update data in real time from Firestore-CodePudding

Basically, I created an Android app where users recharge then values of the Firestore was changes to a new value but if the android app did not change it will need to change activity or relaunch the app the values were updated but I want the values updated in Real-time that reflects in the Android app.

Here's my code:

DocumentReference reference = 
FirebaseFirestore.getInstance().collection("Users").document(mobile);
    reference.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
        @Override
        public void onComplete(@NonNull Task<DocumentSnapshot> task) {
            if (task.isSuccessful()) {
                DocumentSnapshot snapshot = task.getResult();
                if (snapshot.getString("Wallet") != null) {
                    String wallet = snapshot.getString("Wallet");
                    walletshow.setText(wallet);     // This value was update in real time if his wallet changes to
                } else {                            // 100₹ to 150₹ the user need to relaunch or change the activity to refresh the values
                    walletshow.setText("Activate your account !");
                    walletshow.setTextColor(Color.RED);
                    Log.d("LOGGER", "No such document");
                }
            } else {
                Log.d("LOGGER", "get failed with ", task.getException());
                walletshow.setText("Login Again");
            }
        }
    });

That's it

CodePudding user response：

Basically I created an Android app where the user recharges then the values of the Firestore were changes to a new value but in the Android app was no changes.

That's the expected behavior since you are using a DocumentReference#get() call which only:

Reads the document referenced by this DocumentReference.

If you want to listen for real-time updates, then you should consider using DocumentReference#addSnapshotListener() which:

Starts listening to the document referenced by this DocumentReference.

As explained in the official documentation:

https://firebase.google.com/docs/firestore/query-data/listen

And in code that would be:

reference.addSnapshotListener(new EventListener<DocumentSnapshot>() {
    @Override
    public void onEvent(@Nullable DocumentSnapshot snapshot,
                        @Nullable FirebaseFirestoreException e) {
        if (e != null) {
            Log.w(TAG, "Listen failed.", e);
            return;
        }

        if (snapshot != null && snapshot.exists()) {
            Log.d(TAG, "Current data: "   snapshot.getData());
        } else {
            Log.d(TAG, "Current data: null");
        }
    }
});