Question

I am using this method in Andengine to scroll through a list of items, by setting the camera’s offset.

@Override
        public void onScroll(ScrollDetector pScollDetector, int pPointerID,
                float pDistanceX, float pDistanceY) {
            //Disable the menu arrows left and right (15px padding)
            if(mCamera.getXMin()<=15)
                menuleft.setVisible(false);
             else
                menuleft.setVisible(true);

             if(mCamera.getXMin()>mMaxX-15)
                 menuright.setVisible(false);
             else
                 menuright.setVisible(true);

            //Return if ends are reached
            if ( ((mCurrentX - pDistanceX) < mMinX)  ){                 
                return;
            }else if((mCurrentX - pDistanceX) > mMaxX){

                return;
            }

            //Center camera to the current point
            this.mCamera.offsetCenter(-pDistanceX,0 );
            mCurrentX -= pDistanceX;


            //Set the scrollbar with the camera
            float tempX =mCamera.getCenterX()-CAMERA_WIDTH/2;
            // add the % part to the position
            tempX+= (tempX/(mMaxX+CAMERA_WIDTH))*CAMERA_WIDTH;      
            //set the position
            //scrollBar.setPosition(tempX, scrollBar.getY());

            //set the arrows for left and right
            menuright.setPosition(mCamera.getCenterX()+CAMERA_WIDTH/2-menuright.getWidth(),menuright.getY());
            menuleft.setPosition(mCamera.getCenterX()-CAMERA_WIDTH/2,menuleft.getY());



            //Because Camera can have negativ X values, so set to 0
            if(this.mCamera.getXMin()<0){
                this.mCamera.offsetCenter(0,0);
                mCurrentX=0;
            }


        }

the problem is that i use this as my second scene in the Activity,
So when i navigate back to the first activity the first scene is out of position because of the camera being moved.

Is there anyway i can reset the camera when going back to the first scene?

I tried Camer.reset() to no avail.

Any suggestions?

Answer 1

Use mCamera.setCenter(CAMERA_WIDTH / 2, CAMERA_HEIGHT / 2);. It will reset the camera position.

By the way, I see you keep changing the menu arrows according to the camera position. You know, AndEngine has a class to handle this case 🙂 You have no reason to do it manually…
It’s called HUD, which means Head-Up Display. You can extend the HUD class, a HUD is just a scene which is placed in a constant position on the screen. You can add as many entities to it as you want. Then, just call mCamera.setHUD(Your HUD object here); and you are done, no need to mess around with moving entities across the camera.

Another issue I see is, you call mCamera.offsetCenter(0, 0);. offsetCenter simply adds the parameters to the current center coordinates. Adding 0 has no influence at all, so this call is useless. What are you trying to achieve? Reset the camera back to (0, 0)?

EDIT:

Here is a HUD example from my own game:

public class AttackControl extends HUD {
// ===========================================================
// Constants          
// ===========================================================

// ===========================================================          
// Fields         
// =========================================================== 
private Sprite mSprite;
private IAttackControlClickListener mListener;
// ===========================================================          
// Constructors          
// =========================================================== 
public AttackControl(final float pX, final float pY, final Camera pCamera, final TextureRegion pTextureRegion, final IAttackControlClickListener pListener) {
    super.setCamera(pCamera);
    this.mListener = pListener;
    this.mSprite = new Sprite(pX, pY, pTextureRegion) {
        @Override
        public boolean onAreaTouched(final TouchEvent pTouchEvent, final float pX, final float pY) {
            AttackControl.this.mListener.onClick();
            return true;
        }
    };
    super.attachChild(this.mSprite);
    super.registerTouchArea(this.mSprite);
}
// ===========================================================          
// Getter & Setter          
// =========================================================== 

// ===========================================================          
// Methods for/from SuperClass/Interfaces          
// ===========================================================  

// ===========================================================          
// Methods          
// ===========================================================  

// ===========================================================          
// Inner and Anonymous Classes          
// ===========================================================  
public interface IAttackControlClickListener {
    public void onClick();
}
} 

Then you create an instance of this class:

final AttackControl attackControl = new AttackControl(...);

and set it as the camera’s HUD:

mCamera.setHUD(attackControl);

In any case you want to use more than 1 HUD, you set 1 as a HUD then make the next one be the first one’s child scene. For example, If I have another HUD called DisplayStats and I have created it this way:

final DisplayStats displayStats = new DisplayStats(...);

Then, just set it as the attack control’s child scene. Remember – a HUD is scene! All scene operations are legal here.

attackControl.setChildScene(displayStats);

And now, the next HUD could be the child scene of displayStats… And so on.