[Android] MapView ConcurrentModificationException

Question

Hello everyone,

As the title suggest i have (sometimes) a concurrentmodificationexception while trying to create a route between two locations ... Here is my code (and in case you're wondering MyOverlay does not try to access the other Overlays in the map)

    private class fillRouteTask extends AsyncTask<Void, GeoPoint, Void> {

  /**
   * create the url to call to get the route
   * 
   * @param src
   * @param dest
   * @return
   */
  private StringBuilder createUrl(GeoPoint src, GeoPoint dest) {
   // connect to map web service
   StringBuilder urlString = new StringBuilder();
   urlString.append("http://maps.google.com/maps?f=d&amp;hl=en");
   urlString.append("&saddr=");// from
   urlString.append(Double
     .toString((double) src.getLatitudeE6() / 1.0E6));
   urlString.append(",");
   urlString.append(Double
     .toString((double) src.getLongitudeE6() / 1.0E6));
   urlString.append("&daddr=");// to
   urlString.append(Double
     .toString((double) dest.getLatitudeE6() / 1.0E6));
   urlString.append(",");
   urlString.append(Double
     .toString((double) dest.getLongitudeE6() / 1.0E6));
   urlString.append("&ie=UTF8&0&om=0&output=kml");
   Log.d("xxx", "URL=" + urlString.toString());

   return urlString;
  }

  /**
   * create the connection to google url
   * 
   * @param src
   * @param dest
   * @return
   */
  private String connectToUrl(GeoPoint src, GeoPoint dest) {

   // get the kml (XML) doc. And parse it to get the
   // coordinates(direction
   // route).
   Document doc = null;
   HttpURLConnection urlConnection = null;
   URL url = null;
   try {
    url = new URL(createUrl(src, dest).toString());
    urlConnection = (HttpURLConnection) url.openConnection();
    urlConnection.setRequestMethod("GET");
    urlConnection.setDoOutput(true);
    urlConnection.setDoInput(true);
    urlConnection.connect();

    DocumentBuilderFactory dbf = DocumentBuilderFactory
      .newInstance();
    DocumentBuilder db = dbf.newDocumentBuilder();
    doc = db.parse(urlConnection.getInputStream());

    if (doc.getElementsByTagName("GeometryCollection") != null
      && doc.getElementsByTagName("GeometryCollection")
        .getLength() > 0) {
     return doc.getElementsByTagName("GeometryCollection").item(
       0).getFirstChild().getFirstChild().getFirstChild()
       .getNodeValue();
    }

   } catch (MalformedURLException e) {
    Log.d("test", e.getLocalizedMessage());
   } catch (IOException e) {
    Log.d("test", e.getLocalizedMessage());
   } catch (ParserConfigurationException e) {
    Log.d("test", e.getLocalizedMessage());
   } catch (SAXException e) {
    Log.d("test", e.getLocalizedMessage());
   }
   return null;
  }

  protected Void doInBackground(Void... arg0) {
   try {
    // get the current overlays present in the map
    List<Overlay> overs = Collections.synchronizedList(mapView
      .getOverlays());
    String path = connectToUrl(orig, dest);
    if (path != null) {
     Log.d("xxx", "path=" + path);
     String[] pairs = path.split(" ");
     String[] lngLat = pairs[0].split(",");

     GeoPoint startGP = new GeoPoint((int) (Double
       .parseDouble(lngLat[1]) * 1E6), (int) (Double
       .parseDouble(lngLat[0]) * 1E6));

     overs.add(new MyOverlay(startGP, startGP, 1));
     GeoPoint gp1;
     GeoPoint gp2 = startGP;
     for (int i = 1; i < pairs.length; i++) // the last one would
     // be
     // crash
     {
      lngLat = pairs[i].split(",");
      gp1 = gp2;
      // watch out! For GeoPoint, first:latitude,
      // second:longitude
      gp2 = new GeoPoint(
        (int) (Double.parseDouble(lngLat[1]) * 1E6),
        (int) (Double.parseDouble(lngLat[0]) * 1E6));
      Log.d("xxx", "pair:" + pairs[i]);
      publishProgress(gp1, gp2);
     }
     overs.add(new MyOverlay(dest, dest, 3)); // use
     // the
     // default
     // color
     drawn = false;
    } else {
     m_handler.post(new Runnable() {

      public void run() {
       Toast.makeText(getApplicationContext(),
         "Problem in getting the directions",
         Toast.LENGTH_SHORT).show();
      }
     });
    }
   } catch (Exception e) {
    m_handler.post(new Runnable() {

     public void run() {
      Toast.makeText(getApplicationContext(),
        R.string.errorrouteLoad, Toast.LENGTH_LONG)
        .show();
     }
    });
   }
   return null;

  }

  /*
   * (non-Javadoc)
   * 
   * @see android.os.AsyncTask#onProgressUpdate(Progress[])
   */
  @Override
  protected void onProgressUpdate(GeoPoint... values) {
   // TODO Auto-generated method stub
   List<Overlay> overs = Collections.synchronizedList(mapView
     .getOverlays());
   overs.add(new MyOverlay(values[0], values[1], 2, 0x0000ff));

  }

  /*
   * (non-Javadoc)
   * 
   * @see android.os.AsyncTask#onPostExecute(java.lang.Object)
   */
  @Override
  protected void onPostExecute(Void result) {
   // TODO Auto-generated method stub
   Log.d("routing", "done");
   mapView.postInvalidate();
  }
 }

Answer 1

You can only modify overlays on the UI thread. You need to add the new data to the overlay in the onPostExecute method of AsyncTask.