libgdx-scene2d-ui

libGDX Scene2D UI

Reference for Stage, Table layout, Skin, widgets, input handling, Actions system, coordinate conversion, and Viewport integration.

Stage

A scene graph that manages Actors, handles input events, and owns an internal SpriteBatch. In each frame you must call act(delta) then draw().

// In create() or show():
Stage stage = new Stage(new FitViewport(800, 480));
Gdx.input.setInputProcessor(stage);  // REQUIRED — without this, no UI input works

// In render():
ScreenUtils.clear(0.2f, 0.2f, 0.2f, 1f);
stage.act(Gdx.graphics.getDeltaTime());  // update Actions, fire pending events
stage.draw();                             // render all Actors

// In resize():
stage.getViewport().update(width, height, true);  // true = center camera

// In dispose():
stage.dispose();  // disposes internal SpriteBatch and all Actor resources

stage.act(delta) MUST be called before stage.draw(). act() advances Actions (animations, timers), processes pending events, and updates Actor state. Skipping it means Actions don't run and events don't fire.

Stage disposal: stage.dispose() disposes the Stage's SpriteBatch only when Stage created it (default constructor or Stage(viewport)). If you pass an external SpriteBatch via new Stage(viewport, batch), stage.dispose() does not dispose it — you must dispose that batch yourself. This matters when sharing a SpriteBatch between Stage and game rendering. Dispose Skin separately — Stage does not own it.

Actor

Base class for everything in the scene graph. Has position, size, rotation, origin, color, visibility, and name.

actor.setPosition(x, y);
actor.setSize(width, height);
actor.setRotation(degrees);     // counter-clockwise
actor.setColor(Color.RED);      // tints the actor
actor.setVisible(false);        // hides actor AND skips input
actor.setTouchable(Touchable.disabled);  // disables input, still visible
actor.addAction(action);        // attach an Action
actor.addListener(listener);    // attach an event listener