Framerate independent movement speed

[patrikturi]

1. Moving a sprite
   This doesn't work:

public class PlayState extends FlxState ...
@Override
public void update() {
    sprite.x += FlxG.elapsed*60;
}

because FlxG.elapsed is just a constant, not the actual elapsed time.
This doesn't produce the same speed either in my test:

sprite.x += Gdx.graphics.getDeltaTime()*60;

2. Box2D physics
   When I'm using Box2D and have a state extending B2FlxState, in the update method I call super.update() and the physics also slows down when framerate drops. B2FlxState's update method has the same problem:

_frameTime = FlxG.elapsed;

3. Side question: how to measure actual FPS?

[moly]

Have you tried getting the delta time like this:

private long prevTime;

@Override
public void create()
{
    prevTime = System.currentTimeMillis();
}

@Override
public void update()
{
     long time = System.currentTimeMillis();
     long delta = time - prevTime;

     prevTime = time;
}

[patrikturi]

Thank you, your suggestion works. Now only the following things remain:
a) B2FlxState.update() shall use this delta time calculated above instead of FlxG.elapsed:

public void update()
{
    _frameTime = FlxG.elapsed;
    _stepsPerformed = 0;
    while((_frameTime > 0.0) && (_stepsPerformed < MAXIMUM_NUMBER_OF_STEPS))
    {
        _deltaTime = FlxU.min(_frameTime, FIXED_TIMESTEP);
        _frameTime -= _deltaTime;
    ...

Because FlxG.elapsed is just a constant not the actual delta time. (I can write some workaround code when calling B2FlxState.update() for now but it should be fixed.)
b) I think it would be good to have this delta time available in FlxG.
edit: I've tried sprite.velocity.x = 30; and it is also not framerate independent.