LibGDX FitViewport doesn't fit itself on construction, but it does on resize

Question

I'm racking my brain trying to figure out what's going on here... I'm using a FitViewport which is working great whenever I resize the screen, but when it's first created during the constructor it doesn't fit itself into the screen like it's supposed to (and like it does when I resize).

Here's the code for my constructor and for the resize() method:

public class UpgradesScreen implements Screen {

    private ScreenHandler sh;

    private OrthographicCamera cam;
    private Viewport viewport;

    public UpgradesScreen(ScreenHandler sh) {

        Gdx.app.log("UpgradesScreen", "Attached");

        this.sh = sh;

        cam = new OrthographicCamera();
        cam.setToOrtho(true, sh.V_WIDTH, sh.V_HEIGHT);

        viewport = new FitViewport(sh.V_WIDTH, sh.V_HEIGHT, cam);
        viewport.update(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());

    }

    @Override
    public void resize(int width, int height) {
        Gdx.app.log("UpgradesScreen", "resizing");
        viewport.update((int) width, (int) height);
    }

I've checked to make sure that Gdx.graphics.getWidth() gives the same figure as the 'width' argument the resize() method receives when I resize the screen (likewise with the 'height' values).

As far as I can tell the viewport should behave exactly the same during the constructor as it does when I resize. So why is it being stubborn and not updating to fit?

Here's what it looks like after I resize:

...and here's what it looks like when the screen is first created, before the window gets manually resized:

Answer 1

You are creating a new Viewport object which is not being used at all at start.

Call

viewport.apply();

Before your draw calls.

---

Also, resize method is called at start by default. Use it to initialize game objects in stead of constructor.

---

Edit:
Have a look at LibGDX Lifecycle.

resize is always called before render. There should not be different behavior at start and afterwards. That is your root problem. Try fixing it first.