Draw circle of certain radius on map view in Android

In case someone was looking for an answer using Google Maps API v2, here's a snippet of what I did. It's really more of a geographical approach.

public class MapDrawer {

private GoogleMap map;
private static int EARTH_RADIUS = 6371000;

public MapDrawer(GoogleMap map) {
    this.map = map;
}

private LatLng getPoint(LatLng center, int radius, double angle) {
    // Get the coordinates of a circle point at the given angle
    double east = radius * Math.cos(angle);
    double north = radius * Math.sin(angle);

    double cLat = center.latitude;
    double cLng = center.longitude;
    double latRadius = EARTH_RADIUS * Math.cos(cLat / 180 * Math.PI);

    double newLat = cLat + (north / EARTH_RADIUS / Math.PI * 180);
    double newLng = cLng + (east / latRadius / Math.PI * 180);

    return new LatLng(newLat, newLng);
}

public Polygon drawCircle(LatLng center, int radius) {
    // Clear the map to remove the previous circle
    map.clear();
    // Generate the points
    List<LatLng> points = new ArrayList<LatLng>();
    int totalPonts = 30; // number of corners of the pseudo-circle
    for (int i = 0; i < totalPonts; i++) {
        points.add(getPoint(center, radius, i*2*Math.PI/totalPonts));
    }
    // Create and return the polygon
    return map.addPolygon(new PolygonOptions().addAll(points).strokeWidth(2).strokeColor(0x700a420b));
}

}

The good thing about this is that you don't have to redraw anything after zooming or panning the map - the circle gets resized and moved accordingly. The downside is that this doesn't work if you want a circle on either north or south pole - it'll all go bezerk, but, hopefully, that's not the case 99% of the time :)

Just to bring this up to date... they've made it very easy to do on Google Maps API v2.

    mMap.addCircle(new CircleOptions()
        .center(center)
        .radius(radius)
        .strokeWidth(0f)
        .fillColor(0x550000FF));

Where radius is in meters.

As for markers on the boundary, that should be relatively easy to do - just follow the 'Circles' Demo in the Google Maps sample code here: https://developers.google.com/maps/documentation/android/intro#sample_code

In the implementation of the ItemizedOverlay, do something like the method drawCircle from the onDraw method

protected void drawCircle(Canvas canvas, Point curScreenCoords) {
    curScreenCoords = toScreenPoint(curScreenCoords);
    int CIRCLE_RADIUS = 50;
    // Draw inner info window
    canvas.drawCircle((float) curScreenCoords.x, (float) curScreenCoords.y, CIRCLE_RADIUS, getInnerPaint());
    // if needed, draw a border for info window
    canvas.drawCircle(curScreenCoords.x, curScreenCoordsy, CIRCLE_RADIUS, getBorderPaint());
}

private Paint innerPaint, borderPaint;

public Paint getInnerPaint() {
    if (innerPaint == null) {
        innerPaint = new Paint();
        innerPaint.setARGB(225, 68, 89, 82); // gray
        innerPaint.setAntiAlias(true);
    }
    return innerPaint;
}

public Paint getBorderPaint() {
    if (borderPaint == null) {
        borderPaint = new Paint();
        borderPaint.setARGB(255, 68, 89, 82);
        borderPaint.setAntiAlias(true);
        borderPaint.setStyle(Style.STROKE);
        borderPaint.setStrokeWidth(2);
    }
    return borderPaint;
}

@Override
protected void onDraw(Canvas canvas) {
    Point p = new Point();
    for(OverlayItem item : items) {
        drawCircle(canvas, getProjection().toPixels(item.getPoint(), p));
    }
}