How can I populate my RecyclerView from multiple nodes of my Firebase Realtime Database?

Question

I am looking for a way to populate my RecyclerView. I know how to populate a RecyclerView from a single node of my database but I wonder how can I get data from multiple nodes. In my app the user can select multiple hobbies. And I want to populate a recycler view depending which hobbies the user has selected.

Here is a picture of my user node from my database

As you can see my user has selected the hobbies Caffe's,Camping,Hiking

I have a node called Locations and there a six child nodes Caffe's,Camping,Hiking,Museums,Night life and restaurants. Here is my Locations node

I get users hobbies from this code block

 val currentuid = FirebaseAuth.getInstance().currentUser!!.uid
        val getCurrentUserHobbies =
            FirebaseDatabase.getInstance().getReference("users/$currentuid/hobbies")
        getCurrentUserHobbies.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                val value = snapshot.getValue(String::class.java)
                val valueAsString = value.toString()
                if (valueAsString.contains("Hiking")){

                }

            }

            override fun onCancelled(error: DatabaseError) {

            }

        })

If I want to get my recycler view to show all Hiking locations I do this:

  val adapter = GroupAdapter<GroupieViewHolder>()

        val hikingRef = FirebaseDatabase.getInstance().getReference("Locations/Hiking")
        hikingRef.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                for (snap in snapshot.children) {
                    val recommendItems = snap.getValue(RecommendationsClass::class.java)
                    if (recommendItems != null) {
                        adapter.add(RecommendationsAdapter(recommendItems))
                    }
                }
                recommendationsRecyclerView.adapter = adapter
            }

            override fun onCancelled(error: DatabaseError) {
            }
        })

Now if the user has selected hiking and camping for example. I want my recycler view to show all locations from nodes Locations/Hiking and Locations/Camping. I tried multiple but nothing works. I am not going to write them here because it will take too much space. I am trying to keep my question as simple as possible.

Thanks in advance!

Answer 1

I unfortunately could not find any possible solution how to make it work. I had to do something different. What I did I copied sub nodes from my Locations node and put them in users/currentuid/Recommendations depending which hobbies my current user has.

Here is the code snipped that does that:

 val currentuid = FirebaseAuth.getInstance().currentUser!!.uid
        val getCurrentUserHobbies = FirebaseDatabase.getInstance().getReference("users/$currentuid/hobbies")
        getCurrentUserHobbies.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                val value = snapshot.getValue(String::class.java)
                val valueAsString = value.toString()
                if (valueAsString.contains("Caffe's")) {
                    val ref = FirebaseDatabase.getInstance().getReference("Locations/Caffe's/")
                    ref.addListenerForSingleValueEvent(object : ValueEventListener {
                        override fun onDataChange(dataSnapshot: DataSnapshot) {
                            for (snap in dataSnapshot.children) {
                                val data = dataSnapshot.value
                                val newData = mapOf("Recommendations/${dataSnapshot.key}" to data)
                                FirebaseDatabase.getInstance().getReference("users")
                                    .child(currentuid).updateChildren(newData)
                            }
                        }

                        override fun onCancelled(databaseError: DatabaseError) {
                            // Handle error
                        }
                    })
                }
                if (valueAsString.contains("Camping")) {
                    val ref = FirebaseDatabase.getInstance().getReference("Locations/Camping/")
                    ref.addListenerForSingleValueEvent(object : ValueEventListener {
                        override fun onDataChange(dataSnapshot: DataSnapshot) {
                            for (snap in dataSnapshot.children) {
                                val data = dataSnapshot.value
                                val newData = mapOf("Recommendations/${dataSnapshot.key}" to data)
                                FirebaseDatabase.getInstance().getReference("users")
                                    .child(currentuid).updateChildren(newData)
                            }
                        }

                        override fun onCancelled(databaseError: DatabaseError) {
                            // Handle error
                        }
                    })
                }
                if (valueAsString.contains("Hiking")) {
                    val ref = FirebaseDatabase.getInstance().getReference("Locations/Hiking/")
                    ref.addListenerForSingleValueEvent(object : ValueEventListener {
                        override fun onDataChange(dataSnapshot: DataSnapshot) {
                            for (snap in dataSnapshot.children) {
                                val data = dataSnapshot.value
                                val newData = mapOf("Recommendations/${dataSnapshot.key}" to data)
                                FirebaseDatabase.getInstance().getReference("users")
                                    .child(currentuid).updateChildren(newData)
                            }

                        }

                        override fun onCancelled(databaseError: DatabaseError) {
                            // Handle error
                        }
                    })
                }

            }

            override fun onCancelled(error: DatabaseError) {

            }
        })

What the code above does it checks if caffe's camping and hiking exists in my users/currentuid/hobbies node. If it does it copies the data from Locations and puts it in users/currentuid/Recommendations.

Note: I also have to check for remaining three hobbies. I only put three of them for testing purposes.

Here is also an image to show what I did

After this I only looped through my Recommendations node and added all the locations to my recycler view with this code snippet:

  val recommendedLocations = FirebaseDatabase.getInstance().getReference("users/$currentuid/Recommendations")
        recommendedLocations.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                for (parentSnapshot in snapshot.children) {
                    for (childSnapshot in parentSnapshot.children) {
                        val recommendItems = childSnapshot.getValue(RecommendationsClass::class.java)
                        if (recommendItems != null) {
                            adapter.add(RecommendationsAdapter(recommendItems))
                        }
                    }
                }
                recommendationsRecyclerView.adapter = adapter
            }
            override fun onCancelled(error: DatabaseError) {
            }
        })