Duplicate contacts issue when retrieving contacts

Question

I just want to invite friends to my application so that they can use the application too. For this i get all the contacts but the problem is contacts are repeating. Some contacts are showing 2 times and some are 3 and 4 times. I think i should a query "group by" so that no duplicates will be shown but I am confused where to put that query. Here is my code:

private ArrayList<String> conNames;
private ArrayList<String> conNumbers;
private Cursor crContacts;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.invite);
    conNames = new ArrayList<String>();
    conNumbers = new ArrayList<String>();

    crContacts = ContactHelper.getContactCursor(getContentResolver(), "");
    crContacts.moveToFirst();

    while (!crContacts.isAfterLast()) {
        conNames.add(crContacts.getString(1));
        conNumbers.add(crContacts.getString(2));
        crContacts.moveToNext();
    }

    setListAdapter(new MyAdapter(this, android.R.layout.simple_list_item_1,
            R.id.tvNameMain, conNames));

}

private class MyAdapter extends ArrayAdapter<String> {

    public MyAdapter(Context context, int resource, int textViewResourceId,
            ArrayList<String> conNames) {
        super(context, resource, textViewResourceId, conNames);

    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View row = setList(position, parent);
        return row;
    }

    private View setList(int position, ViewGroup parent) {
        LayoutInflater inf = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View row = inf.inflate(R.layout.liststyle, parent, false);

        TextView tvName = (TextView) row.findViewById(R.id.tvNameMain);
        final TextView tvNumber = (TextView) row.findViewById(R.id.tvNumberMain);
    tvName.setText(conNames.get(position));
        tvNumber.setText(conNumbers.get(position));
        return row;
    }
}

Guide me what to do avoid duplicate contacts

Answer 1

@Arslan Ali

If you don't want duplicates in a Collection, you should consider using HashMap. It does not allow duplicate keys however it allows to have duplicate values. So since your fetching the contacts name and number. Number will always be unique so make number your key and name as your value.

so in your case

Map<String, String> hm = new HashMap<String, String>();

while (!crContacts.isAfterLast()) {
        hm.put(crContacts.getString(2),crContacts.getString(1));
        crContacts.moveToNext();
}

So this way you will never have repetitive contacts. Now iterate through you HashMap and then push your key value to conNumbers and name value to conNames

for (String key : hm.keySet()) {
   conNames.add(key);
   conNumbers.add(hm.get(key));
}

And you got your unique Arraylist.