Complex and nested firebase realtime database reading with firebase recycler adapter

Question

The first data node that is immediately there under user id will contain a linked list type data. Each index can contain two parts: data and info. The confusion is due to the unique key -MkqHbtLzqzI... which is there immediately under index data. Each index data will have a list of such a different and dynamic key. Matrix is a List<Float> .

We want to use FirebaseRecyclerAdapter where I will be required to give the type of class under setQuery method. But I am confused how to make equivalent pojo class (or data class in kotlin) of such a structure.

Objects that we want to load in a recyclerView starts from 2 . So, 6154... is a userId under which we have a node called data as shown in the given screenshot. This data contains a list of items in a linkedList<Long> fashion that we want to display in a recyclerView .

I have tried with below data classes but the problem is, it neither contains the index ( 2 in screenshot) nor the unique key ( -MkqH... ).

UserData ( A class that I am using for firebaseRecyclerViewAdapter )

@Keep
@IgnoreExtraProperties
data class UserData(
    var data: UserPrefsData? = null,
    var info: UserPrefsInfo? = null
) {
    @Exclude
    fun toMap(): Map<String, Any?> {
        return mapOf(
            "data" to data,
            "info" to info
        )
    }
}

UserPrefsData

@Keep
@IgnoreExtraProperties
data class UserPrefsData(
    var color: String = BRUSH_BLACK,
    var stroke: Float = 8f,
    var data: String = "",
    var shape: Shape? = null,
    var fill: Boolean = false,
    var matrix : ArrayList<Float>? = null
) {
    @Exclude
    fun toMap(): Map<String, Any?> {
        return mapOf(
            "color" to color,
            "stroke" to stroke,
            "data" to data,
            "shape" to shape,
            "fill" to fill,
            "matrix" to matrix
        )
    }
}

UserPrefsInfo

@Keep
@IgnoreExtraProperties
data class PageInfo(
     var color: String = BRUSH_WHITE,
    var backGround: BackGround = BackGround.COLOR,
    var orientation: Int = ORIENTATION_PORTRAIT,
    var previous: Int = -1,
    var next: Int = -1
) {
    @Exclude
    fun toMap(): Map<String, Any?> {
        return mapOf(
            "color" to color,
            "backGround" to backGround,
            "orientation" to orientation,
            "previous" to previous,
            "next" to next
        )
    }
}

Activity

 private fun initFirebaseAdapter(): FirebaseAdapter? {
        val userDataRef = databaseReference.child("data")
        val options = FirebaseRecyclerOptions.Builder<UserData>()
            .setLifecycleOwner(this)
            .setQuery(userDataRef, UserData::class.java)
            .build()
        return FirebaseAdapter(
            options,
            isAdmin,
            rvItemEventListener
        )
    }

private fun setRecyclerViewAdapter(
        recyclerView: RecyclerView?,
        recyclerViewAdapter: RecyclerView.Adapter<out RecyclerView.ViewHolder>?
    ) {
        recyclerView?.adapter = recyclerViewAdapter
    }

rvFirebaseAdapter = initFirebaseAdapter()
setRecyclerViewAdapter(binding.idVRv, rvFirebaseAdapter)

FirebaseAdapter

class FirebaseAdapter(var options: FirebaseRecyclerOptions<UserData>,
                                val showDeleteOption: Boolean,
                                private val callbackListener: Callbacks.RecyclerViewItemCallback):
    FirebaseRecyclerAdapter<UserData, FirebaseAdapter.UserViewHolder>(options) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
        val itemView =
            LayoutInflater.from(parent.context).inflate(R.layout.user_item, parent, false)
        val binding = UserItemBinding.bind(itemView)
        return UserViewHolder(binding, itemView)
    }

    override fun onBindViewHolder(holder: UserViewHolder, position: Int) {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onBindViewHolder: position: $position item: ${getItem(position)} _getting data here - it is working_")
        if (position != RecyclerView.NO_POSITION) {
            bindData(holder, position)
        }
    }

    private fun bindData(holder: UserViewHolder, position: Int) {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :bindData: position: $position" _This is also working_)
        holder.binding.idVTvPageNumber.text = (position + 1).toString()
    }

    override fun getItemCount(): Int {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :superGetItemCount: ${super.getItemCount()}")
        return super.getItemCount()
    }

    inner class UserViewHolder(val binding: UserItemBinding, itemView: View): RecyclerView.ViewHolder(itemView) {
        init {
            if (showDeleteOption) {
                binding.idVIvDelete.setOnClickListener {
                    Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: UserViewHolder: :bindingAdapterPosition: $bindingAdapterPosition absoluteAdapterPosition: $absoluteAdapterPosition" _This is working_)
                    onDeleteItem(adapterPosition, binding.idVIvDelete)
                }
            } else {
                binding.idVIvDelete.visibility = View.GONE
            }
        }
    }

