How to update total no of child from firebase child node everytime onDataChange from AddSingleValueEventListner?

Question

Below image shows my Firebase database structure:

All data retrieved successfully. Here is my model class.

public class Post
{
    public String lastname;
    public String postid;
    public long timestamp;
    public HashMap<String,Boolean> count;

    public Post()
    {
    }

    public Post(String lastname, long timestamp, String postid,HashMap count)
    {
        this.lastname=lastname;
        this.timestamp=timestamp;
        this.postid=postid;
        this.count=count;
    }

public HashMap<String, Boolean> getCounts() {
        return count;
    }

    public void setCounts(HashMap<String, Boolean> count) {
        this.count = count;
    }

In Main Activity i used to get data

 mAdapter = new PostAdapter(MainActivity.this);

    getAllPost(null);
    postList.addOnScrollListener(new RecyclerView.OnScrollListener() {

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

            if (!recyclerView.canScrollVertically(1))
            {

                loaded=loaded+10;
                if (totalPost== mAdapter.getItemCount())
                {
                    Toast.makeText(MainActivity.this, "no more post", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    getAllPost(mAdapter.getLastItemId());
                }

            }
        }
    });
postList.setAdapter(mAdapter);
private void getAllPost(final String nodeId)
    {
        final Query query;
        final int left= (int) (totalPost-mAdapter.getItemCount());
        Toast.makeText(this, String .valueOf(left), Toast.LENGTH_SHORT).show();


        if (nodeId == null)
        {
            query = PostRef
                    .orderByChild("timestamp")
                    .limitToLast(mPostsPerPage);
        }

        else
        {

            if (left<10)
            {
                query = PostRef
                        .orderByChild("timestamp")
                        .limitToFirst(left);
            }
            else
            {
                Long time=Long.parseLong(nodeId);
                query = PostRef
                        .orderByChild("timestamp").endAt(time)
                        .limitToLast(10);
            }

        }


        query.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                List<Post> userModels = new ArrayList<>();


                for (DataSnapshot userSnapshot : dataSnapshot.getChildren())
                {
                    userModels.add(userSnapshot.getValue(Post.class));

                }
                if (!(nodeId ==null))
                {
                    if (left>10)
                    {
                        userModels.remove(9);
                    }

                }


                Collections.reverse(userModels);
                mAdapter.addAll(userModels);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                throw databaseError.toException();
            }
        });
    }

And in adapter:

      public class PostAdapter extends RecyclerView.Adapter<PostHolder>
    {
        List<Post> mPost;
        Context mContext;
        public PostAdapter(Context c) {
            this.mPost  = new ArrayList<>();
            mContext=c;
        }
        @NonNull
        @Override
        public PostHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
            return new PostHolder(LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.all_post_layout, viewGroup, false));
        }
        @Override
            public void onBindViewHolder(@NonNull final PostHolder postHolder, final int i) {
    final String PostKey=mPost.get(i).getPostid();
            FirebaseAuth mAuth=FirebaseAuth.getInstance();
            final String currentUserID=mAuth.getCurrentUser().getUid();


    final DatabaseReference post=FirebaseDatabase.getInstance().getReference().child("Posts");
         showCounts(postHolder,i);
        setCountsButton(postHolder,i,currentUserID);
        tapOnCounts(postHolder,i,currentUserID,post,PostKey);
        }
private void tapOncounts(final PostHolder postHolder, final int i, final String currentUserID, final DatabaseReference post, final String postKey)
    {
        postHolder.countsButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                if (mPost.get(i).getCounts() !=null)
                {
                    if(mPost.get(i).getCounts().containsKey(currentUserID))
                    {
                        post.child(postKey).child("counts").child(currentUserID).removeValue();
                        postHolder.countsButton.setImageResource(R.drawable.discounts);
                    }
                    else
                    {
                        postHolder.countsButton.setImageResource(R.drawable.counts);
                        post.child(postKey).child("counts").child(currentUserID).setValue(true);
                    }
                }
                else
                {
                    postHolder.countsButton.setImageResource(R.drawable.counts);
                    post.child(postKey).child("counts").child(currentUserID).setValue(true);
                }
            }
        });
    }
    private void setcountsButton(final PostHolder postHolder, int i, String currentUserID)
    {
        if (mPost.get(i).getCounts() !=null)
        {
            if(mPost.get(i).getCounts().containsKey(currentUserID))
            {
                postHolder.countsButton.setImageResource(R.drawable.counts);
            }
            else
            {
                postHolder.countsButton.setImageResource(R.drawable.discounts);
            }
        }
    }
    private void showCounts(PostHolder postHolder, int i)
    {
        if((mPost.get(i).getCounts() !=null))
        {
            postHolder.noOfcounts.setText(String.valueOf(mPost.get(i).getCounts().size()));
        }
        else
        {
            postHolder.noOfcounts.setText("0");
        }
    }
@Override
    public int getItemCount() {
        return mPost.size();
    }
    public void addAll(List<Post> newPost) {
        int initialSize = mPost.size();
        mPost.addAll(newPost);
        notifyItemRangeInserted(initialSize, newPost.size());
    }

