Problem with Widget Event Reporting in Libgdx

Question

So I'm trying to test an ImageButton on an Android device. I can get the button to appear on the screen, but when I press it nothing happens or appears on the log. Here is what I have in the Show() method of a class that implements the Screen class.

public void show() {
    uistage = new Stage();
    Texture tankSprite = new Texture(Gdx.files.internal("TankSpriteBase.png"));     
    tank = new Tank(0, true, tankSprite);
    tank.rect.x = 100;
    tank.rect.y = 100;
    tank.rect.width = 44;
    tank.rect.height = 45;

    dropSound = Gdx.audio.newSound(Gdx.files.internal("drop.wav"));
    rainMusic = Gdx.audio.newMusic(Gdx.files.internal("rain.mp3"));

    rainMusic.setLooping(true);
    rainMusic.play();

    float w = 800;
    float h = 400;

    camera = new OrthographicCamera();
    camera.setToOrtho(false, w, h);
    batch = new SpriteBatch();
ImageButton.ImageButtonStyle ibs = new ImageButton.ImageButtonStyle();
    ibs.up = new TextureRegionDrawable(
                new TextureRegion(
                        new Texture(Gdx.files.internal("direction_left.png"))));
    ibs.down = new TextureRegionDrawable(
                new TextureRegion(
                        new Texture(Gdx.files.internal("direction_left_pressed.png"))));

    leftButton = new ImageButton(ibs);
    leftButton.setX(300);
    leftButton.setY(300);
    leftButton.addListener(new InputListener() {
        public boolean touchDown (InputEvent event, float x, float y, int pointer, int button) {
                Gdx.app.log(LOG, "down");
                System.out.println("down");
                return true;
        }

        public void touchUp (InputEvent event, float x, float y, int pointer, int button) {
                Gdx.app.log(LOG, "up");
                System.out.println("up");
        }
    });
    leftButton.setWidth(ibs.up.getMinWidth());
    leftButton.setHeight(ibs.up.getMinHeight());
    leftButton.setBounds(0, 0, ibs.up.getMinWidth(), ibs.up.getMinHeight());
    leftButton.setTouchable(Touchable.enabled);

    uistage.addActor(leftButton);
            Gdx.app.log(LOG, "Width is "+Gdx.graphics.getWidth()+" and height is "+Gdx.graphics.getHeight());

    background = new Texture(Gdx.files.internal("background.png"));
    background.setFilter(TextureFilter.Linear, TextureFilter.Linear);

    TextureRegion region = new TextureRegion(background, 0, 0, 512, 301);

    sprite = new Sprite(region);
    sprite.setSize(0.9f, 0.9f * sprite.getHeight() / sprite.getWidth());
    sprite.setOrigin(sprite.getWidth()/2, sprite.getHeight()/2);
    sprite.setPosition(-sprite.getWidth()/2, -sprite.getHeight()/2);
            }

Might anyone know why this doesn't appear to be working?

Answer 1

Oh wow, completely bungled this. I forgot to add:

Gdx.input.setInputProcessor(uistage);

Why this is important is detailed here. Remember to check your code and read your docs, kids! (Eat your veggies too)