BasicGameScreen.java

package com.example.util;

import com.example.ui.GameMenuModel;
import org.mini2Dx.core.Graphics;
import org.mini2Dx.core.Mdx;
import org.mini2Dx.core.assets.AssetManager;
import org.mini2Dx.core.game.GameContainer;
import org.mini2Dx.core.graphics.viewport.FitViewport;
import org.mini2Dx.core.graphics.viewport.Viewport;
import org.mini2Dx.core.screen.GameScreen;
import org.mini2Dx.core.screen.ScreenManager;
import org.mini2Dx.core.screen.transition.NullTransition;
import org.mini2Dx.ui.UiContainer;
import org.mini2Dx.ui.style.UiTheme;

public abstract class BasicGameScreen extends org.mini2Dx.core.screen.BasicGameScreen {
    protected final AssetManager assetManager;
    protected Viewport viewport;
    protected UiContainer uiContainer;
    protected int screenToLoad = -1;
    private UiModel view;


    protected BasicGameScreen(AssetManager assetManager) {
        this.assetManager = assetManager;
    }

    public <T extends UiModel> void initialise(GameContainer gc, Models model) {
        uiContainer = new UiContainer(gc, assetManager);
        InputMultiplexer
                .getInstance()
                .addProcessor(uiContainer);
        viewport = new FitViewport(true, gc.getWidth(), gc.getHeight());
        view = ScreenFactory.create(model, uiContainer);
        if (view != null) {
            uiContainer.add(view.getContainer());
        }
    }

    @Override
    public void update(GameContainer gc, ScreenManager<? extends GameScreen> screenManager, float delta) {
        if (!assetManager.update()) return;
        if (!UiContainer.isThemeApplied()) {
            UiContainer.setTheme(assetManager.get("ui/" + UiTheme.DEFAULT_THEME_FILENAME, UiTheme.class));
        }
        uiContainer.update(delta);
        getView().update(delta);
        if (screenToLoad != -1) {
            screenManager.enterGameScreen(screenToLoad, new NullTransition(), new NullTransition());
//            view.getContainer().setVisibility(Visibility.HIDDEN);
            screenToLoad = -1;
        }
        Mdx.input.setInputProcessor(uiContainer);
    }

    @Override
    public void render(GameContainer gc, Graphics g) {
        viewport.apply(g);
        uiContainer.render(g);
    }

    @Override
    public void onResize(int width, int height) {
        uiContainer.set(width, height);
    }

    protected <T extends UiModel> T getModel() {
        return (T) view;
    }
}

GameMenuModel.java

package com.example.ui;

import com.example.util.UiModel;
import org.mini2Dx.ui.UiContainer;
import org.mini2Dx.ui.annotation.UiElement;
import org.mini2Dx.ui.element.Container;

public class GameMenuModel extends UiModel {
    @UiElement(id = "GameMenu")
    Container container;

    @Override
    public Container getContainer() {
        return container;
    }

    @Override
    public void initialize(UiContainer uiContainer) {
        super.initialize(uiContainer);
    }
}

GameMenuScreen.java

package com.example.ui;

import com.example.util.BasicGameScreen;
import org.mini2Dx.core.assets.AssetManager;
import org.mini2Dx.core.game.GameContainer;

public class GameMenuScreen extends BasicGameScreen {
    public static final GameMenuModel model = GameMenuModel;
    public static final int ID = 1;


    public GameMenuScreen(AssetManager assetManager) {
        super(assetManager);
    }


    @Override
    public void initialise(GameContainer gc) {
        super.initialise(gc, model);
    }

    @Override
    public int getId() {
        return ID;
    }
}

ScreenFactory.md

Using the above pattern, you can implement a ScreenFactory using implemented api:

public static <T extends UiModel> T create(Models model, UiContainer uiContainer) {
        if (!isInitialized(uiContainer)) throw new MdxException("ScreenFactory not initialized!");

        if (isCached(model)) return (T) uiCache.get(model);

        if (model != null) {
            T container = (T) uiLoader.load(model.getLayout(), model.getInstance(), uiContainer);
            uiCache.put(model, container);

            Container modelContainer = container.getContainer();
            modelContainer.setWidthToWidthOf(uiContainer);
            modelContainer.setHeightToHeightOf(uiContainer);
            return container;
        }

        return null;
    }

UiModel.java

package com.example.util;

import org.mini2Dx.ui.UiContainer;
import org.mini2Dx.ui.element.Container;

public abstract class UiModel {

    public abstract Container getContainer();

    public void initialize(UiContainer uiContainer) {
        Container container = getContainer();
        container.setWidthToWidthOf(uiContainer);
        container.setHeightToHeightOf(uiContainer);
    }

    public void update(float delta) {
    }
}