Update:
I figured out that the reason was that the @Override method itself was misconstrued. Although this is a duplicate question the answer is still available for StackOverflow members to use.
In your activity you must declare the @Override as follows:
@Override
public void onBackPressed() {
overridePendingTransition(R.anim.disappear, R.anim.appear);
finish();
super.onBackPressed();
Hope that clears up any discrepancy.