Question

I feel like i am missing something simple and stupid. I have a list view with a few buttons at the top. The list view is initially populated with data. When you click a button the list view is supposed to populate its self based on a changed variable in the Where statement. In reality i could probably just start a new List activity but i feel like there is a better way.

I have been reading up on CursorAdapter.changeAdapter() and notifydatasetchanged() I have not implemented this yet because i am having a more basic problem.

I can successfully query the database and display the static results in the list. When i try to break process into steps i am running into an ERROR: Invalid statement in fillWindow. The best i understand this is caused by improperly closing cursors databases and DB helpers and for this reason people use content providers.

For now i am just trying to get this to work.

    public class DListView extends ListActivity implements OnClickListener{

public static final String NAME = "Name";

public static final String DESCRIPT = "Description";

public static final String DATABASE_TABLE = "Table";


public static final String DAY = "Day_id";

    /** Called when the activity is first created. */
private Cursor c = null;    

private String[] colsfrom = {"_id", NAME, DESCRIPT, DAY};
private int[] to = new int[] {R.id.text01, R.id.text02, R.id.text03, R.id.text04};

public int b = 0;

public int d = 0; 

   @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.drinklistview);

        View left = findViewById(R.id.left_button);
        left.setOnClickListener(this);
        View right = findViewById(R.id.right_button);
        right.setOnClickListener(this);

        Intent thisIntent = getIntent();
        b = thisIntent.getIntExtra("_b", 0); 
        //0 is the default argument is nothing is passed.
        d = thisIntent.getIntExtra("_d", 0); //same idea as above.

            c = fillList(); 

            /*this creates a new cursor adapter
            @param Context is the list context that you will be filling. 
            @param int layout is the layout that you will use for the rows
            @param Cursor is the cursor that was returned from the query
            @param from is the column names
            @param to is the layout ids that the fields will be put in. 
            @param from is the column names to map from
            @param to is the layout ids that the column fields will be put in. 
            */
            SimpleCursorAdapter myAdapter = new SimpleCursorAdapter(this, R.layout.row, c, colsfrom, to);
            setListAdapter(myAdapter);
   }

private Cursor fillList() {
    DBHelper DbHelper = new DBHelper(this);
    Cursor cursor;
    String wHERE = "_id = " + b + " AND Day_id = " + d ; 

    try {
        myDbHelper.openDataBase();  
    }
    catch(SQLException sqle){
        throw sqle; 
    }

    cursor = myDbHelper.getDrinks(DATABASE_TABLE, colsfrom, wHERE, null, null,null, null);

    myDbHelper.close();

    return cursor;

}

When i put the contents of fillList() in the onCreate() it displays data just fine. When i pull it out it gives me the ERROR. Why is this happening? If anyone has a better way of going about this i would love to read it. Or we can play a game called “What stupid thing am i doing wrong Now?
Thankyou.

EDIT:From DBHelper

public void openDataBase() throws SQLException{

    //Open the database
    String myPath = DB_PATH + DB_NAME;
    myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}

    @Override
    public synchronized void close() {

        if(myDataBase != null)
            myDataBase.close();
        super.close();
    }

I am thinking that my problem line is the super.close() I believe that this line closes the database and anything affiliated with it which means the cursor that i try to use after its closed. I may be wrong though. Please explain if you can.

Answer 1

Your problem is right here, in your fillList():

myDbHelper.close(); // <--- here
return cursor;

you make a cursor object but close your database connection before you even get to use it (this component of the database) which would render it useless or null if you would. Usually you close the cursor and then the database. But that’s not throwing the error. That error specifically is because you hooked up this cursor to a cursorAdapter trying to fill your listView with nothing. Move that and it should be gone.

So where do you move it then? If you have a cursor hooked up to listView, it needs to be open the entire time, otherwise you’ll get another error saying “attempting to re-open an already closed object”. I’d suggest putting in the onDestroy() when then listView is being chucked as well.