Apps (Help) Pressing back on webview fragment activity does not go back to previous page

[unet]

Hello.
I have an app that has fragment activities with webview and a navigational drawer. When I press back it goes to a previous fragment activity but it does not go back to the previous page on the webview.

The code on MainActivity.java:

 @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.nav_facebook:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new FacebookFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_twitter:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new TwitterFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_instagram:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new InstagramFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_linkedin:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new LinkedinFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_snapchat:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new SnapchatFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_pinterest:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new PinterestFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_youtube:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new YoutubeFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_about:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new AboutFragment()).addToBackStack("tag").commit();
                break;
            case R.id.nav_privacy:
                getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                        new PrivacyFragment()).addToBackStack("tag").commit();
                break;
        }

        drawer.closeDrawer(GravityCompat.START);

        return true;
    }


    @Override
    public void onBackPressed() {
        FragmentManager fm = getSupportFragmentManager();
        if (fm.getBackStackEntryCount() > 0) {
            fm.popBackStack();
        } else {
            super.onBackPressed();
        }
    }

The code in one of the fragments (FacebookFragment.java):

public class FacebookFragment extends Fragment {
    public FacebookFragment() {

    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_facebook, container, false);
        WebView webView = (WebView)v.findViewById(R.id.webView);
        webView.getSettings().setJavaScriptEnabled(true);
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("https://www.facebook.com/");
        return v;



    }





}