listview - Android cursor error - "make sure cursor is initialized correctly before accessing data from it..."

Question

I've got an activity where a viewflipper shows a list containing the artists from mediastore, which onitem click display a list of albums by the chosen artist, which in turn displays the songs on that album. Once a song is clicked, it should populate a textview with the string 'title'.

Until this point, all of the cursors are working fine, but the very last one seems to get put out of position somehow. Could anyone tell me why logcat is telling me:

05-07 23:58:54.195: E/AndroidRuntime(1961): java.lang.IllegalStateException: Couldn't read row 3, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

The particular row which cannot be read varies depending on which artist/album/song is chosen. The code is as follows. Thank you very much for your help.

package music.flipper;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.provider.BaseColumns;
import android.provider.MediaStore;
import android.provider.MediaStore.Audio.AlbumColumns;
import android.provider.MediaStore.Audio.ArtistColumns;
import android.provider.MediaStore.Audio.AudioColumns;
import android.provider.MediaStore.MediaColumns;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
import android.widget.ViewFlipper;

public class MusicFlipper extends Activity implements OnItemClickListener {
    /** Called when the activity is first created. */

    ViewFlipper viewflipper;
    Cursor cursor;

    private String currentList = "Artist";
    @SuppressWarnings("deprecation")
    @Override
    public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

        setContentView(R.layout.flipper);
        //set the main view to flipper.
        viewflipper = (ViewFlipper) findViewById(R.id.viewFlipper1);

        String[] columns = { 
                BaseColumns._ID,
                ArtistColumns.ARTIST 
                };
        //The columns to return for each row.   

        cursor = managedQuery(MediaStore.Audio.Artists.EXTERNAL_CONTENT_URI,
            columns, null, null, null);

        ListView listView = (ListView) findViewById(R.id.listView1);
        listView.setOnItemClickListener(this);

        //set an onitemclicklistener to the first listview in flipper

        String[] displayFields = new String[] { ArtistColumns.ARTIST };
        //set all the artist names to the array 'displayfields'
        int[] displayViews = new int[] { R.id.rowItem };
        //number of rows to display and where to bind them

        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
            R.layout.row_item, cursor, displayFields, displayViews);
        listView.setAdapter(adapter); }
        //Take the display fields array, and bind to the matching display row

     @SuppressWarnings("deprecation")

    public void onItemClick(AdapterView<?> a, View v, int position, long id) {

        if( currentList.equals("Artist")) {
            if (cursor.moveToPosition(position)) {
            //once an item is clicked, move the cursor to that items position

            String where = AudioColumns.ARTIST + "=?";
            // Have the cursor look within the artist row?

            String whereVal[] = { cursor.getString(cursor
          .getColumnIndex(AlbumColumns.ARTIST)) };
            //Choose the particular row with the chosen artist's name

            String[] columns = {
                    BaseColumns._ID,
                    AudioColumns.ALBUM,
               };

                String orderBy = BaseColumns._ID;

            cursor = managedQuery(MediaStore.Audio.Albums.EXTERNAL_CONTENT_URI,
                columns, where, whereVal, orderBy);

            ListView listView = (ListView) findViewById(R.id.listView2);
            listView.setOnItemClickListener(this);
            String[] displayFields = new String[] { AudioColumns.ALBUM };
            int[] displayViews = new int[] { R.id.rowItem };
            SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
                R.layout.row_item, cursor, displayFields, displayViews);
            listView.setAdapter(adapter);
            currentList = "Album";
            viewflipper.showNext();}

        } if (currentList.equals("Album")) {
            if (cursor.moveToPosition(position)) {

                String where = AudioColumns.ALBUM
                + "=?";

                String whereVal[] = { cursor.getString(cursor
                .getColumnIndex(AlbumColumns.ALBUM)) };

                String[] columns = {
                        MediaColumns.DATA,
                        BaseColumns._ID,
                        MediaColumns.TITLE,
                        MediaColumns.DISPLAY_NAME,
                        MediaColumns.MIME_TYPE,
                   };

                    String orderBy = MediaColumns.TITLE;

                cursor = managedQuery(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                    columns, where, whereVal, orderBy);

                ListView listView = (ListView) findViewById(R.id.listView3);
                listView.setOnItemClickListener(this);
                String[] displayFields = new String[] { MediaColumns.TITLE };
                int[] displayViews = new int[] { R.id.rowItem };
                SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
                    R.layout.row_item, cursor, displayFields, displayViews);
                listView.setAdapter(adapter);
                currentList.equals("Songs");
                viewflipper.showNext();}


        } if (currentList.equals("Songs")) {
            if (cursor.moveToPosition(position)) {

                String title = cursor.getString(cursor.getColumnIndex(MediaColumns.TITLE));

                TextView myTextView = (TextView) findViewById(R.id.title);
                myTextView.setText(title);

            }
        }
    }
}

Answer 1

The problem isn't in the row, it's in the column.

Couldn't read row 3, **col -1** from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.

It's basically saying that your MediaColumns.TITLE column doesn't exist in the cursor. Which is true. It's not in your first cursor (the one that it is referencing). Your other cursors are all within if statements so go out of scope and leave only the first one.

You can either re-pull the cursor like you do in the other portions of the if statement, or find some way to persist the cursor you got from the last if statement.

EDIT

It's pretty simple to fix, make the cursor a class variable. Also, I wouldn't keep re-using "cursor". Label them somethign individual and descriptive, it'll help you maintain readability in your code. I might do it like this:

public class MusicFlipper extends Activity implements OnItemClickListener {
    private Cursor artistCursor;
    private Cursor albumCursor;

Then you call them like you were but use the individual names.

albumCursor = managedQuery(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
                columns, where, whereVal, orderBy);

Since you declared it as a class variable it will be available through the whole class so in the last part you'd do:

if (currentList.equals("Songs")) {
    if (albumCursor.moveToPosition(position)) {
            String title = albumCursor.getString(albumCursor.getColumnIndex(MediaColumns.TITLE));
            TextView myTextView = (TextView) findViewById(R.id.title);
            myTextView.setText(title);
    }
}