Question

I have an application, which uses a custom implementation of MyLocationOverlay.

In the implementation I set a Bitmap property that is used when it has been specified, by an overload of Draw.

It works nicely, using my custom image, but it doesn’t display a shadow – as is done automatically in an ItemizedOverlay.

Can anyone help?

Here is (the relevant code from) my class:

public class LocationOverlay: MyLocationOverlay
{
    /// <summary>Bitmap to use for indicating the current fixed location.</summary>
    public Bitmap LocationMarker { get; set; }

    /// <summary>Uses the custom marker bitmap if one has been specified. Otherwise, the default is used.</summary>
    /// <param name="canvas"></param>
    /// <param name="mapView"></param>
    /// <param name="shadow"></param>
    /// <param name="when"></param>
    /// <returns></returns>
    public override bool Draw(Canvas canvas, MapView mapView, bool shadow, long when)
    {
        var drawShadow = shadow;

        if (LocationMarker != null && LastFix != null)
        {
            var screenPoint = new Point();
            var geoPoint = new GeoPoint((int)(LastFix.Latitude * 1E6), (int)(LastFix.Longitude * 1E6));
            mapView.Projection.ToPixels(geoPoint, screenPoint);
            canvas.DrawBitmap(LocationMarker, screenPoint.X, screenPoint.Y - 32, null);
            drawShadow = true;
        }

        base.Draw(canvas, mapView, drawShadow);
        return true;
    }
}

Answer 1

Got it. You can use DrawAt to draw the shadow automatically.

So my property becomes a Drawable thusly:

public Drawable MarkerResource
{
    set
    {
        _locationMarker = value;
        var widthOffset = _locationMarker.IntrinsicWidth / 2;
        _locationMarker.SetBounds(-widthOffset, -_locationMarker.IntrinsicHeight, widthOffset, 0);
    }
}

And the override now looks like this:

public override bool Draw(Canvas canvas, MapView mapView, bool shadow, long when)
{
    if (LastFix == null) return false;

    if (_locationMarker != null)
    {
        var screenPoint = new Point();
        var geoPoint = new GeoPoint((int)(LastFix.Latitude * 1E6), (int)(LastFix.Longitude * 1E6));
        mapView.Projection.ToPixels(geoPoint, screenPoint);
        DrawAt(canvas, _locationMarker, screenPoint.X, screenPoint.Y, shadow);
    }
    else if (MyLocation != null) DrawMyLocation(canvas, mapView, LastFix, MyLocation, when);

    if (IsCompassEnabled) DrawCompass(canvas, Orientation);
    return false;
}

Works perfectly.

This also now respects enabling the compass and will draw using the default technique if no Drawable is specified.