Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

Question

I\'ve been reading the other posts on tracking down the reasons for getting a SIGSEGV in an Android app. I plan to scour my app for possible NullPointers relate

Answer 1

I've encountered this error when I tried to access the 'canvas' outside of onDraw()

    private Canvas canvas;

    @Override
    protected void onDraw(Canvas canvas) {
        this.canvas = canvas;
        ....... }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) { 
            canvas.save(); // here

A very bad practice :/