Loading GeoPoints / Path on MapView is taking forever. Any way to speed it up?

Question

I am working with a custom MapView for an application. I have a database with a LOT of GPS datapoints saved and I am currently loading them using Overlays, then performing an .addAll on the MapView with the Overlays.

However, it is taking up to 2 minutes to load just a few hundred data points as a path on the MapView.

The code to load the Data Points is:

    private void loadMap() {        
    //Load the specific data from the database
    DBAdapter db = new DBAdapter(this);
    try {
        db.open();
        Cursor mDataPoints = db.db.rawQuery("SELECT * FROM GPS_DATA)", null);
        if ((mDataPoints != null) && (!mDataPoints.isClosed()) && (mDataPoints.moveToFirst())) {                
            mapMain.setFinishedLoading(false);
            mapMain.getOverlays().clear();

            if ((!mDataPoints.isClosed()) && (mDataPoints.moveToFirst())) {
                while (!mDataPoints.isAfterLast()) {

                    this.drawPath(db, 
                                  DBAdapter.formatLong(mDataPoints, "data_id"), 
                                  DBAdapter.formatString(mDataPoints, "data_name"),
                                  DBAdapter.formatString(mDataPoints, "data_type"));                        

                    mDataPoints.moveToNext();
                }
            }

            mapMain.refreshDrawableState();
            mapMain.setEnabled(true);
        }
    } finally {
        db.close();
    }
}

public void drawPath(DBAdapter db, long pDataID, String pDataName, String pDataType) {  

    Cursor mData = db.getPointDataByDataID(pDataID);
    if ((!mData.isClosed()) && (mData.moveToFirst())) {
        boolean vFirst = true;
        int i = 0;
        GeoPoint startGP;
        GeoPoint geoPoint1;
        GeoPoint geoPoint2 = null;

        while (!mData.isAfterLast()) {
            if (vFirst) {
                startGP = new GeoPoint((int) (DBAdapter.formatDouble(mData, "latitude") * 1E6), (int) (DBAdapter.formatDouble(mData, "longitude") * 1E6));
                mapMain.getOverlays().add(new Map_Route_Overlay(startGP, startGP, this.returnPathColor(pDataType), pDataName));
                vFirst = false;
                geoPoint2 = startGP;
            } else {
                geoPoint1 = geoPoint2;

                geoPoint2 = new GeoPoint((int) (DBAdapter.formatDouble(mData, "latitude") * 1E6), (int) (DBAdapter.formatDouble(mData, "longitude") * 1E6));
                if (geoPoint2.getLatitudeE6() != 22200000) {
                    mapMain.getOverlays().add(new Map_Route_Overlay(geoPoint1, geoPoint2, this.returnPathColor(pDataType), pDataName));
                }
            }

            i += 1;
            mData.moveToNext();
        }

        if (geoPoint2 != null) { 
            mapMain.getOverlays().add(new Map_Route_Overlay(geoPoint2, geoPoint2, this.returnDataColor(pDataType), pDataName));
        }
    }
    mData.close();
}
public int returnDataColor(String pType) {
    int vReturnData = Color.BLUE;

    if (pType.trim().equals("S")) {
        vReturnData = Color.RED;
    }

    return vReturnData;
}

And the code for the Map_Route_Overlay class is:

public final class Map_Route_Overlay extends Overlay {
  private static String TAG = CoreFunctions.APP_TAG + "_MapRouteOverlay";

  private GeoPoint geoPoint1;
  private GeoPoint geoPoint2;
  private int defaultColor = 999;
  private String dataName = "";

  public Map_Route_Overlay(GeoPoint pGeoPoint1, GeoPoint pGeoPoint2, int pColor, String pText) {
    this.geoPoint1 = pGeoPoint1;
    this.geoPoint2 = pGeoPoint2;
    this.defaultColor = pColor;
    this.dataName = pText;
  }

  public void setDataName(String pName) {
    this.dataName = pName;
  }

  @Override
  public boolean draw (Canvas canvas, MMMapView mapView, boolean shadow, long when) {
    Projection projection = mapView.getProjection();
    if (shadow == false) {
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        Point point = new Point();
        projection.toPixels(this.geoPoint1, point);
        paint.setColor(this.defaultColor);
        Point point2 = new Point();
        projection.toPixels(this.geoPoint2, point2);
        paint.setStrokeWidth(2);
        paint.setAlpha(this.defaultColor == Color.parseColor("#6C8715")?220:120);
        canvas.drawLine(point.x, point.y, point2.x,point2.y, paint);
    }

    return super.draw(canvas, mapView, shadow, when);
  }

}

I have tried several options, including loading the data using Threads, but notifying the MapView to load the Overlays when completed was becoming a nightmare.

Just for reference, MMMapView is my custom MapView component, which for now just inherits MapView and implements two functions.

Answer 1

You really shouldn't be trying to display hundreds of Overlays on the screen at once, because you will get bad performance. Try limiting it to 10-20. Any more than that and it is too busy for the user anyway.

Also you should be using a thread to load the items from your database. What I do is I use a custom ItemizedOverlay, and add custom OverlayItems to it in a thread. Then once I am done loading I call mapView.postInvalidate(); so that they are displayed on the screen.