libgdx 2D 粒子效果

先贴几个文档链接：

https://github.com/libgdx/libgdx/wiki/2d-particle-effects

https://github.com/libgdx/libgdx/wiki/2D-Particle-Editor

http://www.java-gaming.org/topics/particle-effects-in-libgdx/29484/view.html

先贴个官网GitHub上的测试代码，代码和资源都可以去下。这里不能传附件？？

public class ParticleEmitterTest extends GdxTest {
    private SpriteBatch spriteBatch;
    ParticleEffect effect;
    int emitterIndex;
    Array<ParticleEmitter> emitters;
    int particleCount = 10;
    float fpsCounter;
    InputProcessor inputProcessor;

    @Override
    public void create () {
        spriteBatch = new SpriteBatch();

        effect = new ParticleEffect();
        effect.load(Gdx.files.internal("data/test.p"), Gdx.files.internal("data"));//第一个参数是粒子效果文件，第二个参数是图片basepath
        effect.setPosition(Gdx.graphics.getWidth() / 2, Gdx.graphics.getHeight() / 2);
        // Of course, a ParticleEffect is normally just used, without messing around with its emitters.
        emitters = new Array(effect.getEmitters());//原笔者把多个效果都放在一个文件里了，为了显示需要，这里特殊处理了，如果注释掉这三行，可以看出，几个效果一起显示了
        effect.getEmitters().clear();
        effect.getEmitters().add(emitters.get(0));

        inputProcessor = new InputProcessor() {
            public boolean touchUp (int x, int y, int pointer, int button) {
                return false;
            }

            public boolean touchDragged (int x, int y, int pointer) {
                effect.setPosition(x, Gdx.graphics.getHeight() - y);
                return false;
            }

            public boolean touchDown (int x, int y, int pointer, int newParam) {//改变粒子的个数，重新显示
                // effect.setPosition(x, Gdx.graphics.getHeight() - y);
                ParticleEmitter emitter = emitters.get(emitterIndex);
                particleCount += 100;
                System.out.println(particleCount);
                particleCount = Math.max(0, particleCount);
                if (particleCount > emitter.getMaxParticleCount()) emitter.setMaxParticleCount(particleCount * 2);
                emitter.getEmission().setHigh(particleCount / emitter.getLife().getHighMax() * 1000);
                effect.getEmitters().clear();
                effect.getEmitters().add(emitter);
                return false;
            }

            public boolean keyUp (int keycode) {
                return false;
            }

            public boolean keyTyped (char character) {
                return false;
            }

            public boolean keyDown (int keycode) {
                ParticleEmitter emitter = emitters.get(emitterIndex);
                if (keycode == Input.Keys.W)//我没找到原始的键，我改成W
                    particleCount += 5;
                else if (keycode == Input.Keys.S)////我没找到原始的键，我改成S
                    particleCount -= 5;
                else if (keycode == Input.Keys.SPACE) {
                    emitterIndex = (emitterIndex + 1) % emitters.size;
                    emitter = emitters.get(emitterIndex);

                    // if we've previously stopped the emitter reset it
                    if (emitter.isComplete()) emitter.reset();
                    particleCount = (int)(emitter.getEmission().getHighMax() * emitter.getLife().getHighMax() / 1000f);
                } else if (keycode == Input.Keys.ENTER) {
                    emitter = emitters.get(emitterIndex);
                    if (emitter.isComplete())
                        emitter.reset();
                    else
                        emitter.allowCompletion();
                } else
                    return false;
                particleCount = Math.max(0, particleCount);
                if (particleCount > emitter.getMaxParticleCount()) emitter.setMaxParticleCount(particleCount * 2);
                emitter.getEmission().setHigh(particleCount / emitter.getLife().getHighMax() * 1000);
                effect.getEmitters().clear();
                effect.getEmitters().add(emitter);
                return false;
            }

            @Override
            public boolean mouseMoved (int x, int y) {
                return false;
            }

            @Override
            public boolean scrolled (int amount) {
                return false;
            }
        };

