AndEngine和Box2D中的弹簧墙

Question

I use Box2D in my game, but I would like to have a nicely looking spring - wall to push the player when touched. It would look like this (in 3 frames):

Question: how to implement it? Can I attach a wall effect to an animated sprite?

Answer 1

The answer is: Prismatic Joint. I divided the image into 2 parts: static and dynamic (the moving bar). The below code is for creation of a prismatic joint in orientation like in the image in my question:

//prismatic joint
    final Sprite springFrameT = new Sprite(pX, pY, mSpringFrameTRegion, getVertexBufferObjectManager());
    final Sprite springBarT = new Sprite(pX, pY + mSpringFrameTRegion.getHeight()-mSpringBarTRegion.getHeight(), 
            mSpringBarTRegion, getVertexBufferObjectManager());        
    mMainScene.attachChild(springFrameT);
    mMainScene.attachChild(springBarT);        
    mMapSprites.add(springFrameT);
    mMapSprites.add(springBarT);

    final Body springFrameBody = PhysicsFactory.createBoxBody(mPhysicsWorld, springFrameT, BodyType.StaticBody, FIXTURE_DEF);
    final Body springBarBody = PhysicsFactory.createBoxBody(mPhysicsWorld, springBarT, BodyType.DynamicBody, SPRING_FIXTURE_DEF);        
    mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(springFrameT, springFrameBody, false, false));
    mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(springBarT, springBarBody, true, true));

    final PrismaticJointDef prismaticJointDef = new PrismaticJointDef();        
    prismaticJointDef.initialize(springFrameBody, springBarBody, springFrameBody.getWorldCenter(), // new Vector2(springFrameT.getWidth(), springFrameT.getHeight()/2), 
            new Vector2(0, 1.0f)); 
    prismaticJointDef.lowerTranslation = -0.5f;
    prismaticJointDef.upperTranslation = 0.5f;
    prismaticJointDef.enableLimit = true;
    prismaticJointDef.enableMotor = true;
    prismaticJointDef.maxMotorForce = 100.0f;
    prismaticJointDef.motorSpeed = 100000f;
    prismaticJointDef.collideConnected = false;
    this.mPhysicsWorld.createJoint(prismaticJointDef);