Question

I want to draw a infinitely repeating parallax using Cocos2D on Android.
Now, there are some solutions given to this problem in Objective C, but I’m stuck with my implementation in Android. I have tried using

CCSprite background = CCSprite.sprite("background_island.png");
CCTexParams params = new CCTexParams(GL10.GL_LINEAR,GL10.GL_LINEAR,GL10.GL_REPEAT,GL10.GL_REPEAT);
            background.getTexture().setTexParameters(params);

But it only extends the background in 1 direction.
I guess I have to use 2 sprites, such that as soon as 1st finishes, the other starts and vice versa, but I’m stuck with the implementation.

Answer 1

I had the same problem and figured it out.

Try this. Declare the background and offset as a member:

CCSprite _bg;
float _bgOffset;

In your scene constructor:

CGSize winSize = CCDirector.sharedDirector().displaySize();
_bg = CCSprite.sprite("yourbg.png"); // needs to be square, i.e. 256x256
_bg.setTextureRect(0, 0, winSize.width, winSize.height, false);
_bg.getTexture().setTexParameters(GL10.GL_LINEAR, GL10.GL_LINEAR, GL10.GL_REPEAT,
        GL10.GL_REPEAT);
_bg.setAnchorPoint(CGPoint.zero());
this.addChild(_bg);

And in your update(float dt) method:

if (_bgOffset > 2000000000)
    _bgOffset = 0; // don't want problems, do we?
_bgOffset += dt * PIXELS_PER_SECOND; // this can be dynamic if you want
_bg.setTextureRect(0, _bgOffset, _bg.getTextureRect().size.width,
            _bg.getTextureRect().size.height, false);

See “Repeating Backgrounds” in http://www.raywenderlich.com/3857/how-to-create-dynamic-textures-with-ccrendertexture for the Objective C code

If you need to go both ways, you could perhaps start with a non-zero _bgOffset and see if that works.

Hope this helps someone!