Android: How to requery a Cursor to refresh ListView after deleting database row?

Question

This might be a noob question but I'm quite new to all this SQLite-Database-Cursor-Adapter-ListView-Do-It-Properly-Stuff.

What I have:

In my MainActivity I have a ListView. I use an SQLite database and populate the ListView with a custom adapter extending SimpleCursorAdapter. By clicking on an item in my ActionBar I activate Contextual Action Mode. Everything is working so far.

What I want:

By clicking on a certain icon in my ListView item the according database row should be deleted and the ListView should be refreshed.

My question:

How do I refresh my Cursor and my ListView properly? When I don't use cursor.requery() in my OnClickListener and use cursor = dbm.getIOIOSensorsCursor() instead I get a CursorIndexOutOfBoundsException a few rows below at the line

int state = cursor.getInt(cursor.getColumnIndex(IOIOSensorSchema.STATE));

My app crashes, but after reloading it the database has been deleted and the according ListView item is gone.

I guess the crash must have something to do with _position in get getView method because _position is final. However, when I use cursor.requery() everything works as it should.

But this method is deprecated and it's documentation says "Don't use this...". I'm a friend of coding properly (I'm still a beginner and want to learn to code the right way and not quick-and-dirty) and want to know how to do this right. I don't know if it's important but I'm testing my app only on my (really fast) Nexus 4. There seem to be no problems with refreshing the Cursor fast enough, but I wonder if it will work on slower devices. In case it's important for you my database will contain about 10-20 rows with about 12 columns. I guess this is a really small database.

Here is the relevant code of my custom adapter:

public class IOIOSensorCursorAdapterCam extends SimpleCursorAdapter
{
static class ViewHolder
{
ImageView stateIV, removeIV;
TextView nameTV, pinNumberTV, feedIDTV, freqTV;
}

private Context ctx;
private Cursor cursor;
private IodDatabaseManager dbm;

public IOIOSensorCursorAdapterCam(Context _context, int _layout,
    Cursor _cursor, String[] _from, int[] _to, int _flags)
{
super(_context, _layout, _cursor, _from, _to, _flags);
ctx = _context;
cursor = _cursor;
dbm = new IodDatabaseManager(_context);
}

@Override
public View getView(final int _position, View _convertView,
    ViewGroup _parent)
{
ViewHolder holder = null;

LayoutInflater inflater = (LayoutInflater) ctx
    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

// There is no view at this position, we create a new one. In this case
// by inflating an xml layout.
if (_convertView == null)
{
    // Inflate a layout
    _convertView = inflater.inflate(R.layout.listview_item_sensor_cam,
        null);

    holder = new ViewHolder();
    holder.stateIV = (ImageView) _convertView
        .findViewById(R.id.stateImageView);
    holder.nameTV = (TextView) _convertView
        .findViewById(R.id.sensorNameTextView);
    holder.pinNumberTV = (TextView) _convertView
        .findViewById(R.id.sensorPinNumberTextView);
    holder.feedIDTV = (TextView) _convertView
        .findViewById(R.id.sensorFeedIDTextView);
    holder.freqTV = (TextView) _convertView
        .findViewById(R.id.sensorFrequencyTextView);
    holder.removeIV = (ImageView) _convertView
        .findViewById(R.id.removeImageView);
    _convertView.setTag(holder);
}
// We recycle a View that already exists.
else
{
    holder = (ViewHolder) _convertView.getTag();
}

// Set an OnClickListener to the "Delete Icon"
holder.removeIV.setOnClickListener(new OnClickListener()
{
    @SuppressWarnings("deprecation")
    @Override
    public void onClick(View _view)
    {
    cursor.moveToPosition(_position);

    // Delete sensor from database here
    int sensorID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.SENSOR_ID));
    dbm.deleteIOIOSensor(sensorID);

    // This leads to a "CursorIndexOutOfBoundsException" and cannot
    // be used to refresh the ListView
//      cursor = dbm.getIOIOSensorsCursor();

    // Refresh ListView
    cursor.requery();
    notifyDataSetChanged();
    }
});

cursor.moveToPosition(_position);

if (cursor.getCount() > 0)
{
    int state = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.STATE));

    if (state == 0)
    {
    holder.stateIV.setImageResource(R.drawable.av_play_over_video);
    holder.stateIV.setColorFilter(ctx.getResources().getColor(
        R.color.hint_lighter_gray));
    // _convertView.setAlpha((float) 0.5);
    holder.nameTV.setTextColor(ctx.getResources().getColor(
        R.color.hint_darker_gray));
    }
    else
    {
    holder.stateIV.setImageResource(R.drawable.av_pause_over_video);
    holder.stateIV.setColorFilter(ctx.getResources().getColor(
        android.R.color.holo_green_light));
    // _convertView.setAlpha((float) 1);
    holder.nameTV.setTextColor(ctx.getResources().getColor(
        android.R.color.black));
    }

    // Set the sensor's name to the according TextView
    String sensorName = cursor.getString(cursor
        .getColumnIndex(IOIOSensorSchema.NAME));
    holder.nameTV.setText(sensorName);

    // Set the sensor's pin number to the according TextView
    int pinNumber = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.PIN_NUMBER));
    holder.pinNumberTV.setText("" + pinNumber);

    // Set the sensor's feed ID to the according TextView
    int feedID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.FEED_ID));
    holder.feedIDTV.setText("" + feedID);

    // Set the sensor's frequency to the according TextView
    int frequency = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.FREQUENCY));
    int timeUnit = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.TIME_UNIT));
    String frequencyTextViewText = "";
    switch (timeUnit)
    {
    case IodIOIOSensor.TIME_UNIT_MINUTES:
    frequencyTextViewText = frequency + " min";
    break;
    case IodIOIOSensor.TIME_UNIT_HOURS:
    frequencyTextViewText = frequency + " h";
    break;
    default:
    frequencyTextViewText = frequency + " sec";
    break;
    }
    holder.freqTV.setText(frequencyTextViewText);
}
return _convertView;
}
}

Edit:

Here is my relevant code from the OnCickListener after implementing the solution:

// Set an OnClickListener to the "Delete Icon"
holder.removeIV.setOnClickListener(new OnClickListener()
{
    @Override
    public void onClick(View _view)
    {
    cursor.moveToPosition(_position);

    // Delete sensor from database here
    int sensorID = cursor.getInt(cursor
        .getColumnIndex(IOIOSensorSchema.SENSOR_ID));
    dbm.deleteIOIOSensor(sensorID);

    Toast.makeText(ctx, R.string.toast_sensor_deleted,
        Toast.LENGTH_SHORT).show();

    // Refresh ListView
    cursor = dbm.getIOIOSensorsCursor();
    swapCursor(cursor);

    notifyDataSetChanged();
    }
});

Answer 1

How do I refresh my Cursor and my ListView properly?

You "refresh [your] Cursor" by running your code again to get the Cursor, using the code you used to create the original Cursor (on a background thread, please). You refresh your ListView by calling changeCursor() or swapCursor() on the CursorAdapter.