如何在Firebase - Android中更改未知父级的子级值

Question

I'm working on a Firebase chat app. I have been trying to change child value for an unknown parent in Firebase but I can't get it right.

Here is my Firebase database structure:

Firebase database

I want to change the value of "seen" from false to true when the user opens Messages activity.

Each message has a push id which I don't know the value. I want to be able to edit a child of push id.

Here is my code:

DatabaseReference messageRef = mRootRef.child("messages").child(mCurrentUserId).child(mChatUser);

 messageRef.child("seen").setValue(true).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        if (task.isSuccessful()) {
                            Log.d("isseen", "Seen set to true");
                        } else {
                            Log.d("isseen", "Seen not set to true");
                        }


                    }
                });

How best can I achieve my desired results?

Answer 1

To solve this, you need to use a query. So please use the following lines of code:

DatabaseReference messageRef = mRootRef.child("messages").child(mCurrentUserId).child(mChatUser);
Query query = messageRef.orderByChild("seen").equalTo(false);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            ds.child("seen").getRef().setValue(true);
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
    }
};
query.addListenerForSingleValueEvent(valueEventListener);

The result will the change of your seen property from false to true .

If you also consider at some point to try using Cloud Firestore , here you can find a tutorial on how to create a complete and functional Firestore Chat App using Kotlin .