Weird behavior about my fragment and activity

I have an application that reads NFC tags (when main button in MainActivity is clicked), then displays the result in a modal. It works well but know, what I'd like to do is create a fragment to use ViewPager (to have nice transition on my future fragments).

But now, at first, I can't hit my main button. Then, when I scan a tag, it put me on other view (or i don't know what, I don't totally understand) and it displays me the result in a modal. At this moment, I'm on the right side of my application with the same view.

After this, I can hit my main button and scan tags, but, i'm on the wrong fragment or something like that and I can only go to the left

here is my code project : https://github.com/elgrusko/nfc_stackoverflow

Or my main code :

package com.example.poissonpane;

public class MainActivity extends FragmentActivity {

    private static final int NUM_PAGES = 2;
    private ViewPager mPager;
    private PagerAdapter pagerAdapter;
    public static int display, result, detect = 0;
    private NfcAdapter nfcAdapter;
    private ImageButton nfcButton;
    private PendingIntent pendingIntent;
    public static IntentIntegrator integrator;
    public ScreenSlidePageFragment scan_fragment;
    public static String link = null;
    public final int CUSTOMIZED_REQUEST_CODE = 0x0000ffff;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Instantiate a ViewPager and a PagerAdapter.
        mPager = (ViewPager) findViewById(R.id.pager);
        pagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
        mPager.setAdapter(pagerAdapter);
    }

    @Override
    public void onBackPressed() {
        if (mPager.getCurrentItem() == 0) {
            // If the user is currently looking at the first step, allow the system to handle the
            // Back button. This calls finish() on this activity and pops the back stack.
            super.onBackPressed();
        } else {
            // Otherwise, select the previous step.
            mPager.setCurrentItem(mPager.getCurrentItem() - 1);
        }
    }

    private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
        public ScreenSlidePagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            Log.d("TOTO", Integer.toString(position));
            switch (position) {
                case 0:
                    return new ScreenSlidePageFragment();
                case 1:
                    return new SecondFragment();
                default:
                    return new ScreenSlidePageFragment();
            }

        }

        @Override
        public int getCount() {
            return NUM_PAGES;
        }
    }

    public void onResume() {
        super.onResume();
        Log.d("TOTO", "onResume() main activity");
        Intent intent = getIntent(); // Recuperer l'intent actuel
        NdefMessage[] msgs;

        // If a NFC tag has been detected once app was closed
        if (detect == 1 && (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction()) || NfcAdapter.ACTION_TECH_DISCOVERED.equals(intent.getAction()))) { // si l'application a ete lancee via une detection NFC du device  (ACTION_NDEF_DISCOVERED, voir AndroidManifest)
            Parcelable[] rawMessages =
                    intent.getParcelableArrayExtra("android.nfc.extra.NDEF_MESSAGES");
            if (rawMessages != null) { // if NDEF in scan
                display = 1;
                resolveIntent(intent); // parser NFC scan
            }  else {
                byte[] empty = new byte[0];
                byte[] id = intent.getByteArrayExtra(NfcAdapter.EXTRA_ID);
                Tag tag = (Tag) intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
                byte[] payload = NdefMessageParser.dumpTagData(tag).getBytes();
                NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN, empty, id, payload);
                NdefMessage msg = new NdefMessage(new NdefRecord[] {record});
                msgs = new NdefMessage[] {msg};
                detect = 0;
                scan_fragment.getResult(msgs);
            }
        }
        NfcAdapter nfcAdapter2 = this.nfcAdapter;
        if (nfcAdapter2 != null) {
            if (!nfcAdapter2.isEnabled()) {
                showWirelessSettings();
            }
            this.nfcAdapter.enableForegroundDispatch(this, this.pendingIntent, (IntentFilter[]) null, (String[][]) null);
        }
    }

    private void showWirelessSettings() { // ask user to enable NFC on his devices
        Toast.makeText(this, "Veuillez activer le service NFC", Toast.LENGTH_SHORT).show();
        startActivity(new Intent("android.settings.WIRELESS_SETTINGS"));
    }

    public void onPause() {
        Log.d("TOTO", "onPause() MainActivity");
        detect = 0;
        super.onPause();
    }


    public void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        setIntent(intent);
        if (detect != 1) {
            resolveIntent(intent);
        }
    }

