Question

I am new to android programming and i am trying to develop this app to call the google maps services on an android phone, then access a web service to retrieve the value of latitude and longitude of stations that need to be plotted on the map.

Foll is the code, but when i run the app the program is non responsive, it plots only one annottation and tht too the panning and zooming event is really slow and sometimes the code gets stuck.

Please help with the solution.

OpenMap.java


public class OpenMap extends MapActivity 
{

private MapController mapController;
private MyLocationOverlay myLocation;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    // Get Mapping Controllers etc
    MapView mapView = (MapView) findViewById(R.id.map_view);
    mapController = mapView.getController();
    mapController.setZoom(1);
    mapView.setBuiltInZoomControls(true);

    // Add the MyLocationOverlay
    myLocation = new MyLocationOverlay(this, mapView);
    mapView.getOverlays().add(myLocation);

    myLocation.enableMyLocation();

    DemoOverlay demoOverlay = new DemoOverlay();
    mapView.getOverlays().add(demoOverlay);
    myLocation.runOnFirstFix(new Runnable() {
        public void run() {
            mapController.animateTo(myLocation.getMyLocation());
        }
    });
}

@Override
protected void onResume() {
    super.onResume();
    myLocation.enableMyLocation();
}

@Override 
protected void onPause() {
    super.onPause();
    myLocation.disableMyLocation();
}

@Override
protected boolean isRouteDisplayed() {
    // TODO Auto-generated method stub
    return false;
}

}

DemoOverlay.java

public class DemoOverlay extends Overlay
{
ArrayList<String> arrlat_long = new ArrayList<String>();
public static String str;
public static String str1;
String responseBody;
int n=0;
 String Url =   "http://hiscentral.cuahsi.org/webservices/hiscentral.asmx/GetSeriesCatalogForBox2";
 List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(5); 
 HttpClient httpclient = new DefaultHttpClient();   
   @Override
    public void draw(Canvas canvas, MapView mapView, boolean shadow)
   {
        super.draw(canvas, mapView, shadow);
        Projection projection = mapView.getProjection();
         if(!Url.endsWith("?"))
         {
                Url += "?";
         }

            int latSpan = mapView.getLatitudeSpan();
            int lngSpan = mapView.getLongitudeSpan();
            GeoPoint mapCenter = mapView.getMapCenter();
            int mapLeftGeo = mapCenter.getLongitudeE6() - (lngSpan / 2);
            int mapRightGeo = mapCenter.getLongitudeE6() + (lngSpan / 2);

            int mapTopGeo = mapCenter.getLatitudeE6() - (latSpan / 2);
            int mapBottomGeo = mapCenter.getLatitudeE6() + (latSpan / 2);

            GeoPoint geoPoint = this.getSampleLocation();


         nameValuePairs.add(new BasicNameValuePair("xmin", "-100"));
         nameValuePairs.add(new BasicNameValuePair("xmax", "-90"));
         nameValuePairs.add(new BasicNameValuePair("ymin", "40"));
         nameValuePairs.add(new BasicNameValuePair("ymax", "55"));
         nameValuePairs.add(new BasicNameValuePair("networkIDs", ""));
         nameValuePairs.add(new BasicNameValuePair("conceptKeyword", "precipitation"));
         nameValuePairs.add(new BasicNameValuePair("beginDate", "1/1/2009"));
         nameValuePairs.add(new BasicNameValuePair("endDate", "1/1/2010"));
         String paramString = URLEncodedUtils.format(nameValuePairs, "utf-8");
         Url += paramString;

  if ((geoPoint.getLatitudeE6() > mapTopGeo && geoPoint.getLatitudeE6() < mapBottomGeo)
                 && (geoPoint.getLongitudeE6() > mapLeftGeo && geoPoint.getLongitudeE6() < mapRightGeo)) 
              {
                    geoPoint = arrlat_long(n);
                    Point myPoint = new Point();
                    projection.toPixels(geoPoint, myPoint);

                    Bitmap marker = BitmapFactory.decodeResource(mapView.getContext().getResources(), R.drawable.markerblue);

                    canvas.drawBitmap(marker, myPoint.x - 15, myPoint.y - 30, null);
                }

   }

private GeoPoint getSampleLocation() 
    {
       GeoPoint sampleGeoPoint;
      // int n=0;

       try {
              HttpPost httppost = new HttpPost(Url); 
              httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
              HttpResponse response = httpclient.execute(httppost);
              responseBody = EntityUtils.toString(response.getEntity());

            XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
            factory.setValidating(false);
            XmlPullParser myxml = factory.newPullParser();
            InputStream raw = new ByteArrayInputStream(responseBody.getBytes());
            myxml.setInput(raw, null);

            int eventType = myxml.getEventType();
            while(eventType != XmlPullParser.END_DOCUMENT) 
            {
                if(eventType == XmlPullParser.START_DOCUMENT) 
                {

                    Log.d("ParseXmlActivity", "In start document");
                }
                else if(eventType == XmlPullParser.START_TAG) 
                {
                    if (myxml.getName().equals("latitude"))
                    {
                        str="";
                        str  += "Lat:" + myxml.nextText().toString();
                         Log.d("ParseXmlActivity", "In start tag = "+str);
                         arrlat_long.add(str);
                    }
                    if (myxml.getName().equals("longitude"))
                    {
                        str1 += "--Lon:" + myxml.nextText().toString();
                         Log.d("ParseXmlActivity", "In start tag = "+str1);
                         arrlat_long.add(str1);
                    }
                } 
                eventType = myxml.next();

            }
        } 
        catch (XmlPullParserException e) 
        {
        } 
        catch (IOException e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


   int in =Integer.parseInt(str);
       int in1 =Integer.parseInt(str1);   
       sampleGeoPoint = new GeoPoint(in,in1);
        return sampleGeoPoint;
    }}

Answer 1

I think your approach is the wrong way to do it. I cannot rewrite you the whole code, but will give you some hints, how to do it. By the way, it has absolutly nothing to do, with google apis, its you, who is speaking to webservices inside the onDraw method of the Foreground Thread (aka UI-Thread)!

So to get off that, I would suggest the following:
Absolutely avoid to do heavy computing inside onDraw(Canvas). Use an AsyncTask , to gather your data. After your request, you could update your MapView by calling postInvalidate() and take that to draw.

Maybe the LazyLoad-feature of overlaymanager lib is interesting for you