我遇到了这个问题，当我更改设备的方向时，由于某种原因，与我的 ListFragment 关联的 ListView 的屏幕表示被保留，并且新的 ListView 在其下方膨胀。为了给你一些背景信息，我正在创建一个非常简单的应用程序，其目的是测试我创建的一些 DAO 对象。我更愿意发布一些截图来描述我的应用程序正在经历的行为，但不幸的是，我目前的声誉太低了。
我能描述的最好的情况是，当我将设备的方向从纵向更改为横向（反之亦然）时，它会膨胀一个全新的 ListView 而不会缩小前一个。我已经研究了几天了，老实说，我很难过。你们可以提供的任何帮助将不胜感激。
这是 ListFragment 的代码：
package edu.uark.csce.mobile.healthyshopper;
import android.app.ListFragment;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.CursorLoader;
import android.content.Loader;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
/**
* A fragment representing a list of Items.
* <p />
* <p />
* Activities containing this fragment MUST implement the {@link Callbacks}
* interface.
*/
public class ViewFragment extends ListFragment implements
LoaderCallbacks<Cursor> {
// Class Fields:
private static final String TAG = "healthyshopper.ViewFragment";
private static final int MAIN_DB_LOADER = 0;
// In the final application, any query to the main database needs to return
// at least these fields:
private final String[] NECESSARY_COLUMNS = { DAOContentProvider.FOOD_DES,
DAOContentProvider.FOOD_CALORIES, DAOContentProvider.FOOD_FAT,
DAOContentProvider.FOOD_CARBS, DAOContentProvider.FOOD_PROTEIN };
private final String FROM[] = {DAOContentProvider.FOOD_GROUP, DAOContentProvider.FOOD_DES,
DAOContentProvider.FOOD_MANUFAC, DAOContentProvider.FOOD_PROTEIN,
DAOContentProvider.FOOD_FAT, DAOContentProvider.FOOD_CARBS,
DAOContentProvider.FOOD_CALORIES, DAOContentProvider.FOOD_SERV_SIZE};
private final int TO[] = {R.id.fd_group, R.id.shrt_desc,
R.id.manufac, R.id.protein,
R.id.fat, R.id.carb,
R.id.cal, R.id.amt};
private int threadMode;
private int queryType;
private int foodGroupId;
private CursorLoader loader;
private SimpleCursorAdapter listAdapter;
// Preference Option Constants:
private int UI_THREAD = 0;
private int BRANCHED_THREAD = 1;
private int ALL_ROWS = 0;
private int SPECIFIC_FD_GROUP = 1;
private int LIMITED_ROWS = 2;
private OnFragmentInteractionListener mListener;
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public ViewFragment() {
}
/***************************************
* Life cycle callbacks:
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.e(TAG, "in onCreate()");
setRetainInstance(true);
}
@Override
public void onActivityCreated(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
if(savedInstanceState == null){
listAdapter = new SimpleCursorAdapter(getActivity(), R.layout.list_node, null, FROM, TO, 0);
setListAdapter(listAdapter);
}
}
@Override
public void onStart(){
super.onStart();
}
@Override
public void onResume(){
super.onResume();
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(getActivity()
.getApplicationContext());
Log.d(TAG, preferences.getString("THREADING_MODE", "BLANK"));
//Load testing preferences:
threadMode = Integer.valueOf(preferences.getString("THREADING_MODE","0"));
queryType = Integer.valueOf(preferences.getString("QUERY_TYPE", "0"));
foodGroupId = Integer.valueOf(preferences.getString("FOOD_GROUP", "0")); // Default
if (threadMode == BRANCHED_THREAD) {
loader = (CursorLoader) getLoaderManager().initLoader(
MAIN_DB_LOADER, null, this);
} else {
String[] projection = null;
String selection = null;
if (queryType == SPECIFIC_FD_GROUP) {
Log.d(TAG, "Query Type: " + (getResources().getStringArray(R.array.query_type_select))[queryType]);
selection = DAOContentProvider.FOOD_GROUP + " = " + foodGroupId;
} else if (queryType == LIMITED_ROWS) {
projection = NECESSARY_COLUMNS;
}
/*This is for testing only. Ordinarily, you should NEVER perform Db operations on the UI thread.*/
listAdapter.swapCursor(getActivity().getContentResolver().query(
DAOContentProvider.CONTENT_URI, projection, selection, null, null));
}
}
@Override
public void onPause(){
super.onPause();
}
@Override
public void onStop(){
super.onStop();
}
@Override
public void onDestroyView(){
super.onDestroyView();
Log.e(TAG, "in onDestroyView()");
setListAdapter(null);
listAdapter.swapCursor(null);
listAdapter = null;
}
@Override
public void onDestroy(){
super.onDestroy();
}
@Override
public void onDetach(){
super.onDetach();
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
if (null != mListener) {
}
}
/**
* 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(String id);
}
/**
* LoaderManager Callbacks;
*/
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
switch (id) {
case MAIN_DB_LOADER:
String[] projection = null;
String selection = null;
if (queryType == SPECIFIC_FD_GROUP) {
Log.d(TAG,
"Query Type: "
+ (getResources()
.getStringArray(R.array.query_type_select))[queryType]);
selection = DAOContentProvider.FOOD_GROUP + " = " + foodGroupId;
} else if (queryType == LIMITED_ROWS) {
projection = NECESSARY_COLUMNS;
}
return new CursorLoader(getActivity(),
DAOContentProvider.CONTENT_URI, projection, selection,
null, null);
default:
return null;
}
}
@Override
public void onLoadFinished(Loader<Cursor> arg0, Cursor arg1) {
listAdapter.swapCursor(arg1);
listAdapter.notifyDataSetChanged();
}
@Override
public void onLoaderReset(Loader<Cursor> arg0) {
listAdapter.swapCursor(null);
listAdapter.notifyDataSetChanged();
}
}
这是其相关活动的代码：
package edu.uark.csce.mobile.healthyshopper;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
public class TestingActivity extends Activity implements ViewFragment.OnFragmentInteractionListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_testing);
ViewFragment list = new ViewFragment();
getFragmentManager().beginTransaction().add(R.id.test_layout, list).commit();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.testing, menu);
return true;
}
@Override
public void onFragmentInteraction(String id) {
// TODO Auto-generated method stub
}
}