    public String getLastItemId() {
        return String.valueOf(mPost.get(mPost.size() - 1).getTimestamp());
    }

}

All is successfully but whenever total no. of child change(new child added OR old child removed) in count node recylerview is not update. It will only update when i tried to go another activity and come to rerun in MainActivity.

Alex Mamo · Answer 1 · 2019-07-09T09:10:10.280

1

To get realtime updates, you should use Query's addValueEventListener(ValueEventListener listener) method:

Add a listener for changes in the data at this location.

When using addListenerForSingleValueEvent(ValueEventListener listener):

Add a listener for a single change in the data at this location.

Edit:

To get the size of your list, please change the following line of code:

holder.count.setText(String.valueOf(mPost.get(i).getCount().size));

to

holder.count.setText(String.valueOf(getItemCount());

edited Jul 09 '19 at 09:10

answered Jul 09 '19 at 08:37

Alex Mamo

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What is not working, what's the behaviour? Do you have an error? – Alex Mamo Jul 09 '19 at 08:43
total child count not change until i come back to mainactivity – Vora Jul 09 '19 at 08:45
Please share the content of your adapter class. – Alex Mamo Jul 09 '19 at 08:45
i added my adapter – Vora Jul 09 '19 at 08:58
i share all of my content here i used pagination is this problem from here ? – Vora Jul 09 '19 at 17:25
I'm afraid I did not understood your question. If it's about pagination, please take a look at my answer from this **[post](https://stackoverflow.com/questions/50741958/how-to-paginate-firestore-with-android)**. – Alex Mamo Jul 09 '19 at 17:34
So did `holder.count.setText(String.valueOf(getItemCount());` get the correct number of items? Does it work now? – Alex Mamo Jul 09 '19 at 17:35
getCount() is getter and getItemCount() returns the size of List post – Vora Jul 09 '19 at 17:41
So isn't this what you want, to get the size of the list? The getter won't help you the way you want. So using `holder.count.setText(String.valueOf(getItemCount());` isn't getting you the correct number? – Alex Mamo Jul 09 '19 at 17:43
i think you are not understanding my question properly.i dont need list size but i need total child of count node as shown in screenshot. please see corrected model class – Vora Jul 09 '19 at 17:44
Have you tried to use `return count.size()` instead of `return likes`? Does it work this way? – Alex Mamo Jul 09 '19 at 17:56
its my mistake in typing – Vora Jul 09 '19 at 18:00
I don't understand you. Does `return count.size()` work? – Alex Mamo Jul 09 '19 at 18:02
its HashMap count size. if anything is wrong please suggest – Vora Jul 09 '19 at 18:08
i need count node total child. therefor i used getCount.size(). and it should be updat onDataChange – Vora Jul 09 '19 at 18:24

Ujjwal Jung Thapa · Answer 2 · 2019-07-09T09:43:10.533

Whenever total number of child changes then your list of Post modal also changes i.e. userModels in your case. Hence whenever your list of model changes your adapter needs to be notified. Hence my guess is to add notifyDataSetChanged to adapter.

Try this:

query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    List<Post> userModels = new ArrayList<>();
    for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
        userModels.add(userSnapshot.getValue(Post.class));
    }
    mAdapter.notifyDataSetChanged(); //<<changes made HERE

}

@Override
public void onCancelled(DatabaseError databaseError) {
}
})

For this to work I hope userModels is instance variable to your MainActivity and is set to mAdapter during initialization.

also as suggested by Alex Mamo. I think you better use addValueEventListener to get realtime continuous updates. — Ujjwal Jung Thapa, Jul 09 '19 at 09:40

How to update total no of child from firebase child node everytime onDataChange from AddSingleValueEventListner?

2 Answers2