无法从具有无效结果类型的方法返回值

Question

I'm trying to get a specific value from Firebase database, and I did it before, but now when I'm trying something a bit different, it says "Cannot return value from a method with void result type".

I can guess that I'm missing some programming rules because I'm a new Java programmer.

This is my code:

public int getVotesForEvent(final String event_title) {
    firebaseRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.child("Votes").exists()) {

                for (DataSnapshot event : dataSnapshot.child("Votes").getChildren()) {
                    String event_title2 = event.getKey();
                    if (event_title2.equals(event_title)) {
                        int count=Integer.parseInt(event.getValue().toString());
                        return count;

                    }


                }

            }
            else {
                int count = 0 ;
                return count;
            }
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });
}

The error appears where I'm trying to return count.

After reading comments, this is my code and now the method doesn't effect the declared variable count, it keeps 0:

  int count=0;
public int getVotesForEvent(final String event_title) {

    firebaseRef.addValueEventListener(new ValueEventListener() {

        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            if (dataSnapshot.child("Votes").exists()) {
                boolean flag=false;
                for (DataSnapshot event : dataSnapshot.child("Votes").getChildren()) {
                    String event_title2 = event.getKey();
                    if (event_title2.equals(event_title)) {
                        flag=true;
                        Toast.makeText(EventInfo.this, ""+Integer.parseInt(event.child("event_votes").getValue().toString()), Toast.LENGTH_SHORT).show();
                        count=Integer.parseInt(event.child("event_votes").getValue().toString());


                    }


                }
                if(flag!=true)
                {
                    count=0;
                }

            }
            else
            {
                count=0;
            }

        }



        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }

    });
    return count;

}

What am I doing wrong now?

Answer 1

In java method with void means that method return nothing.

onDataChange return type is void , you can not return value count .

Remove return statement and Try saving count value in a field if you need it

Answer 2

Your onDataChange method is marked void, yet you are trying to return from it. Remove the return lines and save the value in a variable for further usage.

Answer 3

As others have written, you cant return from void method type. But i think I you are getting confused here because of following, there are two methods here in your code,

public int getVotesForEvent(final String event_title)
public void onDataChange(DataSnapshot dataSnapshot)

The first one will accept return type as integer (ie int). Other one expects no return type.

The second method is where you have written 'return count' and hence it fails.