TestMenu.java

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.GL10;
import com.badlogic.gdx.scenes.scene2d.InputEvent;
import com.badlogic.gdx.scenes.scene2d.Stage;
import com.badlogic.gdx.scenes.scene2d.ui.Skin;
import com.badlogic.gdx.scenes.scene2d.ui.Table;
import com.badlogic.gdx.scenes.scene2d.ui.TextButton;
import com.badlogic.gdx.scenes.scene2d.utils.ClickListener;


public class TestMenu implements ApplicationListener, GameContext {

	public interface ButtonListener {
		public void clicked(GameContext context);
	}
	
	public enum ButtonActions implements ButtonListener {
		
		PLAY("Play Game") {
			@Override
			public void clicked(GameContext context) {
				context.enterGame();
			}
		},
		
		EXIT("Exit") {
			@Override
			public void clicked(GameContext context) {
				context.exit();
			}
		};
		
		public final String text;
		
		ButtonActions(String text) {
			this.text = text;
		}
	}
	
	Stage stage;
	Skin skin;
	Table menuRoot;
	
	@Override
	public void create() {
		//set up a new stage
		stage = new Stage();
		
		// Requires the following skin/font files to be placed in "assets/data" 
		// of your Android project
		//https://raw.github.com/libgdx/libgdx/master/tests/gdx-tests-android/assets/data/uiskin.json
		//https://raw.github.com/libgdx/libgdx/master/tests/gdx-tests-android/assets/data/uiskin.atlas
		//https://raw.github.com/libgdx/libgdx/master/tests/gdx-tests-android/assets/data/uiskin.png
		//https://raw.github.com/libgdx/libgdx/master/tests/gdx-tests-android/assets/data/default.fnt
		//https://raw.github.com/libgdx/libgdx/master/tests/gdx-tests-android/assets/data/default.png
		
		// Presumably your game would use a custom GUI skin eventually ...
		
		//create a basic GUI skin 
		skin = new Skin(Gdx.files.internal("data/uiskin.json"));
		
		//make sure input goes through our stage
		Gdx.input.setInputProcessor(stage);
		
		//initialize our menu GUI
		setupGUI();
		
		//load the menu state
		enterMenu();
	}
	
	public void setupGUI() {
		//let's say your game implements GameContext
		final GameContext context = this;
		
		//the "root" container; which fills the screen
		menuRoot = new Table(skin);
		menuRoot.setFillParent(true);
		
		Table table = new Table(skin);
		
		//add each button to the menu
		final int BUTTON_WIDTH = 100;
		for (final ButtonActions a : ButtonActions.values()) {
			//create a new text button.. we could use ImageButton instead
			TextButton btn = new TextButton(a.text, skin);
			//add a listener
			btn.addListener(new ClickListener() {
				public void clicked(InputEvent e, float x, float y) {
					a.clicked(context);
				}
			});
			//add the button with a fixed width
			table.add(btn).width(BUTTON_WIDTH);
			//then move down a row
			table.row();
		}
		//ad the button group to the root
		menuRoot.add(table);
	}

	@Override
	public void resize(int width, int height) {
		//resize the stage to the new window size
		stage.setViewport(width, height, false);
	}

	@Override
	public void render() {
		//clear the screen
		Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
		
		//update and draw the stage UI
		stage.act();
		stage.draw();
	}

	@Override
	public void pause() {
		
	}

	@Override
	public void resume() {
		
	}

	@Override
	public void dispose() {
		
	}
	
	//gameContext interface methods...

	@Override
	public void exit() {
		Gdx.app.exit();
	}

	@Override
	public void enterGame() {
		//clears the stage and adds the game GUI
		stage.clear();
		//TODO: add game actors...
	}

	@Override
	public void enterMenu() {
		//clears the stage and adds the menu GUI
		stage.clear();
		stage.addActor(menuRoot);
	}
}