Getting a SUM value for a SQlite column and assigning it to Textview

I have an Android app that asks users to enter distance as a field. It is set as a SQLite REAL data type as I need a decimal place. I want to sum the column and display that to the user in a fragment as the Total distance they covered. I have a DBmanager with the code below. I'm not sure if that is the correct way to get a SUM value.

public Cursor Distance() {
        Cursor Distance = database.rawQuery("SELECT Sum(" + DatabaseHelper.DSNM + ") AS myTotal FROM " + DatabaseHelper.TABLE_NAME, null);
        return Distance;
}

I want to display the SUM value in a textView for which I have the code below. Could someone tell me where i'm going wrong? Thanks!

public class Summary extends Activity {
    private TextView tnmView;
    private DBManager dbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setTitle("Total Distance");
        setContentView(R.layout.fragment_summary);
        tnmView = (TextView) findViewById(R.id.tnmView);
        dbManager = new DBManager(this);
        dbManager.open();
        Cursor Distance = dbManager.Distance();
        tnmView.setText(nm);

    }
}