    private fun onDeleteItem(adapterPosition: Int, idVIvDelete: View) {
        if (adapterPosition != RecyclerView.NO_POSITION) {
            Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onDeleteItem: position: $adapterPosition" _This is also working_)
            val item = getItem(adapterPosition)
            getRef(adapterPosition).removeValue()
            callbackListener.onDeleteItem(adapterPosition, item, idVIvDelete, itemCount)
            notifyItemRemoved(adapterPosition)
        }
    }

    override fun onBindViewHolder(
        holder: UserViewHolder,
        position: Int,
        model: UserData
    ) {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onBindViewHolder: firebase: position: $position UserData: $model" _This is never being called_)
        if (position != RecyclerView.NO_POSITION) {
            bindData(holder, position)
        }
    }

    override fun onChildChanged(
        type: ChangeEventType,
        snapshot: DataSnapshot,
        newIndex: Int,
        oldIndex: Int
    ) {
        super.onChildChanged(type, snapshot, newIndex, oldIndex)
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onChildChanged: snapshot: $snapshot" _This is working_)
    }

    override fun onDataChanged() {
        super.onDataChanged()
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onDataChanged: ")
    }

    override fun onError(error: DatabaseError) {
        super.onError(error)
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :onError: $error")
    }

    override fun getItem(position: Int): UserData {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :getItem: position: $position")
        return super.getItem(position)
    }

    override fun getRef(position: Int): DatabaseReference {
        Timber.d(" :$LOG_APP_NAME: FirebaseAdapter: :getRef: position: $position")
        return super.getRef(position)
    }
}

Update: 06th Oct 2021

_The default onBindViewHolder is calling onBindViewHolder of FirebaseRecyclerAdapter and in our implementation, there was no super call. Hence, after removing onBindViewHolder(holder: UserViewHolder, position: Int) , onBindViewHolder(holder: UserViewHolder, position: Int, model: UserData) is getting called. But I still do not know how to get those indices and unique keys .

Thank you in anticipation. Any reference link, suggestion, guidance will also be helpful.

Answer 1

For such nested data, we can use a SnapshotParser . Also, in order to fulfil the requirements, I had to change data class as below:

UserData

@Keep
@IgnoreExtraProperties
data class UserData(

    @Exclude
    var dataIndex: Long? = null,

    @Exclude
    var userDataItemKey: String? = null,

    @Exclude
    var listOfUserPrefsData: MutableList<UserPrefsData?>? = null,

    @JvmField
    @PropertyName(AppFirebase.DATA)
    var data: UserPrefsData? = null,

    @JvmField
    @PropertyName(AppFirebase.INFO)
    var userPrefsInfo: UserPrefsInfo? = null
) {
    @Exclude
    fun toMap(): Map<String, Any?> {
        return mapOf(
            "data" to data,
            "info" to userPrefsInfo
        )
    }
}

After that, I have used SnapshotParser as below:

private fun initFirebaseAdapter(): FirebaseAdapter? {
        val userDataRef = databaseReference.child(AppFirebase.DATA)
        val options = FirebaseRecyclerOptions.Builder<UserData>()
            .setLifecycleOwner(this)
            .setQuery(userDataRef) {
                val userPrefsInfo: UserPrefsInfo?
                var userDataItemKey: String? = null
                val listOfUserPrefsData = mutableListOf<UserPrefsData?>()
                val dataIndex = it.key?.toLong()
                val userPrefsInfoRef = it.child(AppFirebase.INFO)
                userPrefsInfo = userPrefsInfoRef.getValue<UserPrefsInfo>()
                val userPrefsDataRef = it.child(AppFirebase.DATA)
                for (userDataItem in userPrefsDataRef.children) {
                    userDataItemKey = userDataItem.key
                    val userPrefsData = userDataItem.getValue<UserPrefsData>()
                    userPrefsData?.userDataItemKey = userDataItemKey
                    listOfUserPrefsData.add(userPrefsData)
                }
                UserData(
                    dataIndex = dataIndex,
                    userDataItemKey = userDataItemKey,
                    listOfUserPrefsData = listOfUserPrefsData,
                    userPrefsInfo = userPrefsInfo
                )
            }
            .build()
        return FirebaseAdapter(
            options,
            isAdmin,
            rvWhiteboardItemEventListener
        )
    }

Now I have that 2 indices, that list of -Mkq... unique keys including UserPrefsData and UserPrefsInfo for each index. So, basically, everything that is there under data of 6154... including indices and unique keys...