public void onTextChanged(CharSequence s, int start, int before, int count) {
   if (s.length() > 1) {
      insertString = s.toString();
      new YourTask().execute(insertString);
   }
}

protected List<String> doInBackground() {
   // fetchning data from MySQL
   return list;
}

public void onPostExecute(List<String> result) {
   if (!result.isEmpty()) {
       SomeAdapter adp = new SomeAdapter(context, layout, result);
       actv.setAdapter(adp);
   }
}

import android.content.Context;
import android.util.AttributeSet;
import android.widget.AutoCompleteTextView;

public class MyAutoCompleteTextView extends AutoCompleteTextView {

    public MyAutoCompleteTextView(Context context, AttributeSet attrs,
            int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void performFiltering(CharSequence text, int keyCode) {
        //Here the AutompleteTextView has determined that the list should be filtered
    }

}

AutoCompleteTextView txtSearch;
PeopleAdapter adapter;
List<People> mList;
TextView idd;
ImageView imgspn;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mList = retrievePeople();

    txtSearch = (AutoCompleteTextView) findViewById(R.id.txt_search);

    adapter = new PeopleAdapter(this, R.layout.activity_main, R.id.lbl_name, mList);
    txtSearch.setThreshold(1);
    txtSearch.setAdapter(adapter);

    idd = (TextView) findViewById(R.id.idd);
    imgspn = (ImageView) findViewById(R.id.imgspn);
    imgspn.setVisibility(View.INVISIBLE);

    txtSearch.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            String Name = mList.get(position).getId();
            idd.setText(Name);
        }
    });

}

private List<People> retrievePeople() {

    List<People> list = new ArrayList<People>();
    try {
        Class.forName("com.mysql.jdbc.Driver");
        Connection con = (Connection) DriverManager.getConnection("jdbc:mysql://182.160.119.77:3306/hrms", "root",
                "W1nd0wsL1ve");
        Statement st = (Statement) con.createStatement();
        ResultSet rs = (ResultSet) st.executeQuery(
                "select name,designation_name,id from umdlv_users ut,t_designation td where ut.designation_id = td.designation_id");
        while (rs.next()) {

            list.add(new People(rs.getString(1), rs.getString(2), rs.getString(3)));
        }
        rs.close();
        st.close();
        con.close();
    } catch (Exception e) {
    }
    return list;
}