Calling Viewpager Fragment's Function on it's Visibility - Solid Solution.

ViewPagerFirstFragment.class

private boolean notFirstTime;

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser && notFirstTime) {
            //TODO: Call function to be executed every time.
            requestData();
        }
    }

    @Override
    public void onResume() {
        super.onResume();
        notFirstTime = true;
        if (getUserVisibleHint()) {
            //TODO: Call function to be executed every time.
            requestData();
        }
    }