在 box2d 和engine 中设置启用的联系人

Question

如何在 box2d (Andengine) 中禁用两个物体之间的接触。我已经使用了 contact.setEnabled(false) 但这对我不起作用。我在下面给出了代码供参考。

    @Override
    public void beginContact(final Contact pContact) 
    {
        final Fixture fixtureA = pContact.getFixtureA();
        final Body bodyA = fixtureA.getBody();
        final Object userDataA = bodyA.getUserData();

        final Fixture fixtureB = pContact.getFixtureB();
        final Body bodyB = fixtureB.getBody();
        final Object userDataB = bodyB.getUserData();


        if(userDataA==null || userDataB==null)
            return;


        if(userDataA.equals(target) && userDataB.equals(ball)
        {   
              pContact.setEnabled(false);             

            }               
    }

Answer 1

    @Override
    public void preSolve(Contact contact, Manifold oldManifold)
    {
        PhysicsConnectorManager mPC =     this.mPhysicsWorld.getPhysicsConnectorManager();
        Body targetBody = mPC.findBodyByShape(target);
        Body ballBody = mPC.findBodyByShape(ball);
        if (contact.getFixtureA().getBody() == targetBody && contact.getFixtureB().getBody() == ballBody)
        {
            contact.setEnabled(false);
        }
        else
        {
            contact.setEnabled(true);
        }
    }

Answer 2

就 Box2D 而言，您的代码看起来基本上是正确的，除此之外，您还需要检查球和目标是否相反：

if( (userDataA.equals(target) && userDataB.equals(ball)) || 
    (userDataB.equals(target) && userDataA.equals(ball)) )

但我认为您的主要问题可能是使用final...为什么final ？我不是java专家，但它看起来非常可疑，快速浏览一下维基百科就会说：“最终变量只能初始化一次”。要保持接触禁用，您需要每帧执行 SetEnabled(false) 操作。

Answer 3

我遇到了同样的问题，感谢@Rooban 和他的评论“fixture.isSensor=true;”我解决了。我正在使用 box2dweb （JavaScript 端口），因为所有 box2d API 都很相似，这可能会对您有所帮助。

假设您有两个物体，一堵墙和一个玩具。玩具正在穿过墙壁。

    //WALL (toy detector)

    var toyDetectorFixDef = new box2d.b2FixtureDef();
    toyDetectorFixDef.density = 1;
    toyDetectorFixDef.friction = 0.5;
    toyDetectorFixDef.restitution = 0.5;
    toyDetectorFixDef.shape = new box2d.b2PolygonShape;
    toyDetectorFixDef.shape.SetAsBox(80 / SCALE, 5 / SCALE);//, new box2d.b2Vec2(bodyDef3.x, bodyDef3.y ), 4);

    //BE SURE YOU ADDED THIS LINE, SO THIS OBJECT IS ACTING AS A SENSOR
    toyDetectorFixDef.isSensor = true;

    var toyDetectorBodyDef = new box2d.b2BodyDef();
    toyDetectorBodyDef.type = box2d.b2Body.b2_staticBody;
    toyDetectorBodyDef.position.x = 100 / SCALE;
    toyDetectorBodyDef.position.y = 280 / SCALE;

    var rbDataToyDetector = new Object();
    rbDataToyDetector.bodyType = "toyDetector";
    toyDetectorBodyDef.userData = rbDataToyDetector;

    var toyDetectorBox = world.CreateBody(toyDetectorBodyDef);
    toyDetectorBox.CreateFixture(toyDetectorFixDef);

然后你必须添加 TOY 对象。

    //TOY object

    var fixDef = new box2d.b2FixtureDef();
    fixDef.density = 1;
    fixDef.friction = 0.5;
    fixDef.restitution = 0.5;
    bodyDef = new box2d.b2BodyDef();
    bodyDef.type = box2d.b2Body.b2_dynamicBody;
    bodyDef.position.x = 200 / SCALE + Math.random() * 400 / SCALE;
    bodyDef.position.y = 0;
    var rbDataBall = new Object();
    rbDataBall.bodyType = "toy";
    bodyDef.userData = rbDataBall;
    fixDef.shape = new box2d.b2CircleShape(20 / SCALE);


    var toyBox = world.CreateBody(bodyDef);
    toyBox.CreateFixture(fixDef);

现在，当您拥有对象时，您必须检查碰撞情况。

        try {
        var listener = new Box2D.Dynamics.b2ContactListener;
        listener.BeginContact = function (contact) {

            if ((contact.GetFixtureA().GetBody().GetUserData().bodyType == "toyDetector" && contact.GetFixtureB().GetBody().GetUserData().bodyType == "toy") ||
                    (contact.GetFixtureA().GetBody().GetUserData().bodyType == "toy" && contact.GetFixtureB().GetBody().GetUserData().bodyType == "toyDetector")) {

                //YOUR CODE HERE
                console.log("Toy detected!");

            }

        }

        world.SetContactListener(listener);
    }
    catch (e) {
        console.log(e.toString());
    }

我希望这会对您有所帮助。