Question

I’ve been beating my head around trying to populate a ListView with data from an SQLite database and can’t seem to figure it out. I’ve read countless tutorials and equally countless posts here, but I’m obviously not getting something critical. Was hoping someone could give me a hint as to why the following two pieces of code aren’t working together, or if I should be looking at something else entirely. Any help would be appreciated. The result I’m getting is a force close.

Method that initiates populating ListView object

public void displayNurseRoster(){

    listView = (ListView) findViewById(R.id.list);

    // create instance of DbCommunicator
    DbCommunicator rosterView = new DbCommunicator(this);

    // open instance
    rosterView.open();

    // instantiate SimpleCursorAdapter instance and set value
    SimpleCursorAdapter cursorAdapter;
    cursorAdapter = rosterView.getRosterListViewAdapter(this);

    // close database instance
    rosterView.close();

    // set adapter to listView
    listView.setAdapter(cursorAdapter);
}

Method that returns SimpleCursorAdapter:

public SimpleCursorAdapter getRosterListViewAdapter (Context context) {

    // method variables 
    int[] to = new int[] {R.id.rosterListLname};
    // used ArrayList because of unpredictability of array length
    List<String> dataArray = new ArrayList<String>(); 
    String[] columns = new String[] {KEY_NURSE_ROWID, KEY_LNAME}; 

    // create cursor
    Cursor cursor = sqldb.query(NURSE_TABLE, columns, null, null, null,
            null, KEY_LNAME);

    int iLname = cursor.getColumnIndex(KEY_LNAME);

    cursor.moveToFirst();

    String result = "";

    while(!cursor.isAfterLast()){
        result = result 
                + cursor.getString(iLname) + "\n";
        dataArray.add(result);

    }
    // convert ArrayList to String array for use with SimpleCursorAdapter
    String [] from = (String[]) dataArray.toArray();

    SimpleCursorAdapter adapter = new SimpleCursorAdapter(context,
            R.layout.edit_roster, cursor, from, to);

    return adapter;
}

Answer 1

Okay, I got it to work and wanted to share to help out anyone else struggling with this and 2) to get feedback on my fix in case anyone with more experience has a better suggestion.

I actually wanted to show three items in the list view, so here’s the code that worked. One of the problems I was having was that I was extending ListActivity, but found in another StackOverflow post that that is not a good idea when there is only one list view to worry about.

package com.deadEddie.staffingmanagement;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

public class EditRoster extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.edit_roster);
    displayNurseRoster();   
}

public void displayNurseRoster(){

    ListView listView = (ListView) findViewById(R.id.list);

    int[] to = new int[] {
            R.id.rosterListLname, 
            R.id.rosterListFname, 
            R.id.rosterListMI };

    String[] from = new String [] {
            DbCommunicator.KEY_LNAME, 
            DbCommunicator.KEY_FNAME, 
            DbCommunicator.KEY_MI};

    // create instance of DbCommunicator
    DbCommunicator rosterView = new DbCommunicator(this);

    // open instance
    rosterView.open();

    // get & manage cursor
    Cursor cursor = rosterView.getRosterCursor(this);
    startManagingCursor(cursor);

    // instantiate cursor adaptor
    ListAdapter adapter = new SimpleCursorAdapter(this,
            R.layout.nurse_list, cursor, from, to);
    cursor.moveToNext();

    // set adapter to listView
    listView.setAdapter(adapter);
}// displayNurseRoster()
}

Here’s the method in my DbCommunicator class. What finally made the difference was that I was not creating an instance of SQLiteQueryBuilder and using that, but instead I was using sqldb.query(…), as shown above. I’m not sure what the difference is, but it finally did the trick. If anyone would like to share, please do.

public Cursor getRosterCursor (Context context) {

    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
    queryBuilder.setTables(NURSE_TABLE);

    Cursor cursor = queryBuilder.query(sqldb, new String[] {
            KEY_NURSE_ROWID, 
            KEY_LNAME,
            KEY_FNAME,
            KEY_MI},
            null, null, null, null, null);

    return cursor;
}

A couple other newbie lessons for anyone else out there:
1. Always use the “_id” field in the cursor. The cursor cannot function without that.
2. The while or for loop is not necessary for a simple list view. The cursor adapter handles that.
3. There is no need to call the moveToFirst() method on the cursor.

Hope that’s helpful to someone.