Как из Firebase добавить данные в RecyclerView

Question

Столкнулся с такой проблемой! Делаю приложение и сейчас мне нужно добавить два разных recyclerview в разные активити. Данные берутся из Firebase.

На первое активити я сделал - все ок. Данные отображаются как нужно, а вот на втором проблема. Мне нужно добавить другие данные, но ошибка java.lang.NullPointerException: workout_title must not be null Знаю, что нужно их инициализировать, но можете подсказать как правильно это сделать и реализовать в проекте?

Код: HomeActivity

package com.skreep.worko

import android.os.Bundle
import android.widget.Toast
import androidx.recyclerview.widget.LinearLayoutManager
import com.google.firebase.database.*
import com.skreep.worko.adapter.WorkoutAdapter
import com.skreep.worko.model.WorkoutData
import kotlinx.android.synthetic.main.activity_detail.*
import kotlinx.android.synthetic.main.activity_home.*


class HomeActivity : BaseActivity() {

    lateinit var mDataBase: DatabaseReference
    private lateinit var workoutList: ArrayList<WorkoutData>
    private lateinit var mAdapter: WorkoutAdapter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_home)

        workoutList = ArrayList()
        mAdapter = WorkoutAdapter(this, workoutList)

        recyclerworkoutList.layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
        recyclerworkoutList.setHasFixedSize(true)

        recyclerworkoutList.adapter = mAdapter


        getWorkoutData()

    }

    private fun getWorkoutData() {

        mDataBase = FirebaseDatabase.getInstance().getReference("Workout")

        mDataBase.addValueEventListener(object : ValueEventListener {

            override fun onDataChange(snapshot: DataSnapshot) {

                if (snapshot.exists()) {

                    for (userSnapshot in snapshot.children) {

                        val workout = userSnapshot.getValue(WorkoutData::class.java)
                        workoutList.add(workout!!)

                    }

                    recyclerworkoutList.adapter = mAdapter


                }


            }

            override fun onCancelled(error: DatabaseError) {
                Toast.makeText(this@HomeActivity,
                        error.message, Toast.LENGTH_SHORT).show()
            }

        })
    }


}

DetailActivity

package com.skreep.worko



import android.content.Intent
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_detail.*
import kotlinx.android.synthetic.main.item_workout_detail.*

class DetailActivity() : BaseActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_detail)


        val workoutIntent = intent
        val name = workoutIntent.getStringExtra("name")
        val description = workoutIntent.getStringExtra("description")
        val workoutName = workoutIntent.getStringExtra("workoutName")


        detail_name.text = name
        detail_desc.text = description
        workout_title.text = workoutName






        back_ic.setOnClickListener {
            val intent = Intent(this, HomeActivity::class.java)
            startActivity(intent)
        }

    }


}

Adapter

package com.skreep.worko.adapter

import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.recyclerview.widget.RecyclerView
import com.skreep.worko.DetailActivity
import com.skreep.worko.R
import com.skreep.worko.databinding.ItemWorkoutBinding
import com.skreep.worko.databinding.ItemWorkoutDetailBinding
import com.skreep.worko.model.WorkoutData

class WorkoutAdapter(var c: Context, var workoutList: ArrayList<WorkoutData>
) : RecyclerView.Adapter<WorkoutAdapter.WorkoutViewHolder>() {
    inner class WorkoutViewHolder(var v: ItemWorkoutBinding) : RecyclerView.ViewHolder(v.root) {}


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WorkoutViewHolder {
        val inflter = LayoutInflater.from(parent.context)
        val v = DataBindingUtil.inflate<ItemWorkoutBinding>(
                inflter, R.layout.item_workout, parent,
                false)

        return WorkoutViewHolder(v)


    }

    override fun onBindViewHolder(holder: WorkoutViewHolder, position: Int) {
        val newList = workoutList[position]
        holder.v.isWorkouts = workoutList[position]



        holder.v.root.setOnClickListener {
            val name = newList.name
            val description = newList.description
            val fullTime = newList.fullTime
            val workoutDesc = newList.workoutDesc
            val workoutName = newList.workoutName
            val workoutTime = newList.workoutTime


            val mIntent = Intent(c, DetailActivity::class.java)
            mIntent.putExtra("description", description)
            mIntent.putExtra("name", name)
            mIntent.putExtra("fullTime", fullTime)
            mIntent.putExtra("workoutDesc", workoutDesc)
            mIntent.putExtra("workoutName", workoutName)
            mIntent.putExtra("workoutTime", workoutTime)
            c.startActivity(mIntent)
        }
    }


    override fun getItemCount(): Int {
        return workoutList.size
    }


}

xml home
<?xml version="1.0" encoding="utf-8"?>

<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <variable
            name="isWorkouts"
            type="com.skreep.worko.model.WorkoutData" />


