AutoCompleteView: Synchronous Server Call With Filter

In order to implement synchronous server calling within a filter, autocomplete textview is used. Web service is hit with each character typed in the Autocomplete list. For having data dynamically in the list, we can make a customized adapter. I have implemented it by making this adapter implement the filterable interface.

For getting data from the server, two approaches can be used:

1) Using the Volley Library

@Override
public Filter getFilter() {
Filter filter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint){
final FilterResults filterResults = new FilterResults();
if (constraint != null) {
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET,url,null,new com.android.volley.Response.Listener()
{
@Override
public void onResponse(JSONObject response) {
ResponseData responseData = new Gson().fromJson(response.toString(),ResponseData.class);
if(responseData != null){
filterResults.values = responseData.getResponseData();
filterResults.count = responseData.getResponseData().size();
}}},new com.android.volley.Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
@Override
public Map getHeaders() throws AuthFailureError {
return getCustomHeaders();
}};
}
return filterResults;
}

The volley request can be made inside the performFiltering() function, which gets a callback after each character is typed. But, the problem in this approach is due to asynchronous request. A different thread is started, and before getting any result, the execution of the performFiltering() function stops. So, we don't receive a result from the server or before the publishResults() function is called to display the result to UI.

2) Using Async Task

@Override
public Filter getFilter() {
Filter filter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
final FilterResults filterResults = new FilterResults();
if (constraint != null) {
Object obj = WebServiceManager.callWebService();
ResponseData responseData = new Gson().fromJson(obj.toString(),ResponseData.class);
if(responseData != null) {
filterResults.values = responseData.getResponseData();
filterResults.count = responseData.getResponseData().size();
}}
return filterResults;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
if (results != null && results.count > 0) {
resultList = (List) results.values;
notifyDataSetChanged();
} else {
notifyDataSetInvalidated();
}}};
return filter;
}

In WebServiceManager:

private static Object requestServer(String urlStr) {
HttpURLConnection httpURLConnection = null;
Object response = null;
InputStream inputStream;
int ch;
try{
URL url = new URL(urlStr);
httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setConnectTimeout( 3000 * 10000); //Timeout until a connection is established
httpURLConnection.setReadTimeout(3000 * 10000); //Timeout for waiting for data to come
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setRequestProperty("Content-Type", "application/json");
httpURLConnection.setDoInput(true);
httpURLConnection.connect();
inputStream = new BufferedInputStream( httpURLConnection.getInputStream());
StringBuffer stringBuffer = new StringBuffer();
while ((ch = inputStream.read()) != -1) {
stringBuffer.append((char) ch);
}
response = stringBuffer.toString();
}
catch (Exception exception) {
exception.printStackTrace();
}
finally {
httpURLConnection.disconnect();
}
return response;
}

Being the synchronous call, a call is made to the server and the results are obtained before the performFiltering() function stops executing. Congrats! The autocomplete list is obtained.