Getting Relative Coordinates from MotionEvent

Category: UI
Subcategory: Window/View Coordinates (X, Y)
Android Platform: 1.5, Google APIs 3
Referenced Classes: android.app.Activity, android.view.GestureDetector, android.view.GestureDetector.SimpleOnGestureListener, android.view.MotionEvent, android.view.View, android.view.Window, com.google.android.maps.GeoPoint, com.google.android.maps.MapView
Additional Info: Vertical Orientation

I wanted to place OverlayItems where long-press MotionEvents occurred. In order to determine the position of an OverlayItem, I needed to get the relative X and Y coordinates of the corresponding MotionEvent. As mentioned in the following forum (http://stackoverflow.com/questions/1410885/how-do-i-know-if-a-motionevent-is-relative-or-absolute), I was unable to obtain the relative X and Y coordinates using the methods MotionEvent.getX() and MotionEvent.getY(), respectively. Given that my MapView filled the entire screen, I came up with the following method:

code snippet
public static float[] getRelativeCoords(Activity activity, 
    MotionEvent e)
{
    // MapView
    View contentView= activity.getWindow().
        findViewById(Window.ID_ANDROID_CONTENT);
    return new float[] {
        e.getRawX() - contentView.getLeft(),
        e.getRawY() - contentView.getTop()};
}

Using GestureDetector and GestureDetector.SimpleOnGestureListener, and calling the above getRelativeCoords(...), I was able to place an OverlayItem where every long-press MotionEvent occurred:

code snippet
final MapView mapView= ...
final Activity mapViewActivity= this;

new GestureDetector(mapViewActivity, 
    new SimpleOnGestureListener()
{
    public void onLongPress(MotionEvent e)
    {
        float[] coords= getRelativeCoords(mapViewActivity, e);
        GeoPoint point= mapView.getProjection().fromPixels(
            (int) coords[0],
            (int) coords[1]);
        // create OverlayItem with point
        ...
        ...
    }
});