    </data>

    <RelativeLayout
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/darkblue"
        android:orientation="vertical"
        tools:context=".HomeActivity">


        <ScrollView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:scrollbars="none">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical">

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_margin="20dp"
                    android:fontFamily="@font/poppins"
                    android:gravity="center"
                    android:padding="20dp"
                    android:text="@string/app_name"
                    android:textColor="@color/white"
                    android:textSize="20sp" />


                <TextView
                    android:id="@+id/welcome"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:fontFamily="@font/poppins"
                    android:paddingLeft="20dp"
                    android:paddingTop="10dp"
                    android:text="@string/welcome"
                    android:textColor="@color/white"
                    android:textSize="30sp"
                    tools:ignore="MissingConstraints" />


                <TextView
                    android:id="@+id/welcome_description"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:fontFamily="@font/poppins"
                    android:paddingLeft="20dp"
                    android:paddingTop="10dp"
                    android:text="@string/welcome_description"
                    android:textColor="@color/desc_color"
                    android:textSize="14sp"
                    app:layout_constraintTop_toBottomOf="@id/welcome" />


                <androidx.recyclerview.widget.RecyclerView
                    android:id="@+id/recyclerworkoutList"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"
                    android:orientation="horizontal"
                    android:paddingTop="40dp"
                    tools:itemCount="1"
                    tools:listitem="@layout/item_workout" />

            </LinearLayout>
        </ScrollView>


    </RelativeLayout>
</layout>

xml detail

<?xml version="1.0" encoding="utf-8"?>

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable
            name="isWorkout"
            type="com.skreep.worko.model.WorkoutData" />


    </data>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/gray"
        tools:context=".DetailActivity">


        <ImageView
            android:id="@+id/back_ic"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_margin="20dp"
            android:padding="20dp"
            android:src="@drawable/ic_back">

        </ImageView>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_margin="20dp"
            android:fontFamily="@font/poppins"
            android:padding="20dp"
            android:text="@string/app_name"
            android:textSize="20sp"></TextView>

        <TextView
            android:id="@+id/detail_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="30dp"
            android:layout_marginTop="120dp"
            android:fontFamily="@font/poppins_bold"
            android:text="@{isWorkout.name}"
            android:textColor="@color/darkblue"
            android:textSize="26sp"></TextView>


        <TextView
            android:id="@+id/detail_desc"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/detail_name"
            android:layout_alignLeft="@+id/detail_name"
            android:fontFamily="@font/poppins"
            android:text="@{isWorkout.workoutDesc}"
            android:textColor="@color/lightgray">

        </TextView>

        <TextView
            android:id="@+id/tv_workout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="310dp"
            android:fontFamily="@font/poppins_bold"
            android:gravity="center"
            android:text="Упражнения"
            android:textColor="@color/darkblue"
            android:textSize="20sp"></TextView>


        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

        </LinearLayout>



        <androidx.recyclerview.widget.RecyclerView

            android:id="@+id/rv_detail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@+id/tv_workout"
            android:orientation="vertical"
            android:padding="10dp"
            tools:itemCount="1"
            tools:listitem="@layout/item_workout_detail"
            >


        </androidx.recyclerview.widget.RecyclerView>
        
        


    </RelativeLayout>
</layout>

Answer 1

В моём случае так:

User class

data class User(
val fullName: String? = null,
val email: String? = null )

Adapter

class MyAdapter(var list: ArrayList<User>): RecyclerView.Adapter<MyAdapter.MyViewHolder>() {

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
    return MyViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.read_item, parent, false))
}

override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
    val currentUser = list[position]

    with(holder.itemView) {
        get_Fullname_tv.text = currentUser.fullName
        get_Email_tv.text = currentUser.email

    }
}

override fun getItemCount(): Int {
    return list.size
}

class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

}

MainActivity

// поля

private lateinit var database: FirebaseDatabase
private lateinit var mRef: DatabaseReference

//метод для получения данных в RecyclerView. (При клике на кнопку)

database = FirebaseDatabase.getInstance()
mRef = database.getReference("Users")

getData_button.setOnClickListener {
        val postListener = object : ValueEventListener{
            override fun onDataChange(snapshot: DataSnapshot) {
                val list = ArrayList<User>()
                for (ds in snapshot.children){
                    val user = ds.getValue(User::class.java)
                    list.add(user as User)
                }
                if (list.size > 0) {
                    val adapter = MyAdapter(list)
                    recyclerView.adapter = adapter
                    recyclerView.layoutManager = LinearLayoutManager(applicationContext)
                }
            }

            override fun onCancelled(error: DatabaseError) {
                Log.d("ValEvenLisLog", error.toString())
            }
        }
        mRef.addValueEventListener(postListener)
    }

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Как из Firebase добавить данные в RecyclerView

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