Android studio how to use multiple snapshots in a class

Question

I'm trying to do snapshot from two different child sections from database.

private String name;
snap1.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        name = value
    }

    snap2.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) { 
            if(value.equals(name)) {
                //Do this
            }
        }
    }
}

But after first snapshot is done, name is null . I see inside of onDataChange name is not null. How can I store value into name and use it for the second datasnapshot?

Answer 1

Firebase calls are Asynch, you have to wait for the first call to end before calling the second one. I don't know about the perfect way to do this but I made a function and placed one of my call inside it and called that function inside the first call. You can do your work something like this:

private String name;
snap1.addListenerForSingleValueEvent(new ValueEventListener() {
  @Override
  public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
   name = value
   secondCall();
  }
}

//The function with second call
secondCall(){
  snap2.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) { 
      if(value.equals(name)){
        //Do this
      }
    }
  }      
}