Android (andengine + box2d) beginner - drag an object (sprite/body)

Question

I am currently following some tutorials to get introduced to andEngine and box2d and I would like to drag an object (sprite attached to body), whilst it is bouncing (it is registered to a physics world).

I would like to drag so I can see my character moving. It works only if I comment the code as below (the part where I am registering Physics connector). If I uncomment it, everything will work (e.g. even if I set other properties), except setPosition!! - I am sure the code is entering the ACTION_MOVE case

Question 1: why is this approach not working? - maybe I have to drag the body and not the sprite?

Question 2: how can I refer to the body and make operations in it WITHIN THE onAreaTouched? - I tried many different approaches, but it seams that you have to create the onAreaTouch when declaring the sprite only.

Reference: http://stuartmct.co.uk/2012/07/18/andengine-touch-events-with-sprites-and-shapes/ and AndEngine Book

Sprite sPlayer = new Sprite(CAMERA_WIDTH / 2, CAMERA_HEIGHT / 2,
                playerTextureRegion,
                this.mEngine.getVertexBufferObjectManager()) {
            @Override
            public boolean onAreaTouched(final TouchEvent pSceneTouchEvent,
                    final float pTouchAreaLocalX, final float pTouchAreaLocalY) {
                Log.i(this.getClass().getName(), "area touched");
                switch (pSceneTouchEvent.getAction()) {
                case TouchEvent.ACTION_DOWN:
                    break;
                case TouchEvent.ACTION_UP:
                    break;
                case TouchEvent.ACTION_MOVE:
                    this.setPosition(pSceneTouchEvent.getX() - this.getWidth()
                            / 2, pSceneTouchEvent.getY() - this.getHeight() / 2);
                    break;
                }

                return true;
            }
        };


        FixtureDef PLAYER_FIX = PhysicsFactory.createFixtureDef(10.0f, 0.75f,
                0.0f);
        // apply all forces, collisions to body - Dynamic
        Body body = PhysicsFactory.createCircleBody(physicsWorld, sPlayer,
                BodyType.DynamicBody, PLAYER_FIX);

The following code does not let me setPosition of Sprite:

/*
        // relate to collisions after adding to scene
        physicsWorld.registerPhysicsConnector(new PhysicsConnector(sPlayer,
                body, true, true));

*/

        this.scene.registerTouchArea(sPlayer);
        this.scene.setTouchAreaBindingOnActionDownEnabled(true);
        this.scene.attachChild(sPlayer);

user1762507 user1762507 · Accepted Answer · 2013-03-04T04:55:10

You will need to go

myPad.setTransform(pSceneTouchEvent.getX() - (this.getWidth() / 2), pSceneTouchEvent.getY() - (this.getHeight() / 2), 0);//the zero at the end is for setting the angle

Because with box2d you need to move the body and the physics connector

physicsWorld.registerPhysicsConnector(new PhysicsConnector(sPlayer, body, true, true));

will make the sprite follow the body.

Android (andengine + box2d) beginner - drag an object (sprite/body)

The following code does not let me setPosition of Sprite:

1 Answers