android - 如何检测是否在 jBox2D 中触摸了特定的物体

Question

我正在开发一款使用 jbox2d 和 jBox2d for android 的游戏。我想检测用户是否触摸了我世界中各种物体中的特定动态物体。我试过遍历所有 body 并找到我感兴趣的一个，但它对我不起作用。请帮忙这是我所做的:

@Override
public boolean ccTouchesEnded(MotionEvent event)
{
    CGPoint location = CCDirector.sharedDirector().convertToGL(CGPoint.ccp(event.getX(), 
            event.getY()));

    for(Body b = _world.getBodyList();b.getType()==BodyType.DYNAMIC; b.getNext())
    {
        CCSprite sprite = (CCSprite)b.getUserData();
        if(sprite!=null && sprite instanceof CCSprite)
        {
            CGRect body_rect = sprite.getBoundingBox();
            if(body_rect.contains(location.x, location.y))
            {
                Log.i("body touched","<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<");
                expandAndStopBody(b);
                break;
            }

        }   
    }
return true;
}

触摸后，系统继续打印 GC_CONCURRENT freed 1649K, 14% free 11130K/12935K, paused 1ms+2ms and everything goes to hang like state.

Answer 1

要检查 body 是否被触摸，您可以使用世界对象的方法queryAABB。我尝试重新安排您的代码以使用该方法:

// to avoid creation every time you touch the screen
private QueryCallback qc=new QueryCallback() {

    @Override
    public boolean reportFixture(Fixture fixture) {
            if (fixture.getBody()!=null) 
            {
                    Body b=fixture.getBody();
                    CCSprite sprite = (CCSprite)b.getUserData();
                    Log.i("body touched","<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<");           
                    expandAndStopBody(b);
            }
            return false;
    }
};

private AABB aabb;

@Override
public boolean ccTouchesEnded(MotionEvent event)
{
    CGPoint location = CCDirector.sharedDirector().convertToGL(CGPoint.ccp(event.getX(), event.getY()));

    // define a bounding box with width and height of 0.4f
    aabb=new AABB(new Vec2(location.x-0.2f, location.y-0.2f),new Vec2(location.x+0.2f, location.y+0.2f));               
    _world.queryAABB(qc, aabb);            

    return true;
}

我尝试减少垃圾收集器，但必须实例化一些东西。有关 http://www.iforce2d.net/b2dtut/world-querying 的更多信息