How to attach an adapter in fragment? - kotlin

Question

I use Kotlin in SDK 29.
I would like to make a recyclerView in my fragment. When I run the device, it doesn't crash, the fragment appear but not the Recycler View and I have the following error :
E/RecyclerView: No adapter attached; skipping layout
Here is my code :
Adapter
Import :
import android.content.Context
import android.text.format.DateUtils
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.example.givenaskv1.R
import kotlinx.android.synthetic.main.item_post.view.*
Code :
class PostsAdapter (val context: Context, val posts : List<Post>) :
RecyclerView.Adapter<PostsAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(context).inflate(R.layout.item_post, parent, false)
return ViewHolder(view)
}
override fun getItemCount() = posts.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.bind(posts[position])
}
inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
fun bind(post: Post) {
itemView.tvUsername.text = post.user?.firstName
itemView.tvDescription.text = post.description
Glide.with(context).load(post.imageUrl).into(itemView.ivPost)
itemView.tvRelativeTime.text = DateUtils.getRelativeTimeSpanString(post.creationTimeMs)
}
}
}
Fragment
Import :
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.givenaskv1.R
import com.example.givenaskv1.models.Post
import com.example.givenaskv1.models.PostsAdapter
import com.google.firebase.firestore.FirebaseFirestore
import com.google.firebase.firestore.Query
import kotlinx.android.synthetic.main.fragment_flux.*
Code :
private const val TAG = "Flux"
#Suppress("UNREACHABLE_CODE")
class Flux : Fragment() {
private lateinit var firestoreDb : FirebaseFirestore
private lateinit var posts : MutableList<Post>
private lateinit var adapter: PostsAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_flux, container, false)
posts = mutableListOf()
adapter = PostsAdapter(requireContext(), posts)
rvPosts.adapter = adapter
rvPosts.layoutManager = LinearLayoutManager(requireContext())
firestoreDb = FirebaseFirestore.getInstance()
val postsReference = firestoreDb.collection("post")
// .limit() indique le nombre de post MAXIMIM a afficher en même temps, pour éviter le lagg
.limit(20)
// .orderBy() filtre selon le critère choisi (ici par ordre chonologique)
.orderBy("creation_time_ms", Query.Direction.DESCENDING)
postsReference.addSnapshotListener{ snapshot, exception ->
if (exception != null || snapshot == null) {
Log.e(TAG, "Exception when querying posts", exception)
return#addSnapshotListener
}
val postList = snapshot.toObjects(Post::class.java)
posts.clear()
posts.addAll(postList)
adapter.notifyDataSetChanged()
for (post in postList) {
Log.i(TAG, "Post ${post}")
}
}
}
Fragment.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".Flux.Flux">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvPosts"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
android:orientation="vertical"
/>
</LinearLayout>
Can you please help me ? Thank you !

Answer 1

You should return view at the end of onCreateView
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
val view = inflater.inflate(R.layout.fragment_flux, container, false)
posts = mutableListOf()
adapter = PostsAdapter(requireContext(), posts)
rvPosts = view.findViewById<RecyclerView>(R.id.rvPosts)
rvPosts.layoutManager = LinearLayoutManager(requireContext())
rvPosts.adapter = adapter
firestoreDb = FirebaseFirestore.getInstance()
val postsReference = firestoreDb.collection("post")
// .limit() indique le nombre de post MAXIMIM a afficher en même temps, pour éviter le lagg
.limit(20)
// .orderBy() filtre selon le critère choisi (ici par ordre chonologique)
.orderBy("creation_time_ms", Query.Direction.DESCENDING)
postsReference.addSnapshotListener{ snapshot, exception ->
if (exception != null || snapshot == null) {
Log.e(TAG, "Exception when querying posts", exception)
return#addSnapshotListener
}
val postList = snapshot.toObjects(Post::class.java)
posts.clear()
posts.addAll(postList)
adapter.notifyDataSetChanged()
for (post in postList) {
Log.i(TAG, "Post ${post}")
}
}
return view
}