why getSpeed() always return 0 on android

Question

I need to get the speed and heading from the gps. However the only number i have from location.getSpeed() is 0 or sometimes not available. my code:

Answer 1

Based on other suggestions here I put together this code with comments to why:

public static float getSpeedKmh(Location newLocation, Location previousLocation)
{
    if(newLocation == null) throw new IllegalArgumentException("newLocation must not be null");
    float speed = -1.0f;
    if(newLocation.hasSpeed()) /* gps doppler speed at the current moment preferred */
    {
        speed = newLocation.getSpeed();
    }else /* may be wifi or celltower based location: compute AVERAGE speed since last fix */
    {
       if(previousLocation == null) throw new IllegalArgumentException("Cannot compute speed without previousLocation (was null)");
       if(previousLocation.getTime()==newLocation.getTime())
           throw new IllegalArgumentException("Cannot compute speed from same time locations!"); /* diff by zero protection */
       speed = newLocation.distanceTo(previousLocation) * 1000.0f /* time diff in millis so multiply by 1000 */
           / Math.abs(newLocation.getTime() - previousLocation.getTime()); /* Math abs: so you can even swap new and older location without effect */
    }
       return speed * 3.6f; /* m/s -> km/h */
}