Question

I have written some code which should allow me to fetch all the data under a column in a database and store it in a string array. I the convert the string array containing the information into a double array. All of the values in the double array are there added together to get one total value and this value is then displayed in the EditText.
However whenever I start the activity an error appears saying java.lang.NullPointerException.

This is code for the arrays:

DatabaseTotalEntries getAllData = new DatabaseTotalEntries(this); //Creates a new method in the database class
    getAllData.open();
    String[] RunningCosts = getAllData.getCost(); //Transfers all the data under the Total Running Costs column into a String Array
    String[] RunningTimes = getAllData.getTime();
    String[] EnergyUsages = getAllData.getEnergy();
    getAllData.close();

    double[] doubleRunningCosts = new double[RunningCosts.length];
    for(int i=0; i<RunningCosts.length; i++)
    {
       doubleRunningCosts[i] = Double.parseDouble(RunningCosts[i]);
    } // Converts the string array 'RunningCosts' into a double array

    double TotalCost = 0;
    for (int in = 0; in <doubleRunningCosts.length; in++)
        TotalCost += doubleRunningCosts[in]; //Adds the values in the double string array together to get one total value

    DecimalFormat decf = new DecimalFormat("##");
    totalCostBox.setText(decf.format(TotalCost)); //Sets the variable 'TotalCost' to appear in the totalCostBox edit text

LogCat says the incident occurs at line 31, which is

double[] doubleRunningCosts = new double[RunningCosts.length];

This is the getData method I am using in my database:

public String[] getCost() {
    // TODO Auto-generated method stub
    ArrayList<String> costarraylist = new ArrayList<String>();
    String[] applianceCostcolumns = new String[] { KEY_TOTAL_COST };
    Cursor costcursor = allDatabase.query(DATABASE_TABLE, applianceCostcolumns, null, null, null, null, null);
    String result;

    int iApplianceCost = costcursor.getColumnIndex(KEY_TOTAL_COST);

    for (costcursor.moveToFirst(); !costcursor.isAfterLast(); costcursor
            .moveToNext()) {

        result = costcursor.getString(iApplianceCost);

        costarraylist.add(result);
    };
    return null;
}

Does anyone know what could be the problem? Thanks

Answer 1

Change

return null;

to

return costarraylist.toArray(new String[costarraylist.size()]);

on the last line of your getCost() method.