How to check if the custom DialogFragment is displayed?

Question

1) In my application, the user may receive a lot of notifications from FCM
2) If the user has an application open, he needs to display the custom DialogFragment
3) If the DialogFragment is already displayed, then the next time the notification arrives, it is necessary to prohibit the repeated display of this DialogFragment
4) My dialogue code:

public final class NotificationEventDialog extends DialogFragment implements DialogInterface.OnKeyListener, View.OnClickListener {
    private Activity mCurrentActivity;
    private NotificationEventDialogListener mNotificationEventDialogListener;

    public interface NotificationEventDialogListener {
        void showEvent();
    }

    public NotificationEventDialog() {
    }

    public static NotificationEventDialog newInstance() {
        NotificationEventDialog notificationEventDialog = new NotificationEventDialog();
        notificationEventDialog.setCancelable(false);
        return notificationEventDialog;
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        mCurrentActivity = (Activity)context;
        try {
            mNotificationEventDialogListener = (NotificationEventDialogListener) mCurrentActivity;
        } catch (ClassCastException e) {
            throw new ClassCastException(mCurrentActivity.toString() + " must implemented NotificationEventDialogListener");
        }
    }

    @NonNull
    @Override
    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
        LayoutInflater inflater = LayoutInflater.from(mCurrentActivity);
        @SuppressLint("InflateParams") View view = inflater.inflate(R.layout.dialog_notification_event, null);

        Button btnNotificationEventYes = view.findViewById(R.id.notification_event_dialog_yes);
        btnNotificationEventYes.setOnClickListener(this);

        Button btnNotificationEventNo = view.findViewById(R.id.notification_event_dialog_no);
        btnNotificationEventNo.setOnClickListener(this);

        AlertDialog.Builder builder = new AlertDialog.Builder(mCurrentActivity);
        builder.setView(view);

        return builder.create();
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if (getDialog() != null && getDialog().getWindow() != null) {
            getDialog().getWindow().requestFeature(Window.FEATURE_NO_TITLE);
            getDialog().setOnKeyListener(this);
        }
        return super.onCreateView(inflater, container, savedInstanceState);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mCurrentActivity = null;
        mNotificationEventDialogListener = null;
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.notification_event_dialog_yes:
                dismiss();
                mNotificationEventDialogListener.showEvent();
                break;
            case R.id.notification_event_dialog_no:
                dismiss();
                break;
        }
    }

    @Override
    public boolean onKey(DialogInterface dialog, int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK)) {
            dismiss();
            return true;
        } else return false;
    }
} 

5) Each time I receive a notification from FCM, I create a dialog box:

DialogFragment notificationEventDialog = NotificationEventDialog.newInstance();  
notificationEventDialog.show(getSupportFragmentManager(), "");  

6) How to check if DialogFragment is already displayed? Every time I create a new object of this window and I cannot make it as Singleton, because This leads to a memory leak.

Found an answer in which a person suggests using Weak links to solve this problem:

Also you can store a weak link to the shown dialog in that singletone class. Using such method, you can detect is your dialog currently shown or not.

There was also such an answer:

I suggest to save link to the dialog in single instance class. In that instance create method ensureShowDialog(Context context). That method would check is current shown dialog or not. If yes, you can show the dialog. In another casr you can pass new data you to the dialog.

But, honestly, I can’t quite understand how to use these tips in practice. Please can help with this realization or suggest another way? Thanks in advance.

Answer 1

You can use:

    val ft: FragmentTransaction = fragmentManager!!.beginTransaction()
    val prev: Fragment? = fragmentManager!!.findFragmentByTag("typeDialog")

    if (prev == null) {
        val fm = fragmentManager
        val courseTypeListDialogFragment =
            CourseTypeListDialogFragment()
        courseTypeListDialogFragment.isCancelable = false
        courseTypeListDialogFragment.setStyle(
            DialogFragment.STYLE_NO_TITLE,
            0
        )
        courseTypeListDialogFragment.setTargetFragment(this, 1)
        if (fm != null) {
            courseTypeListDialogFragment.show(ft, "typeDialog")
        }
    }

Answer 2

You can check if dialog fragment is showing by calling isAdded () inside DialogFragment or by

DialogFragment notificationEventDialog = NotificationEventDialog.newInstance();
notificationEventDialog.isAdded()

from activity

It will return true if fragment is added to an Activity, in case of dialog fragment - is shown.

You can store last shown dialog fragment date via putting System.currentTimeMillis() in SharedPreferences

I think you'v got the idea.