[android-developers] Re: Maps API : drawing driving itinerary

No need to worry about the screen pixels relative to your waypoints. The overlay manager handles that for you, and only renders the part that is on screen. Load all the points.

On Thursday, May 17, 2012 12:19:33 PM UTC-4, Simon Giddings wrote:

I am developing a maps application which will display a user defined driving itinerary.
I obtain the driving directions from the Directions Web Service and parse the json response in a separate thread.

I then hand the resulting itinerary object to my custom overlay for display.
Before appending the overlay to the maps overlay list, I decode the polyline strings to obtain the coordinates.

My drawing code obtains the projection object and draws out the line - this is taking 18 seconds ! ! !
Here is my code :

    @Override
    public void draw(Canvas cv, MapView view, boolean shadow)
    {
        GeoCoordsE6 point = null;  // utility class holding a geopoint and a point class with a method to handle projection manipulation
        int iScreenWidth = view.getWidth();
        int iScreenHeight = view.getHeight();
        Paint paintLine = null;new Paint();
       
        if(shadow)
        {
            super.draw(cv, view, shadow);
            return;
        }
       
        long lStartMs = android.os.SystemClock.uptimeMillis();
       
        paintLine = new Paint();
        paintLine.setColor(m_iLineClr);
        paintLine.setAntiAlias(true);
        paintLine.setStyle(Paint.Style.FILL_AND_STROKE);
        paintLine.setStrokeJoin(Paint.Join.ROUND);
        paintLine.setStrokeCap(Paint.Cap.ROUND);
        paintLine.setStrokeWidth(4);
       
        // get the projection to work with
        Projection pj = view.getProjection();
       
        // get the first lat/lng position
        point = m_ItinLine.item(0);
        // convert the coorinates to screen pixels
        point.ResolvePosition(pj);
        // store the start position
        m_ptStart.x = point.m_pt.x;
        m_ptStart.y = point.m_pt.y;
       
        // now walk through the array list
        for(int i = 1; i < m_ItinLine.count(); i++)
        {
            point = m_ItinLine.item(i);
            point.ResolvePosition(pj);
            m_ptEnd.x = point.m_pt.x;
            m_ptEnd.y = point.m_pt.y;
           
            if(m_ptStart.x < 0 && m_ptEnd.x < 0 ||        // to the left
                    m_ptStart.y < 0 && m_ptEnd.y < 0 ||    // above the top
                    m_ptStart.x > iScreenWidth && m_ptEnd.x > iScreenWidth ||    // to the right
                    m_ptStart.y > iScreenHeight && m_ptEnd.y > iScreenHeight)    // below the bottom
            {
                // ignore the drawing
            }
            else if(m_ptStart.x == m_ptEnd.x && m_ptStart.y == m_ptEnd.y)
                continue;
            else
            {
                cv.drawLine(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y, paintLine);
            }
           
            m_ptStart.x = m_ptEnd.x;
            m_ptStart.y = m_ptEnd.y;
        }
       
        long lEndMs = android.os.SystemClock.uptimeMillis();
        Log.d("ItineraryOverlay", "Drawing took " + (lEndMs - lStartMs) + "ms");
       
        super.draw(cv, view, shadow);
    }

Knowing that a number of people have done similar tasks, can anyone advise me as to how to improve the performance ?
Should I be building a path object and fill it with ALL of the points ?

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