libgdx - how to add background image in stage?

问题

I am learning libgdx but i am stuck at a point..

I have added a button in my stage , now i want to add a image in the stage so that the image looks as the background image to the button.i mean to say that the button should lie on the image. I have been looking tutorials but not been able to do that.

How can it be done? any help?

回答1:

The only thing you need to do is to draw the background, before drawing the Buttons.
There are a few possible ways to do that:
- You can add the background as an Image (subclass of Actor) to the Stage and use the z-index to make sure it is drawn as a background.
- You can get the Stages SpriteBatch (stage.getBatch()) and use one of its draw methods to draw the background, before calling stage.draw()

You could also use another SpriteBatch, but i don't recommend it, as it is a pretty "heavy" object and it is just not neccessaty in this case.
I guess, before calling stage.draw() you need to call spritebatch.end(), for the SpriteBatch you used to draw the background.

回答2:

A small example :

stage.act(Gdx.graphics.getDeltaTime());

stage.getBatch().begin();
stage.getBatch().draw(background, 0, 0, WORLD_WIDTH, WORLD_HEIGHT);
stage.getBatch().end();

stage.draw();

回答3:

Here is some code I used to mimic a health bar. I used a ProgressBar.

    stage = new Stage();
    Texture bground = new Texture(Gdx.files.internal("pbBackground.png"));
    Table table = new Table();
    table.setFillParent(true);
    stage.addActor(table);
    font = new BitmapFont(Gdx.files.internal("gamefonts.fnt"));
    font.getData().scale(.1f);
    skin = new Skin();
    pixmap = new Pixmap(1, 1, Format.RGBA8888);
    pixmap.setColor(Color.WHITE);
    pixmap.fill();
    skin.add("white", new Texture(pixmap));
    LabelStyle lstyle = new LabelStyle();
    lstyle.font=font;
    Label mylabel = new Label("HP", lstyle);
    mylabel.setColor(Color.RED);
    mylabel.setPosition(1, 6);
    table.addActor(mylabel);
    textureBar = new TextureRegionDrawable(new TextureRegion(new Texture(Gdx.files.internal("pb.png"))));
    barStyle = new ProgressBarStyle(skin.newDrawable("white", Color.DARK_GRAY), textureBar);
    barStyle.background = new TextureRegionDrawable(new TextureRegion(bground));
    barStyle.knobBefore=barStyle.knob;
    bar = new ProgressBar(0, 10, 0.5f, false, barStyle);
    bar.setPosition(1, 1);
    bar.setValue(0);
    bar.setAnimateDuration(2);
    table.addActor(bar);

This website may help you understand progressbars better. Also look at the docs for ProgressBar.

来源：https://stackoverflow.com/questions/22536755/libgdx-how-to-add-background-image-in-stage