How to sort ArrayAdapter<String> in Android?

Question

I am tryign to populate an ExpandableList items in android. Currently, I am getting the values of the headers from a string-array from the resources as follow:

String[] processesValues = context.getResources().getStringArray(R.array.processes);

Then I sort the Array using the following:

Arrays.sort(processesValues);

Afterward, I am loading the Array in the ArrayAdaptor list as follow:

ArrayAdapter<String> processesAdaptor = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, processesValues);

Now, the headers Array is sorted alphabetically, but the ArrayAdaptor list are not sorted. for example, if I have the following string-array in resouces:

<string-array name="processes">
    <item>cab</item>
    <item>abc</item>
    <item>bac</item>
</string-array>

I get and sort the Array like this:

> abc
> bac
> cab

then i try to put it in the ArrayAdapter, but the ArrayAdaptor show the following headers when running the app:

> cab
> abc
> bac

what am I doing wrong ?

UPDATE

here is my full code:

public class ExpandableListDataPump {

private static Context context;

public ExpandableListDataPump(Context current) {
    this.context = current;
}

public static HashMap<String, List<String>> getData() {

    String[] placesValues;

    Comparator<String> ALPHABETICAL_ORDER1 = new Comparator<String>() {
        public int compare(String object1, String object2) {
            int res = String.CASE_INSENSITIVE_ORDER.compare(object1.toString(), object2.toString());
            return res;
        }
    };


    placesValues = context.getResources().getStringArray(R.array.places);
    ArrayAdapter<String> locationsAdaptor = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList1 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor.getCount(); i++) {
        locationsList1.add((String) locationsAdaptor.getItem(i));
        Collections.sort(locationsList1, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places2);
    ArrayAdapter<String> locationsAdaptor2 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList2 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor2.getCount(); i++) {
        locationsList2.add((String) locationsAdaptor2.getItem(i));
        Collections.sort(locationsList2, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places3);
    ArrayAdapter<String> locationsAdaptor3 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList3 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor3.getCount(); i++) {
        locationsList3.add((String) locationsAdaptor3.getItem(i));
        Collections.sort(locationsList3, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places4);
    ArrayAdapter<String> locationsAdaptor4 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList4 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor4.getCount(); i++) {
        locationsList4.add((String) locationsAdaptor4.getItem(i));
        Collections.sort(locationsList4, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places5);
    ArrayAdapter<String> locationsAdaptor5 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList5 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor2.getCount(); i++) {
        locationsList5.add((String) locationsAdaptor5.getItem(i));
        Collections.sort(locationsList5, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places6);
    ArrayAdapter<String> locationsAdaptor6 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList6 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor2.getCount(); i++) {
        locationsList6.add((String) locationsAdaptor6.getItem(i));
        Collections.sort(locationsList6, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places7);
    ArrayAdapter<String> locationsAdaptor7 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList7 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor7.getCount(); i++) {
        locationsList7.add((String) locationsAdaptor7.getItem(i));
        Collections.sort(locationsList7, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places8);
    ArrayAdapter<String> locationsAdaptor8 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList8 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor8.getCount(); i++) {
        locationsList8.add((String) locationsAdaptor8.getItem(i));
        Collections.sort(locationsList8, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places9);
    ArrayAdapter<String> locationsAdaptor9 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList9 = new ArrayList<String>();
    for (int i = 0; i < locationsAdaptor9.getCount(); i++) {
        locationsList9.add((String) locationsAdaptor9.getItem(i));
        Collections.sort(locationsList9, ALPHABETICAL_ORDER1);
    }

    // -----------

    placesValues = context.getResources().getStringArray(R.array.places10);
    ArrayAdapter<String> locationsAdaptor10 = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, placesValues);
    List<String> locationsList10 = new ArrayList<String>();
    String placesValuesString10 = null;
    for (int i = 0; i < locationsAdaptor10.getCount(); i++) {
        locationsList10.add((String) locationsAdaptor10.getItem(i));
        Collections.sort(locationsList10, ALPHABETICAL_ORDER1);
    }

    // -----------

    List<List<String>> allLocationLists = new ArrayList<List<String>>();
    allLocationLists.add(locationsList1);
    allLocationLists.add(locationsList2);
    allLocationLists.add(locationsList3);
    allLocationLists.add(locationsList4);
    allLocationLists.add(locationsList5);
    allLocationLists.add(locationsList6);
    allLocationLists.add(locationsList7);
    allLocationLists.add(locationsList8);
    allLocationLists.add(locationsList9);
    allLocationLists.add(locationsList10);

    // ----------------

    HashMap<String, List<String>> expandableListDetail = new HashMap<String, List<String>>();

    String[] processesValues = context.getResources().getStringArray(R.array.processes);
    Arrays.sort(processesValues);

    ArrayAdapter<String> processesAdaptor = new ArrayAdapter<String>(context,
            R.layout.places_list_item, R.id.placeNameTv, processesValues);

    processesAdaptor.setNotifyOnChange(true);

    for (int i = 0; i < processesAdaptor.getCount(); i++) {
        String test = processesAdaptor.getItem(i).toString();
        System.out.println(test);
        expandableListDetail.put(processesAdaptor.getItem(i), allLocationLists.get(i));
    }

    return expandableListDetail;
}

}

Answer 1

Per the Android documentation, "setNotifyOnChange" will only trigger if you use the Adapter's functions to edit the list. You may need to call [youradapter].notifyDataSetChanged() after sorting.

https://developer.android.com/reference/android/widget/ArrayAdapter#setNotifyOnChange(boolean)