Question

I’m using the framework intorduced in the Beginning Android Games book,
It has a method called drawPixmap(), its definition is:

@Override
public void drawPixmap(Pixmap pixmap, int x, int y) {
    canvas.drawBitmap(((AndroidPixmap)pixmap).bitmap, x, y, null);
}

When I’m calling the function, let’s say

g.drawPixmap(Assets.ball,200,200);

It works.
but when I use it like this

g.drawPixmap(Assets.ball,ball.getX(),ball.getY());

It doesn’t.

I tried getting the X & Y to a local variable before, still no good.
both X and Y in the ball class are integers.

In the book, he shows a code which includes using variables. but I can’t get this to work.

any ideas why it won’t recognize my cute little variables?

Edit 1:

Now I noticed that in the constructor of that class, it does uses variables successfully.
only in the update() method it doesn’t.

Edit 2:

I get a runtime error:

Fatal Exception Thread-10 java.lang.NullPointerException 

at com.carmel.android.accelpong.GameScreen.<init>

But now I thing it’s something with the ball class itself, as even when trying to set the X using the setX() methoed, I get the same error.. but it doesn’t bring me any closer to solving this

Answer 1

Your ball variable is null. You are forgetting to initialize it, or somehow rewritting it. Include the code that goes from ball creation to invoking that function for a more detailed answer.