package com.dougkeen.bart; import java.io.IOException; import java.io.StringWriter; import java.io.UnsupportedEncodingException; import java.net.MalformedURLException; import org.apache.commons.io.IOUtils; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpUriRequest; import org.xml.sax.SAXException; import android.os.AsyncTask; import android.util.Log; import android.util.Xml; public abstract class GetRouteFareTask extends AsyncTask { private final static int MAX_ATTEMPTS = 5; private final static String FARE_URL = "http://api.bart.gov/api/sched.aspx?cmd=fare&date=today&key=" + Constants.API_KEY + "&orig=%1$s&dest=%2$s"; private Exception mException; private String fare; @Override protected String doInBackground(Params... paramsArray) { Params params = paramsArray[0]; if (!isCancelled()) { return getFareFromNetwork(params, 0); } else { return null; } } private String getFareFromNetwork(Params params, int attemptNumber) { String xml = null; try { HttpUriRequest request = new HttpGet( String.format(FARE_URL, params.origin.abbreviation, params.destination.abbreviation)); FareContentHandler handler = new FareContentHandler(); if (isCancelled()) { return null; } HttpResponse response = NetworkUtils.executeWithRecovery(request); if (response.getStatusLine().getStatusCode() != HttpStatus.SC_OK) { throw new IOException("Server returned " + response.getStatusLine().toString()); } StringWriter writer = new StringWriter(); IOUtils.copy(response.getEntity().getContent(), writer, "UTF-8"); xml = writer.toString(); if (xml.length() == 0) { throw new IOException("Server returned blank xml document"); } Xml.parse(xml, handler); fare = handler.getFare(); return fare; } catch (MalformedURLException e) { throw new RuntimeException(e); } catch (UnsupportedEncodingException e) { throw new RuntimeException(e); } catch (IOException e) { if (attemptNumber < MAX_ATTEMPTS - 1) { try { Log.w(Constants.TAG, "Attempt to contact server failed... retrying in 3s", e); Thread.sleep(3000); } catch (InterruptedException interrupt) { // Ignore... just go on to next attempt } return getFareFromNetwork(params, attemptNumber + 1); } else { mException = new Exception("Could not contact BART system", e); return null; } } catch (SAXException e) { mException = new Exception( "Could not understand response from BART system: " + xml, e); return null; } } public static class Params { public Params(Station origin, Station destination) { super(); this.origin = origin; this.destination = destination; } public final Station origin; public final Station destination; } @Override protected void onPostExecute(String result) { if (result != null) { onResult(fare); } else { onError(mException); } } public abstract void onResult(String fare); public abstract void onError(Exception exception); }