Pretty Cool Animation

mShowAnswer can be exchanged for any view. In this case it's a button.

    private void showAnswerAnimation() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            int cx = mShowAnswer.getWidth() / 2;
            int cy = mShowAnswer.getHeight() / 2;
            float radius = mShowAnswer.getWidth();
            Animator anim = ViewAnimationUtils
                    .createCircularReveal(mShowAnswer, cx, cy, radius, 0);
            anim.addListener(new AnimatorListenerAdapter() {
                                 @Override
                                 public void onAnimationEnd(Animator animation) {
                                     super.onAnimationEnd(animation);
                                     mAnswerTextView.setVisibility(View.VISIBLE);
                                     mShowAnswer.setVisibility(View.INVISIBLE);
                                 }
                             }
            );
            anim.start();
        } else {
            mAnswerTextView.setVisibility(View.VISIBLE);
            mShowAnswer.setVisibility(View.INVISIBLE);
        }
    }