        Gdx.input.setInputProcessor(inputProcessor);
    }

    @Override
    public void dispose () {
        spriteBatch.dispose();
        effect.dispose();//注意
    }

    public void render () {
        spriteBatch.getProjectionMatrix().setToOrtho2D(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
        float delta = Gdx.graphics.getDeltaTime();
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        spriteBatch.begin();
        effect.draw(spriteBatch, delta);//这里绘制粒子效果
        spriteBatch.end();
        fpsCounter += delta;
        if (fpsCounter > 3) {
            fpsCounter = 0;
            int activeCount = emitters.get(emitterIndex).getActiveCount();
            Gdx.app.log("libgdx", activeCount + "/" + particleCount + " particles, FPS: " + Gdx.graphics.getFramesPerSecond());
        }
    }

    public boolean needsGL20 () {
        return false;
    }
}

这只是测试代码，我们平时在使用的时候，几乎不这么用。

1. 大多数情况下我们都是用stage/actor结构的，不会在Screen里专门去draw粒子效果，或者说是很少情况下。

2. 效果文件在使用的时候大多数都是调好了的，不需要我们代码去调节那些参数。

3. ParticleEffectPool我还没看呢....

好，我们先在stage中尝试绘制一个粒子效果

其实只是自定义包装一个Actor类，在draw的时候，draw里面的effect就好了。

见代码：

public class ParticleEffectActor extends Actor {
    ParticleEffect particleEffect;
    Vector2 acc = new Vector2();
    private static final Logger LOGGER = new Logger(ParticleEffectActor.class.getName(), Application.LOG_DEBUG);
    public ParticleEffectActor(ParticleEffect particleEffect) {
        super();
        this.particleEffect = particleEffect;
    }

    @Override
    public void draw(Batch batch, float parentAlpha) {
        particleEffect.draw(batch);
        //LOGGER.debug("draw");
    }

    @Override
    public void act(float delta) {
        super.act(delta);
        acc.set(getWidth() / 2, getHeight() / 2);
        localToStageCoordinates(acc);
        //LOGGER.debug(acc.toString());
        particleEffect.setPosition(acc.x, acc.y);
        particleEffect.update(delta);

    }

    public void start(){
        particleEffect.start();
    }
}

public class ParticleTest extends ApplicationAdapter implements InputProcessor {
    private Stage stage;
    private ParticleEffect effect;
    private static final Logger LOGGER = new Logger(ParticleTest.class.getName(),Application.LOG_DEBUG);
    
    @Override
    public void create () {
        Gdx.app.setLogLevel(Application.LOG_DEBUG);
        stage = new Stage();
        Gdx.input.setInputProcessor(this);
        effect = new ParticleEffect();
        effect.load(Gdx.files.internal("data/abc.p"), Gdx.files.internal("data"));//第一个参数是粒子效果文件，第二个参数是图片basepath(这里应该有一个默认的particle.png别忘了)

    }

    @Override
    public void render () {
        Gdx.gl.glClearColor(0.2f, 0.2f, 0.2f, 1);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        stage.act();
        stage.draw();
    }

    @Override
    public void dispose() {
        effect.dispose();
        stage.dispose();
        super.dispose();
    }

    @Override
    public void resize(int width, int height) {
        stage.getViewport().update(width,height);
        super.resize(width, height);
    }

    private void addEffect(){
        final ParticleEffectActor actor = new ParticleEffectActor(effect);

        actor.setPosition(0,0);

        MoveToAction action = Actions.moveTo(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), 4.0f);

        RunnableAction run = Actions.run(new Runnable() {
            @Override
            public void run() {
                stage.getActors().removeValue(actor, true);
            }
        });
        actor.addAction(Actions.sequence(action,run));
        actor.start();
        stage.addActor(actor);
    }

    @Override
    public boolean keyDown(int keycode) {
        if(keycode == Input.Keys.J){
            addEffect();
        }
        return false;
    }

    @Override
    public boolean keyUp(int keycode) {
        return false;
    }

    @Override
    public boolean keyTyped(char character) {
        return false;
    }

    @Override
    public boolean touchDown(int screenX, int screenY, int pointer, int button) {
        return false;
    }

    @Override
    public boolean touchUp(int screenX, int screenY, int pointer, int button) {
        return false;
    }

    @Override
    public boolean touchDragged(int screenX, int screenY, int pointer) {
        return false;
    }

    @Override
    public boolean mouseMoved(int screenX, int screenY) {
        return false;
    }

    @Override
    public boolean scrolled(int amount) {
        return false;
    }
}

以上代码中，我们在按下J键的时候，在stage中添加一个粒子效果actor，这个actor从左下角开始向右上角移动，4秒。

注意actor的start方法，官方粒子的素材不需要就可以显示，如果是粒子编辑器默认例子没改过，则需要这个。可能跟life什么的设置有关吧。

至于快速连续按下J键看到的情况，还有待研究，可能是共用同一个effect的缘故,particleEffect的update每个都调用了。

那倒不如把particleEffect直接放到actor中去构造，释放也放在里面，待研究吧。