Back Button on WebView Fragments - not going to previous page

Question

I have WebView in Fragments and in one Fragment just some buttons (not WebView). When Back Button is pressed, I intend to go back to previous page on WebView (on the rest, or when there is no previous page, closing the App is fine). After going through several suggestions here, finally I have come up to this point, but it does not lead to the previous page on pressing Back Button.

I am not sure if it has to do with addToBackStack as in this Stack Overflow post; I am also not sure how to make that work in my case.

public class MyFragment extends Fragment {


    public WebView webView;

    public boolean WebViewGoBack() {
        if(webView.canGoBack()){
            webView.goBack();
            return true;
        }
        return false; //webview cannot go back, so use the method of the BackButton
    }


}

One Fragment is implemented like this:

public class Tab1Fb extends MyFragment  {




    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.tab1fb, container, false);


        webView =(WebView)rootView.findViewById(R.id.webView);

        webView.setWebViewClient(new WebViewClient());
        webView.getSettings().setJavaScriptEnabled(true);
        webView.getSettings().setDomStorageEnabled(true);
        webView.setOverScrollMode(WebView.OVER_SCROLL_NEVER);
        webView.loadUrl("https://www.facebook.com/");


        return rootView;
    }






}

The MainActivity, I have pageradapter and overridden methods:

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    private Fragment mCurrentFragment;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {

        switch (position) {
            case 0:
                Tab1Fb tab1 = new Tab1Fb();
                return tab1;

            case 1:
                Tab2Videos tab2 = new Tab2Videos();
                return tab2;

            case 2:
                Tab3Downloads tab3 = new Tab3Downloads();
                return tab3;

            case 3:
                Tab4Twitter tab4 = new Tab4Twitter();
                return tab4;

            case 4:
                Tab5Contact tab5 = new Tab5Contact();
                return tab5;

            case 5:
                Tab6Support tab6 = new Tab6Support();
                return tab6;

            default:
                return null;

        }
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 6;
    }


    @Override
    public CharSequence getPageTitle(int position) {

        switch (position) {
            case 0:
                return "FACEBOOK";
            case 1:
                return "VIDEOS";
            case 2:
                return "DOWNLOADS";
            case 3:
                return "TWITTER";
            case 4:
                return "CONTACT";
            case 5:
                return "JOIN";

        }

        return null;
    }


    public Fragment getCurrentFragment() {
        return mCurrentFragment;
    }

    @Override
    public void setPrimaryItem(View container, int position, Object object) {
        if (getCurrentFragment() != object) {
            mCurrentFragment = ((Fragment) object);
        }
        super.setPrimaryItem(container, position, object);
    }




}


@Override
public void onBackPressed() {
    switch (mViewPager.getCurrentItem()) {
        case 0:
            if (!webViewGoBack(0)) {
                //do something if webview cannot go back
            }
            break;
        case 1:

            break;
        default:
    }
}



public boolean webViewGoBack(int num) {
    SectionsPagerAdapter adapter = ((SectionsPagerAdapter)mViewPager.getAdapter());

    MyFragment f = (MyFragment )adapter.getCurrentFragment();

    if (f!= null) {
        return f.WebViewGoBack();

    }
    return false;
}