Libgdx Touchpad Knob Won't Resize Properly

Question

I'm making a game for android in libgdx and I have been working on implementing a viewport. I have a libgdx touchpad as an actor on the stage and as soon as I apply the FitViewport to the stage, the touchpad knob does not resize correctly and fills the screen while all of the other elements resize properly. How do I get the touchpad knob to resize along with the other elements?

Here is my code:

private Touchpad touchpad;
private Touchpad.TouchpadStyle touchpadStyle;
private Skin touchpadSkin;
private Drawable touchBackground;
private Drawable touchKnob;

public PlayState(GameStateManager gsm) {
    super(gsm);
    touchpadSkin = new Skin();
    //Set background image
    touchpadSkin.add("touchBackground", new Texture("joystick_base.png")); 
    //Set knob image
    touchpadSkin.add("touchKnob", new Texture("joystick_64.png"));
    //Create TouchPad Style
    touchpadStyle = new Touchpad.TouchpadStyle();
    //Create Drawable's from TouchPad skin
    touchBackground = touchpadSkin.getDrawable("touchBackground");
    touchKnob = touchpadSkin.getDrawable("touchKnob");
    touchpadStyle.background = touchBackground;
    touchpadStyle.knob = touchKnob;

    //Create new TouchPad with the created style
    touchpad = new Touchpad(10, touchpadStyle);
    //setBounds(x,y,width,height)
    touchpad.setBounds(0.5f,0.5f,WORLD_WIDTH/7,WORLD_HEIGHT/5);


    stage = new Stage(new FitViewport(WORLD_WIDTH,WORLD_HEIGHT));
    stage.addActor(touchpad);
    Gdx.input.setInputProcessor(stage);

protected void render(SpriteBatch sb) {
    touchpad.draw(sb, 1);
}

Answer 1

Try to update viewport on resize method:

 stage.getViewport().update(width, higth);