所以我在夏天开发应用程序。它将项目存储在数据库中，在列表视图中显示它们（否则使Toast告诉用户它为空），并允许用户通过单击查看详细信息来查看详细信息。最终我计划让搜索条件缩小到列表范围，但我还没有。
我的问题是列表视图似乎正在填充，但该应用程序使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
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>
fragment_results.xml
<?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"/>
list_item_results.xml
<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>
我可能误解了如何使用片段，但是为了使用我使用内容提供者所遵循的教程，这是必要的。我没有在这里放入内容提供商，但我很确定它正在工作（好吧......在别的地方打破了，但我想我可以处理那个）。如果有人想看到它，我可以编辑我的问题。
如果它完全相关，则列表项具有其数据并且是可点击的，但它们看起来是灰色的，就像它们不可点击一样。也许这是一个造型问题，但我认为他们会使用应用程序其余部分共享的风格。
但重申我的问题，列表视图正在填充，但适配器声称是空的。我不确定它将会是一个多大的问题，但我想要一种让他们同意的方法，或者解释为什么他们可能不需要这样做。
答案 0 :(得分：0)
或解释为什么他们可能不需要。
他们似乎不同意，因为在调用isEmpty时适配器确实是空的。 Android的Loaders在一个单独的线程上进行工作（异步）。
我建议setting empty view而不是使用吐司。