unexpected behavior of arrayadapter and nullpointer error

Question

I am using following code.

mDbHelper.open();
        String[] areasList = new String[51];
        for (int i = 0; i<51; i ++)
        {
            areasList[i] = "";
        }
        areasList = mDbHelper.getAllAreas();
        mDbHelper.close();

        ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, areasList);
        spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        chooseArea.setAdapter(spinnerArrayAdapter);

In debugger it shows all the values of String[] taken from database.

public String[] getAllAreas()
    {
        String[] areasList = new String[51];
        String queryString = "SELECT areaName FROM TFTaxi";
        Cursor resultSet =  mDb.rawQuery(queryString, null); 
        for (int i = 0; i<51; i ++)
        {
            areasList[i] = "";
        }
        int i = 1;
        areasList[0] = "Choose your Area";

        while(resultSet.moveToNext())
        {

            areasList[i] = resultSet.getString(resultSet.getColumnIndex("areaName"));
            i++;
        }

        resultSet.close();
        return areasList;
    }

But then it gives error

06-27 23:40:43.882: E/AndroidRuntime(16467): FATAL EXCEPTION: main
06-27 23:40:43.882: E/AndroidRuntime(16467): java.lang.NullPointerException
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:192)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.Spinner.onMeasure(Spinner.java:285)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:594)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:376)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:594)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:376)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2092)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.View.measure(View.java:12723)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1064)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.os.Looper.loop(Looper.java:137)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.app.ActivityThread.main(ActivityThread.java:4424)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at java.lang.reflect.Method.invokeNative(Native Method)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at java.lang.reflect.Method.invoke(Method.java:511)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

I think you skipped one result record by calling moveToNext before processing that record.

Assuming your query returns 50 records only try this change:

public String[] getAllAreas()
    {
        .....
        resultSet.moveToFirst();
        while(!resultSet.isAfterLast())
        {
            areasList[i] = resultSet.getString(resultSet.getColumnIndex("areaName"));
            i++;
            resultSet.moveToNext();
        }
        .........
    }

Answer 2

06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
06-27 23:40:43.882: E/AndroidRuntime(16467):    at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)

from above error it's clear the error is due to any of areasList[i] is null....see line 394

text.setText(item.toString());

• before iterating set cursor to first cursor.moveToFirst().

.

 cursor.moveToFirst();
        do {


        } while (cursor.moveToNext());

Answer 3

resultSet.moveToNext() - moves to next, so my guess would be you just skip the first item from the DB (even if cursor contains correct number of items - 50).

Try switching from precondition while(resultSet.moveToNext()) {} to postcondition do {} while(resultSet.moveToNext())