Android java.lang.IllegalStateException: Fragment déjà ajouté

Je reçois un objet de chargement en attente d'une requête du webservice. Mais parfois, cet objet entraîne la fin de mon application. Je n'ai pas pu détecter exactement ce qu'impliquait l'erreur.

Pour éviter cette erreur, j'ai appelé l'objet "ignorer" et "annuler" en passant l'activité, mais cela n'a pas fonctionné. J'ai alors assigné une valeur de "null" qui n'a pas fonctionné non plus. Je n'ai plus travaillé parce que je pensais avoir affaire à Tag.

Mon code d'erreur;

    public class DelayedProgressDialog extends DialogFragment {
    private static final int DELAY_MILLISECOND = 450;
    private static final int MINIMUM_SHOW_DURATION_MILLISECOND = 300;
    private static final int PROGRESS_CONTENT_SIZE_DP = 80;

    private ProgressBar mProgressBar;
    private boolean startedShowing;
    private long mStartMillisecond;
    private long mStopMillisecond;

    private FragmentManager fragmentManager;
    private String tag;
    private Handler showHandler;

    // default constructor. Needed so rotation doesn't crash
    public DelayedProgressDialog() {
        super();
    }

    @NonNull
    @SuppressLint("InflateParams")
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        LayoutInflater inflater = getActivity().getLayoutInflater();

        builder.setView(inflater.inflate(R.layout.dialog_progress, null));
        return builder.create();
    }

    @Override
    public void onStart() {
        super.onStart();
        mProgressBar = getDialog().findViewById(R.id.progress);

        if (getDialog().getWindow() != null) {
            int px = (int) (PROGRESS_CONTENT_SIZE_DP * getResources().getDisplayMetrics().density);
            getDialog().getWindow().setLayout(px, px);
            getDialog().getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        }
    }

    @Override
    public void show(FragmentManager fm, String tag) {
        if (isAdded())
            return;

        this.fragmentManager = fm;
        this.tag = tag;
        mStartMillisecond = System.currentTimeMillis();
        startedShowing = false;
        mStopMillisecond = Long.MAX_VALUE;

        showHandler = new Handler();
        showHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                // only show if not already cancelled
                if (mStopMillisecond > System.currentTimeMillis())
                    showDialogAfterDelay();
            }
        }, DELAY_MILLISECOND);
    }

    private void showDialogAfterDelay() {
        startedShowing = true;

        DialogFragment dialogFragment = (DialogFragment) fragmentManager.findFragmentByTag(tag);
        if (dialogFragment != null) {
            fragmentManager.beginTransaction().show(dialogFragment).commitAllowingStateLoss();
        } else {
            FragmentTransaction ft = fragmentManager.beginTransaction();
            ft.add(this, tag);
            ft.commitAllowingStateLoss();
        }
    }

    public void cancel() {
        if(showHandler == null)
            return;

        mStopMillisecond = System.currentTimeMillis();
        showHandler.removeCallbacksAndMessages(null);

        if (startedShowing) {
            if (mProgressBar != null) {
                cancelWhenShowing();
            } else {
                cancelWhenNotShowing();
            }
        } else
            dismiss();
    }

    private void cancelWhenShowing() {
        if (mStopMillisecond < mStartMillisecond + DELAY_MILLISECOND + MINIMUM_SHOW_DURATION_MILLISECOND) {
            final Handler handler = new Handler();
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    dismiss();
                }
            }, MINIMUM_SHOW_DURATION_MILLISECOND);
        } else {
            dismiss();
        }
    }

    private void cancelWhenNotShowing() {
        final Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                dismiss();
            }
        }, DELAY_MILLISECOND);
    }

    @Override
    public void dismiss() {
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.remove(this);
        ft.commitAllowingStateLoss();
    }
}

Ma classe de dialogue de progression d'utilisation; p >

2019-03-27 11:51:20.502 29685-29685/com.xxxx.app E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.xxxx.app, PID: 29685
    java.lang.IllegalStateException: Fragment already added: DelayedProgressDialog{d8bd442 #1 Delaleyed}
        at androidx.fragment.app.FragmentManagerImpl.addFragment(FragmentManager.java:1916)
        at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:765)
        at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at androidx.fragment.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:6981)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)