Drawing transparent on a MapView

Question

I am currently drawing lines on a MapView based on different GeoPoints to indicate sectors. With the following code (this is within an overlay):

@Override
public void draw(Canvas canvas, MapView mapView, boolean shadow)
{
    for(Polygon polygonTemp : polygonList)
    {           
        Path p = new Path();
        Projection projection = mapView.getProjection();

        boolean firstTime = true;
        for(GeoPoint geoPoint : polygonTemp.getGeoPointList())
        {
            Point drawPoint = new Point();
            projection.toPixels(geoPoint, drawPoint);

            if(firstTime)
            {
                p.moveTo(drawPoint.x, drawPoint.y);
                firstTime = false;
            }
            else
            {
                p.lineTo(drawPoint.x, drawPoint.y);
            }
        }
        p.setFillType(Path.FillType.EVEN_ODD);

        Paint polyPaint = new Paint();
        polyPaint.setStrokeWidth(1);
        polyPaint.setStyle(Paint.Style.FILL_AND_STROKE);
        polyPaint.setAntiAlias(true);
        polyPaint.setColor(Color.parseColor(polygonTemp.getColor()));
        canvas.drawPath(p, polyPaint);
        firstTime = true;
    }
    super.draw(canvas, mapView, shadow);
}

The problem is, I want them to be filled with some degree of transparency, so I can still see the map under the filled sectors. I tried to set polyPaint.setAlpha(), even to 255 (which should be completely transparent) and it doesn't do anything, it's completely opague.

Anyone knows what I'm doing wrong?

Answer 1

I don't see where you are setting the alpha. Regardless 255 is not transparent, it is opaque.

FYI, I am doing identical things (drawing paths on map overlays) and this works fine for drawing a 50% opaque, red line:

mPaint.setColor(Color.parseColor ("#88ff0000"));