TextView not able to setText with data from Firestore

Question

I'm fetching data from Firestore. I want to set the string data to a TextView. I'm able to get the data successfully . i.e I'm able to log it in the logcat. But when I try to set the text,it shows null in place of the data

Here is my code :

@Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        yourSector=view.findViewById(R.id.Sector_tv);
        yourPincode=view.findViewById(R.id.Pincode_tv);

        DocumentReference docRef = db.collection("customerUsers").document(userID);
        docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                    DocumentSnapshot document = task.getResult();
                    if (document.exists()) {
                        pincode = document.getString("pincode");
                        sector = document.getString("sector");
                        Log.d("pincodetest", "onComplete: "+pincode);

                    } else {
                        Log.d("docref", "No such document");
                    }
                } else {
                    Log.d("docref", "get failed with ", task.getException());
                }
            }
        });

        String sectorText="Sector : " + sector;
        String pincodeText="Pincode : "+pincode;
        yourSector.setText(sectorText);
        yourPincode.setText(pincodeText);

My logcat (shows the correct data):

2020-06-14 00:41:43.779 14633-14633/? D/pincodetest: onComplete: 110001

When I set the text, on my screen I get: Sector : null

PS: Strings pincode,sector have already been declared outside onViewCreated

Answer 1

The OnCompleteListener completes asynchronously so you need to place your setTexts within the onComplete method of it. In other words, the sector and pincode local variables are not populated with data when they are accessed for the concatenation to form the sectorText and pincodeText Strings.

In simpler terms, the onComplete method runs after the string concatenation. Therefore, during the string concatenation the value of the variables sector and pincode are still null.

I've done a little fix in the code below:

if (document.exists()) {
    pincode = document.getString("pincode");
    sector = document.getString("sector");
    Log.d("pincodetest", "onComplete: "+pincode);

    String sectorText="Sector : " + sector;
    String pincodeText="Pincode : "+pincode;
    yourSector.setText(sectorText);
    yourPincode.setText(pincodeText);

}