Cannot find database list pressing back button in blackberry - blackberry

Question

In screen1 i have 2 buttons a and b.i have given field change listener for both such that each pushes corresponding screen .When i press button 'a' it pushes say screen2 where i have used a keywordFilter to search words from sqlite database and is listed.These all are perfect when i run the application ,but when i press the back(or previous key) and then press the button 'a' from screen1 again i dont find any results from database.same thing happens to button b also .What cud b the pblm pls help.
Thank u so much in advance
Below is the class called after button 'a' is clicked
import net.rim.device.api.ui.*;
import net.rim.device.api.io.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.system.*;
import java.util.*;
import net.rim.device.api.database.Database;
import net.rim.device.api.database.DatabaseFactory;
import net.rim.device.api.database.Row;
import net.rim.device.api.database.Statement;
public final class KeywordFilter
{
private KeywordFilterField _keywordFilterField;
private WordList _wordList;
private Vector _words;
public KeywordFilter()
{
_words = getDataFromDatabase();
if(_words != null)
{
_wordList = new WordList(_words);
_keywordFilterField = new KeywordFilterField();
_keywordFilterField.setSourceList(_wordList, _wordList);
CustomKeywordField customSearchField = new CustomKeywordField();
_keywordFilterField.setKeywordField(customSearchField);
KeywordFilterScreen screen = new KeywordFilterScreen(this);
screen.setTitle(_keywordFilterField.getKeywordField());
screen.add(_keywordFilterField);
UiApplication ui = UiApplication.getUiApplication();
ui.pushScreen(screen);
}
else
{
UiApplication.getUiApplication().invokeLater(new Runnable()
{
public void run()
{
Dialog.alert("Error reading data file.");
System.exit(0);
}
});
}
}
KeywordFilterField getKeywordFilterField()
{
return _keywordFilterField;
}
private Vector getDataFromDatabase()
{
Vector words = new Vector();
Database d;
for(;;)
{
try
{
URI myURI=URI.create("file:///SDCard/Databases/MyTestDatabase.db");
d=DatabaseFactory.open(myURI);
Statement st=d.createStatement("SELECT eng,mal FROM Malayalam m,English e where e.Ecode=m.Mcode");
st.prepare();
net.rim.device.api.database.Cursor c=st.getCursor();
Row r;
while(c.next())
{
r=c.getRow();
String w=r.getString(0);
String meaning=r.getString(1);
words.addElement(new Word(w,meaning));
}}
catch ( Exception e )
{
System.out.println( e.getMessage() );
e.printStackTrace();
}
return words;
}
}
void addElementToList(Word w)
{
_wordList.addElement(w);
_keywordFilterField.updateList();
}
final static class CustomKeywordField extends BasicEditField
{
CustomKeywordField()
{
super(USE_ALL_WIDTH|NON_FOCUSABLE|NO_LEARNING|NO_NEWLINE);
setLabel("Search: ");
}
protected boolean keyChar(char ch, int status, int time)
{
switch(ch)
{
case Characters.ESCAPE:
if(super.getTextLength() > 0)
{
setText("");
return true;
}
}
return super.keyChar(ch, status, time);
}
protected void paint(Graphics graphics)
{
super.paint(graphics);
getFocusRect(new XYRect());
drawFocus(graphics, true);
}
}
}
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.system.*;
final class KeywordFilterScreen extends MainScreen
{
private KeywordFilter _app;
private KeywordFilterField _keywordFilterField;
public KeywordFilterScreen(KeywordFilter app)
{
_app = app;
_keywordFilterField = _app.getKeywordFilterField();
}
protected boolean keyChar(char key, int status, int time)
{
if (key == Characters.ENTER)
{
displayInfoScreen();
return true;
}
return super.keyChar(key, status, time);
}
public boolean invokeAction(int action)
{
switch(action)
{
case ACTION_INVOKE:
displayInfoScreen();
return true;
}
return super.invokeAction(action);
}
private void displayInfoScreen()
{
Word w = (Word)_keywordFilterField.getSelectedElement();
if(w != null)
{
InfoScreen infoScreen = new InfoScreen(w);
UiApplication ui = UiApplication.getUiApplication();
ui.pushScreen(infoScreen);
ui.popScreen(this);
}
}
private final static class InfoScreen extends MainScreen
{
InfoScreen(Word w)
{
setTitle(w.toString());
BasicEditField popField = new BasicEditField(":",w.getMeaning(),20,Field.NON_FOCUSABLE);
add(popField);
}
}
}
public class Word
{
private String _word;
private String _meaning;
public Word(String word, String meaning)
{
_word = word;
_meaning = meaning;
}
String getMeaning()
{
return _meaning;
}
public String toString()
{
return _word;
}
}
import net.rim.device.api.ui.component .*;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.util.*;
import java.util.*;
public class WordList extends SortedReadableList implements KeywordProvider
{
public WordList(Vector words)
{
super(new WordListComparator());
loadFrom(words.elements());
}
void addElement(Object element)
{
doAdd(element);
}
public String[] getKeywords( Object element )
{
if(element instanceof Word )
{
return StringUtilities.stringToWords(element.toString());
}
return null;
}
final static class WordListComparator implements Comparator
{
public int compare(Object o1, Object o2)
{
if (o1 == null || o2 == null)
throw new IllegalArgumentException("Cannot compare null words");
return o1.toString().compareTo(o2.toString());
}
}
}

Answer 1

add st.close(); and d.close() after accessing db in private Vector getDataFromDatabase() method just before closing the try block