java - 在 Libgdx 中使用屏幕时重用代码

Question

根据我在阅读其他人关于如何制作不同屏幕的代码时的理解。你做一个主处理程序类......然后为每个屏幕创建一个新类。

让我感到困惑的是，每当你创建一个新屏幕时，你必须重新定义所有要渲染的东西，比如 SpriteBatch、 Sprite 、字体等。有没有办法在所有屏幕中重用这些东西？我的意思是，如果我有 10 个屏幕，并且希望能够在每个屏幕上绘制文本。为所有 10 个屏幕类创建一个新的 BitmapFont 真的是好的编程实践吗？

Answer 1

我创建了一个抽象屏幕类，其中包含屏幕的所有公共(public)对象，我的每个屏幕都扩展了这个抽象类。看起来像这样:

public abstract class AbstractScreen implements Screen {
    protected final Game game;

    protected InputMultiplexer multiInputProcessor;
    protected ScreenInputHandler screenInputHandler;

    protected Stage uiStage;
    protected Skin uiSkin;

    public AbstractScreen(Game game) {
        this.game = game;
        this.uiStage = new Stage();
        this.uiSkin = new Skin();

        this.screenInputHandler = new ScreenInputHandler(game);
        this.multiInputProcessor = new InputMultiplexer();

        multiInputProcessor.addProcessor(uiStage);
        multiInputProcessor.addProcessor(screenInputHandler);

        Gdx.input.setInputProcessor(multiInputProcessor);
    }

    private static NinePatch processNinePatchFile(String fname) {
        final Texture t = new Texture(Gdx.files.internal(fname));
        final int width = t.getWidth() - 2;
        final int height = t.getHeight() - 2;
        return new NinePatch(new TextureRegion(t, 1, 1, width, height), 3, 3, 3, 3);
    }

    @Override
    public void render (float delta) {
        Gdx.gl.glClearColor(0.2f, 0.2f, 0.2f, 1);
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        uiStage.act(Math.min(Gdx.graphics.getDeltaTime(), 1 / 30f));
        uiStage.draw();
        Table.drawDebug(uiStage);
    }

    @Override
    public void resize (int width, int height) {
    }

    @Override
    public void show() {
    }

    @Override
    public void hide() {
        dispose();
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public void dispose() {
        uiStage.dispose();
        uiSkin.dispose();
    }
}

当我想创建一个新类时，我只需扩展抽象屏幕并添加我需要的内容。例如，我有一个基本的信用屏幕，我只需要创建组件，但抽象屏幕会绘制它:

public class CreditsScreen extends AbstractScreen {

    public CreditsScreen(final Game game) {
        super(game);

        // Generate a 1x1 white texture and store it in the skin named "white".
        Pixmap pixmap = new Pixmap(1, 1, Format.RGBA8888);
        pixmap.setColor(Color.WHITE);
        pixmap.fill();
        uiSkin.add("white", new Texture(pixmap));

        // Store the default libgdx font under the name "default".
        BitmapFont buttonFont = new BitmapFont();
        buttonFont.scale(scale);
        uiSkin.add("default", buttonFont);

        // Configure a TextButtonStyle and name it "default". Skin resources are stored by type, so this doesn't overwrite the font.
        TextButtonStyle textButtonStyle = new TextButtonStyle();
        textButtonStyle.up = uiSkin.newDrawable("white", Color.DARK_GRAY);
        textButtonStyle.down = uiSkin.newDrawable("white", Color.DARK_GRAY);
        textButtonStyle.checked = uiSkin.newDrawable("white", Color.BLUE);
        textButtonStyle.over = uiSkin.newDrawable("white", Color.LIGHT_GRAY);
        textButtonStyle.font = uiSkin.getFont("default");
        uiSkin.add("default", textButtonStyle);

        // Create a table that fills the screen. Everything else will go inside this table.
        Table table = new Table();
        table.setFillParent(true);
        uiStage.addActor(table);

        table.debug(); // turn on all debug lines (table, cell, and widget)
        table.debugTable(); // turn on only table lines

        // Label
        BitmapFont labelFont = new BitmapFont();
        labelFont.scale(scale);
        LabelStyle labelStyle = new LabelStyle(labelFont, Color.BLUE);
        uiSkin.add("presents", labelStyle);
        final Label myName = new Label("Credits and all that stuff", uiSkin, "presents");

        table.add(myName).expand().center();
    }
}

我还有一个类可以处理所有屏幕的输入，具体目的是处理后退按钮在不同屏幕上的工作方式。并且这个输入处理程序类是在抽象类中创建的。

public class ScreenInputHandler implements InputProcessor {

    private final Game game;

    public ScreenInputHandler(Game game) {
        this.game = game;
    }

    @Override
    public boolean keyDown(int keycode) {
        if(keycode == Keys.BACK || keycode == Keys.BACKSPACE){       
            if (game.getScreen() instanceof MainMenuScreen) {
                Gdx.app.exit();
            }
            if (game.getScreen() instanceof GameScreen) {
                World.getInstance().togglePause(false);
            }
            if (game.getScreen() instanceof CreditsScreen) {
                game.setScreen(new MainMenuScreen(game));
            }
        }
        return false;
    }

}