    private void resolveIntent(Intent intent) {                                                                 // DETECT NFC & PARSING NDEF
        NdefMessage[] msgs;
        String action = intent.getAction();
        Log.d("Infos", getIntent().toString());
        Log.d("Infos", "display = " + display);
        if (display != 1) {
            Animation shake = AnimationUtils.loadAnimation(this, R.anim.shake);
            nfcButton.startAnimation(shake);
            Toast.makeText(this, "Veuillez lancer un scan", Toast.LENGTH_LONG).show();
            return;
        }
        else if ("android.nfc.action.TAG_DISCOVERED".equals(action) || "android.nfc.action.TECH_DISCOVERED".equals(action) || "android.nfc.action.NDEF_DISCOVERED".equals(action)) {
            result = 1;
            Parcelable[] rawMsgs = intent.getParcelableArrayExtra("android.nfc.extra.NDEF_MESSAGES");
            if (rawMsgs != null) {
                msgs = new NdefMessage[rawMsgs.length];
                for (int i = 0; i < rawMsgs.length; i++) {
                    msgs[i] = (NdefMessage) rawMsgs[i];
                }
            } else {
                byte[] empty = new byte[0];
                byte[] id = intent.getByteArrayExtra(NfcAdapter.EXTRA_ID);
                Tag tag = (Tag) intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
                byte[] payload = NdefMessageParser.dumpTagData(tag).getBytes();
                NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN, empty, id, payload);
                NdefMessage msg = new NdefMessage(new NdefRecord[] {record});
                msgs = new NdefMessage[] {msg};
            }
            if (display == 1) {
                scan_fragment.getResult(msgs);
            }
        }
    }

    public void ScanResultModal(String link, StringBuilder tmp_builder) {       // we don't care for the moment
        Log.d("Toto", "ScanResultModal");
       /* Intent i = new Intent(MainActivity.this, RightActivity.class);
        link = tmp_builder.toString();
        i.putExtra("url", link);
        startActivity(i);*/
    }
}

package com.example.poissonpane;

import java.util.List;

import static com.example.poissonpane.MainActivity.link;

public class ScreenSlidePageFragment extends Fragment {

    public MainActivity mainActivity;
    private ImageButton nfcButton;
    ObjectAnimator anim;
    ObjectAnimator anim2;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(
                R.layout.fragment_screen_slide_page, container, false);
        mainActivity = (MainActivity) getActivity();
        Log.d("TOTO", "onCreateView() Fragment");
        MainActivity.display = 1;
        anim = ObjectAnimator.ofFloat(nfcButton, "scaleX", new float[]{0.9f});
        anim2 = ObjectAnimator.ofFloat(nfcButton, "scaleY", new float[]{0.9f});
        nfcButton = (ImageButton) rootView.findViewById(R.id.nfc_button);
        nfcButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                MainActivity.display = 1;
                manageBlinkEffect();
            }
        });
        return rootView;
    }

    public void manageBlinkEffect() {             // Just to make grow and shrink the Button while scanning                                                           // ANIMATION DU LOGO SENZU SUITE A UN CLIC
        anim.setDuration(1000);
        anim.setRepeatMode(ValueAnimator.REVERSE);
        anim.setRepeatCount(9);
        anim.start();
        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationCancel(animation);
                if (MainActivity.result != 1){
                    Animation shake = AnimationUtils.loadAnimation(getContext(), R.anim.shake);
                    Toast.makeText(getContext(), "Aucun badge n'a été détécté !", Toast.LENGTH_SHORT).show();
                    nfcButton.startAnimation(shake);
                }
            }
        });
        anim2.setDuration(1000);
        anim2.setRepeatMode(ValueAnimator.REVERSE);
        anim2.setRepeatCount(9);
        anim2.start();
    }

    public void getResult(NdefMessage[] msgs) {                                                            // MODAL RESULT SCAN NFC
        if (msgs != null && msgs.length != 0) {
            final StringBuilder tmp_builder = new StringBuilder();
            List<ParsedNdefRecord> records = NdefMessageParser.parse(msgs[0]);
            int size = records.size();
            for (int i = 0; i < size; i++) {
                tmp_builder.append(records.get(i).str());
                tmp_builder.append("\n");
            }
            System.out.println(tmp_builder.toString());
            this.anim.cancel();
            this.anim2.cancel();
            MainActivity.display = 0;
            AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
            builder.setTitle("Resultat du scan :");
            builder.setNeutralButton("Visiter", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    ((MainActivity)getActivity()).ScanResultModal(link, tmp_builder);
                }
            });
            builder.setNegativeButton("Copier", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {
                    ClipboardManager clipboard = (ClipboardManager) getActivity().getSystemService(Context.CLIPBOARD_SERVICE);
                    ClipData clip = ClipData.newPlainText("Texte copié", link);
                    clipboard.setPrimaryClip(clip);
                }
            });
            builder.setPositiveButton("Fermer", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int which) {}
            });
            builder.setMessage(tmp_builder.toString());
            builder.create().show();
        }
    }
}

Do you see something wrong in my fragment or something else ?

Sorry for the explication. It's really hard to explain

thanks !