CODEWITHSUNDEEP
androidfirebaseandroid-recyclerviewfirebase-realtime-database
henrykodev
henrykodev

Reputation: 3084

Access First Firebase Node Data in Firebase Query

I have a Firebase database query returning 100 child nodes. Then I put the nodes into a FirebaseRecyclerAdapter so the data is displayed on a recycler view. This is all working fine. Now I need to access the latest element and its Firebase key, but haven't been able to figure it out (should be easy, I must have missed something obvious). How do I get the latest element and its Firebase key in the returned query or adapter?

To get the 100 child nodes, I use:

Query publishedPostsQuery = mFirebaseDatabase.child("posts").limitToFirst(100);

I then populate a Firebase recycler adapter:

FirebaseRecyclerAdapter adapter = new FirebaseRecyclerAdapter<Post, PostViewHolder>(Post.class, R.layout.post_items, PostViewHolder.class, postsQuery) { ... };

This adapter is then used in a recycler view.

How do I get to the first Post object and its Firebase key through either Query or FirebaseRecyclerAdapter?

My firebase database structure looks like:

-posts
  -KLRDgtNht0iSB6RUGGz
    - author: "author 1"
    - title: "some post"
    - detail: "blah blah"
  -HGze53Sd4RRpFikdIKD
    - author: "author 2"
    - title: "great post"
    - detail: "blah blah blah blah"

The version of Firebase I am using is:

compile 'com.firebaseui:firebase-ui-database:0.4.0'
compile 'com.google.firebase:firebase-database:9.0.2'

Upvotes: 0

Views: 1283

Answers (2)

henrykodev
henrykodev

Reputation: 3084

I figured it out. To find a particular node, in my case the latest post (presented as a Post object based on the given data structure shown on my question), I had to use addListenerForSingleValueEvent to get the Firebase DataSnapshot, then from there I can loop through the children nodes to find what I want.

    Query publishedPostsQuery = mFirebaseDatabase.child("posts")
            .limitToFirst(100);

    publishedPostsQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.getChildrenCount() != 0) {
                Iterable<DataSnapshot> i = dataSnapshot.getChildren();
                for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
                  // Find the particular node (e.g. last node, first node... etc) here and create a object from it.
                  MyPost foundPost = postSnapshot.getValue(MyPost.class);
                  ...
                  ...
                }
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });

    // Assign the query to FirebaseRecyclerAdapter here.

Upvotes: 1

Niels
Niels

Reputation: 755

Using the adapter, you can do it like this:

if (mAdapter.getItemCount() > 0) {
    final Post = mAdapter.getItem(0);
}

You can find the source of the FirebaseRecyclerAdapter here: https://github.com/firebase/FirebaseUI-Android/blob/master/database/src/main/java/com/firebase/ui/database/FirebaseRecyclerAdapter.java

Upvotes: 0

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