android - 从下到上展开动画

Question

我使用了代码：

 public static void expand(final View v) {
    v.measure(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    final int targtetHeight = v.getMeasuredHeight();

    v.getLayoutParams().height = 0;
    v.setVisibility(View.VISIBLE);
    Animation a = new Animation()
    {


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

        @Override
        protected void applyTransformation(float interpolatedTime,
                Transformation t) {

            v.getLayoutParams().height = interpolatedTime == 1
                    ? LayoutParams.WRAP_CONTENT
                    : (int)(targtetHeight * interpolatedTime);
            v.requestLayout();
        }
    };

    // 1dp/ms
    a.setDuration((int)(targtetHeight / v.getContext().getResources().getDisplayMetrics().density));
    v.startAnimation(a);
}

效果是从上到下的，我想用从下到上的动画