Question

I am learning Android and java so this is probably an easy question.

I am trying to call invalidate() on my DrawView. I have read up on it and I think the problem is that I cannot call invalidate outside of the UI thread (or something). As far as I know I only have one thread running as this is a simple TicTacToe game. so here is my code.

DrawView dv;

Create the dv object to associate it with the DrawView class

dv.invalidate();

trying to call the invalidate method.

This is the first part of my DrawView class

class DrawView extends View implements OnTouchListener, OnGestureListener
{
    public DrawView(Context context)
    {
        super(context);
        this.setOnTouchListener(this);

    }

    @Override
    protected void onDraw(Canvas canvas)
    {
                    canvas.drawColor(0xFF303030);
        Paint paint = new Paint();
        paint.setColor(0xFFFFFFFF);
        board.draw(canvas);
        detectEnd();
    }

it seems as if invalidate IS called however it crashes the program. Any ideas?

EDIT: I tried dv.postInvalidate()however it throws a null pointer exception. I have tried to initialize the DrawView dv in several ways but to no avail.

Answer 1

If you are calling invalidate from outside the DrawView, you have to call postInvalidate() instead.

Also, it generally isn’t ever a good idea to play sounds during the onDraw method.