Android：通知Firebase实时数据库中具体数值变化

Question

Following is screenshot of my Firebase realtime database. How can I notify a user whenever the item worker_id is changed?

I've tried the following code, but it notifies about each type of data change. I want notification specific to change in worker_id :

private void CheckDataChange(){
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    DatabaseReference myRef = database.getReference("posts");
    Query query = myRef.orderByChild("workType");
    ValueEventListener valueEventListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Log.d("Firebase","onDatachange");
    
            for(DataSnapshot ds : dataSnapshot.getChildren()) {
                try {
                    if(!ds.child("worker_id").getValue(String.class).equals("0")) {

                        Toast.makeText(MainActivity.this, "Request accepted", Toast.LENGTH_SHORT).show();
                    }

                }catch (Exception ex){
                    Log.e("Firebase",ex.getMessage()+ex.getCause());
                }
            }

        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Log.d("Firebase", databaseError.getMessage());
        }
    };

    query.addValueEventListener(valueEventListener);
}

Answer 1

There is nothing built into Firebase to raise an event only when the worker_id in your current structure changes.

The most common way to implement something like that would be to create a map mapping ds.getKey() to the value of worker_id when onDataChange is first called, and then comparing the value you get against that for any updates.