Expand Animation to work on both sides? (on negative axis)

Question

I implemented an ExpandAnimation on view like this:

        @Override
    protected void applyTransformation(float interpolatedTime,
                                       Transformation t) {
        LayoutParams lp =
                (LayoutParams) view.getLayoutParams();
        if(rightAnimation){
            lp.width = (int) (mStartWidth + mDeltaWidth *
                    interpolatedTime);
            view.setLayoutParams(lp);
        }else{

        }

    }

With this animation my view expands and shrinks.

What i want to do is to implement this animation to the other side (to -x side) as well. But i get confused a little bit, since shrinking the width will not work. (Since minus widths or heights are not allowed)

Does anyone know a better way to implement expand animation to the left (-x) or up(-y) side as well?

Or maybe mirroring the view?

Answer 1

Finally I achieved to make a left hand side expand animation. Here is the code:

   private class ExpandAnimation extends Animation implements Animation.AnimationListener {
    private final int mStartWidth;
    private final int mDeltaWidth;
    int delta;

    public ExpandAnimation(int startWidth, int endWidth) {
        mStartWidth = startWidth;
        mDeltaWidth = endWidth - startWidth;
        RelativeLayout.LayoutParams param = (RelativeLayout.LayoutParams) getLayoutParams();
        delta = param.width;
        setAnimationListener(this);
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        RelativeLayout.LayoutParams param = (RelativeLayout.LayoutParams) getLayoutParams();
        delta = param.width;
        if(param.width <= 0){
            delta = 0;
        }
        param.width = (int) (mStartWidth + mDeltaWidth *
                interpolatedTime);
        if(delta != 0){
            delta = (int) (mStartWidth + mDeltaWidth *
                    interpolatedTime) - delta;
        }
        param.leftMargin -=delta;
        setLayoutParams(param);
    }

    @Override
    public boolean willChangeBounds() {
        return true;
    }

    @Override
    public void onAnimationStart(Animation animation) {
    }

    @Override
    public void onAnimationEnd(Animation animation) {
        setText(text);
        requestLayout();
        mExpanded = !mExpanded;
    }

    @Override
    public void onAnimationRepeat(Animation animation) {

    }
}

For a reason that I don't know, width comes as -2 in the start. So i filter out that by an if. Apply Transformation method does the job.