The application crashes when the screen turns.

When you rotate the phone while in MainActivity, the application crashes and issues such an event.

MainActivity

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener, LoaderManager.LoaderCallbacks<Cursor> { ExpandableListView expList; DBHeler db; ExpListAdapter adapter; final private static int LOADER = 1; private int currentLoader; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); db = new DBHeler(this); String[] groupFrom = { Contract.Entry.COLUMN_NAME }; int[] groupTo = { android.R.id.text1 }; String[] childFrom = { Contract.Entry.COLUMN_NAME }; int[] childTo = { android.R.id.text1 }; adapter = new ExpListAdapter( this, null, R.layout.item_group, // разметка корневых айтемов groupFrom, groupTo, R.layout.item, // разметка вложенных айтемов childFrom, childTo); expList = (ExpandableListView) findViewById(R.id.expList); expList.setGroupIndicator(null); expList.setAdapter(adapter); getSupportLoaderManager().initLoader(LOADER, null, this); } @Override protected void onResume() { super.onResume(); expList.setOnChildClickListener(new ExpandableListView.OnChildClickListener() { @Override public boolean onChildClick(ExpandableListView expandableListView, View view, int i, int i1, long l) { Intent intent = new Intent(MainActivity.this, Dish.class); long id = l; intent.putExtra("id", id); startActivity(intent); return true; } }); getSupportLoaderManager().restartLoader(currentLoader, null, this); } static class MyCursorLoader extends CursorLoader { DBHeler dbHeler; final int loaderID; public MyCursorLoader(Context context, DBHeler dbHeler, int id) { super(context); this.dbHeler = dbHeler; loaderID = id; } @Override protected Cursor onLoadInBackground() { return dbHeler.getCategory(); } } @Override public Loader<Cursor> onCreateLoader(int id, Bundle bundle) { return new MyCursorLoader(this, db, id); } @Override public void onLoadFinished(Loader<Cursor> loader, Cursor data) { adapter.changeCursor(data); } @Override public void onLoaderReset(Loader<Cursor> loader) { adapter.changeCursor(null); } } 

Code for DB

 public class DBHeler extends SQLiteOpenHelper { private static String DB_PATH; private static final String DATABASE_NAME = "dbase.db"; private static final int DATABASE_VERSION = 1; public SQLiteDatabase database; private Context myContext; public DBHeler(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); this.myContext = context; try { //получаем путь до БД вместе с именем. DB_PATH = myContext.getDatabasePath(DATABASE_NAME).toString(); createDataBase(); openDataBase(); } catch (IOException e) { e.printStackTrace(); } } public Cursor getSingleDost(long id) { return this.getReadableDatabase().query(Contract.Entry.TABLE_DOST, null, Contract.Entry._ID + " = " + id, null, null, null, null); } public Cursor getFavoritesDost() { return database.query(Contract.Entry.TABLE_DOST, null, Contract.Entry.COLUMN_FAVORITE + " = 1", null, null, null, null); } public Cursor getCategory() { return this.getReadableDatabase().query(Contract.Entry.TABLE_CATEGORY, null, null, null, null, null, null); } public Cursor getDost(long categoryID) { return this.getReadableDatabase().query(Contract.Entry.TABLE_DOST, null, Contract.Entry.COLUMN_CATEGORYID + " = " + categoryID, null, null, null, null); } public void createDataBase() throws IOException { boolean dbExist = checkDataBase(); if (!dbExist) { this.getReadableDatabase(); try { copyDataBase(); } catch (IOException e) { throw new Error("Error copying database"); } } } private boolean checkDataBase(){ SQLiteDatabase checkDB = null; try { checkDB = SQLiteDatabase.openDatabase(DB_PATH, null, SQLiteDatabase.OPEN_READONLY); } catch (SQLiteException e) { // база не существует } if (checkDB != null) { checkDB.close(); } return checkDB != null; } private void copyDataBase() throws IOException { InputStream myInput = myContext.getAssets().open(DATABASE_NAME); String outFileName = DB_PATH; OutputStream myOutput = new FileOutputStream(outFileName); byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } myOutput.flush(); myOutput.close(); myInput.close(); } public void openDataBase() throws SQLException { database = SQLiteDatabase.openDatabase(DB_PATH, null, SQLiteDatabase.OPEN_READWRITE); } @Override public synchronized void close() { if(database != null) database.close(); super.close(); } @Override public void onCreate(SQLiteDatabase db) { } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } } 

Mistake

 java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteQuery: SELECT * FROM category at android.database.sqlite.SQLiteClosable.acquireReference(SQLiteClosable.java:55) at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:58) at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:151) at android.database.sqlite.SQLiteCursor.onMove(SQLiteCursor.java:123) at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:236) at android.widget.CursorTreeAdapter$MyCursorHelper.moveTo(CursorTreeAdapter.java:446) at android.widget.CursorTreeAdapter.getGroupView(CursorTreeAdapter.java:196) at android.widget.ExpandableListConnector.getView(ExpandableListConnector.java:446) at android.widget.AbsListView.obtainView(AbsListView.java:2934) at android.widget.ListView.makeAndAddView(ListView.java:1945) at android.widget.ListView.fillDown(ListView.java:719) at android.widget.ListView.fillFromTop(ListView.java:785) at android.widget.ListView.layoutChildren(ListView.java:1721) at android.widget.AbsListView.onLayout(AbsListView.java:2728) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1080) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:131) at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42) at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1375) at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:870) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1193) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:344) at android.widget.FrameLayout.onLayout(FrameLayout.java:281) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1742) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:344) at android.widget.FrameLayout.onLayout(FrameLayout.java:281) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1742) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585) at android.widget.LinearLayout.onLayout(LinearLayout.java:1494) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:344) at android.widget.FrameLayout.onLayout(FrameLayout.java:281) at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:3129) at android.view.View.layout(View.java:17972) at android.view.ViewGroup.layout(ViewGroup.java:5814) at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2669) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2370) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1440) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7421) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:920) at android.view.Choreographer.doCallbacks(Choreographer.java:695) at android.view.Choreographer.doFrame(Choreographer.java:631) at android.view.Choreographer$FrameDisplayEventRec 

What could be the reason?