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Below is the structure of my Firebase Realtime Database:

enter image description here

I want to get Contacts from the phone in which the app is running. Then I want to check if any of the contact's phone number is in the database. Or in other words, if a user with that particular number exists or not. If it exists, I want to put the contact in a HashMap whose key is the number and name is the value. I will later add this HashMap data to RecyclerView.

I am able to get the contacts and also check the above condition, but it does not add them to the HashMap. Below is my code for getting contacts and checking:

@SuppressLint("Range")
private void getContacts() {
    @SuppressLint("Recycle")
    Cursor cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
            null, null, null, null);
    while (cursor.moveToNext()) {
        String name = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
        String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
        number = number.trim();

        Pattern p = Pattern.compile(
                "^(\\+\\d{1,3}( )?)?((\\(\\d{1,3}\\))|\\d{1,3})[- .]?\\d{3,4}[- .]?\\d{4}$");

        Matcher m = p.matcher(number);

        if (m.find()) {
            if (exists(number).equalsIgnoreCase(number)) {
                Log.i("Does match:", number);
                contactList.put(number, name);
            } else {
                Log.wtf("Does not match:", number);
            }
        }
    }
}

private String exists(String number) {
    final String[] numberF = {""};

    if (number.length() > 10 && number.length() <= 15) {
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("users");
        reference.child(number).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                if (snapshot.exists()) {
                    String numberDB = snapshot.child("number").getValue(String.class);
                    numberF[0] = numberDB;
                } else {
                    numberF[0] = "";
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                numberF[0] = "";
            }
        });
    } else {
        numberF[0] = "";
    }

    return numberF[0];
}

Please help me out to check the above condition or tell why it is not added to the HashMap.

vAayush3301
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    I'm not sure I understand. What exactly in this code doesn't work the way you expect? Tell us what is wrong with shared code. Do you have any errors? – Alex Mamo Jul 10 '23 at 12:05
  • Data is loaded from Firebase (and pretty much any cloud API) asynchronously, and your main code will continue to run while the data is being loaded. Then when the data is available, your `onDataChange` is called. What this means is that when your `return numberF[0]` runs, none of the `numberF[0] = numberDB;` has yet been called. You can verify this by setting breakpoints and running in the debugger. --- In practice it means that you can't return a value that is asynchronously loaded and will need to handle it inside the `onDataChange`. A common workaround is to pass a custom callback. – Frank van Puffelen Jul 10 '23 at 14:01

0 Answers0