt_lbl_common_name"/>
    <TextView
        android:id="@+id/result_item_txt_species"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_toRightOf="@id/result_item_txt_genus"
        android:layout_below="@id/result_item_txt_lbl_common_name"
        android:layout_marginLeft="5dp"/>
</RelativeLayout>

我可能误解了