碰撞后如何使两个身体粘住？ [英] How to make two bodies stick after a collision?

问题描述

我真的坚持这个我可以成功检测到碰撞，但是我无法让碰撞中的两个物体粘在一起。

I am really stuck on this I can successfully detect a collision but I can't make the two bodies involved in the collision to stick.

这是我的 ContactListener

world.setContactListener(listener);

    listener = new ContactListener() {

        @Override
        public void preSolve(Contact contact, Manifold oldManifold) {

        }


        @Override
        public void postSolve(Contact contact, ContactImpulse impulse) {

        }

        //called when two fixtures cease to touch
        @Override
        public void endContact(Contact contact) {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("beginContact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }

        //called when two fixtures begin to touch
        @Override
        public void beginContact(Contact contact) {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("beginContact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }
    };

这也是我在world.step（）行之后直接放在我的render（）中的内容/ p>

Also this is what I put in my render() straight after the world.step() line

int numContacts = world.getContactCount();

    if(numContacts > 0)
    {
        Gdx.app.log("contact", "start of contact list");
        for(Contact contact: world.getContactList())
        {
            Fixture fixtureA = contact.getFixtureA();
            Fixture fixtureB = contact.getFixtureB();
            Gdx.app.log("contact", "between" + fixtureA.toString() + "and" + fixtureB.toString());
        }
        Gdx.app.log("contact", "end of contact list");
    }

我非常坚持在解决问题或预先解决的问题上困惑。我按照iforce2d粘性射弹 http://www.iforce2d.net/b2dtut/sticky-projectiles但是我不懂C ++，在eclipse中工作时会遇到很多语法错误。请有人给我看一个工作碰撞的示例代码，在java中碰撞后机体粘在一起。

I am extremely stuck on what to put on post solve or pre-solve really confused. I followed the iforce2d sticky projectiles http://www.iforce2d.net/b2dtut/sticky-projectiles but I don't understand C++ and i get a lot of syntax errors when working in eclipse. Please can someone show me an example code of a working collision where bodies stick together after colliding in java please.

推荐答案

这是怎么回事你创建了一个 WeldJoint 使用libgdx包装器：

This is how you create a WeldJoint with the libgdx wrapper:

WeldJointDef wd = new WeldJointDef();
wd.bodyA = body1;
wd.bodyB = body2;
wd.referenceAngle = wd.bodyB.getAngle() - wd.bodyA.getAngle();
world.createJoint( wd );

不要尝试在ContactListener中创建Joints。将要粘贴的实体添加到列表中，然后在 world.step 之后检查它们。

Do not try to create Joints inside the ContactListener. Add the bodies to be glued to a list and check them just after world.step.

编辑：

好的，就像 iforce2d教程，创建一个包含2个实体的对象：

Ok, like in the iforce2d tutorial,create an object to contain 2 bodies:

public class StickyInfo{
    Body bodyA;
    Body bodyB;
    public StickyInfo(Body bodyA, Body bodyB){
        this.bodyA = bodyA;
        this.bodyB = bodyB;
    }
};

然后创建 libgdx数组

Array<StickyInfo> collisionsToMakeSticky = new Array<StickyInfo>();

当身体碰撞时（好吧，技术上他们的固定装置），将它们添加到此列表中：

When the bodies collide (well, technically their fixtures), add them to this list:

collisionsToMakeSticky.add(new StickyInfo(body1, body2))

然后在 world.step 之后，如果数组不为空。创建WeldJoints：

And then just after world.step, if the Array is not empty. Create the WeldJoints:

while(collisionsToMakeSticky.size>0){
    StickyInfo si = collisionsToMakeSticky.removeIndex(0);
    //Make the WeldJoint with the bodies si.bodyA and si.bodyB
}

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