I've been trying to pass data(the email and phone of a user) from my adapter to my fragment. From what I've read online I should use a interface for this but I cant the data into my fragment still. Can anyone explain in steps how I should add a interface and how to put data into my interface from my adapter so I can call it in my fragment. Or is there another way to pass data from my adapter to my fragment. Below are my adapter and my fragment.
Adapter:
package ie.wit.savvytutor.adapters
import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import ie.wit.savvytutor.R
import ie.wit.savvytutor.activity.MainActivity
import ie.wit.savvytutor.fragments.ViewChatFragment
import ie.wit.savvytutor.models.UserModel
class UserAdapter(private val userList: ArrayList<UserModel>, val context: Context) :
RecyclerView.Adapter<UserAdapter.UserViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
val itemView =
LayoutInflater.from(parent.context).inflate(R.layout.user_layout, parent, false)
return UserViewHolder(itemView)
}
class UserViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val username: TextView = itemView.findViewById(R.id.userNameView)
}
override fun onBindViewHolder(holder: UserViewHolder, position: Int, ) {
val currentItem = userList[position]
holder.username.text = currentItem.email
holder.itemView.setOnClickListener {
println(currentItem)
val optionsFrag = ViewChatFragment()
(context as MainActivity).getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_container, optionsFrag, "OptionsFragment").addToBackStack(
null
)
.commit()
}
}
override fun getItemCount(): Int {
return userList.size
}
}
Fragment
package ie.wit.savvytutor.fragments
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.annotation.Nullable
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.database.*
import ie.wit.savvytutor.R
import ie.wit.savvytutor.adapters.UserAdapter
import ie.wit.savvytutor.models.UserModel
class TutorChatFragment : Fragment() {
private lateinit var userRecyclerView: RecyclerView
private lateinit var userArrayList: ArrayList<UserModel>
private lateinit var dbRef: DatabaseReference
private lateinit var mAuth: FirebaseAuth
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
dbRef = FirebaseDatabase.getInstance("DATABASE LINK").getReference("Users").ref
mAuth = FirebaseAuth.getInstance()
}
@Nullable
override fun onCreateView(
inflater: LayoutInflater,
@Nullable container: ViewGroup?,
@Nullable savedInstanceState: Bundle?
): View {
//inflate the fragment layout
val root = inflater.inflate(R.layout.tutor_chat_fragment, container, false)
userRecyclerView = root.findViewById(R.id.userListView)
userRecyclerView.layoutManager = LinearLayoutManager(context)
userRecyclerView.setHasFixedSize(true)
userArrayList = arrayListOf<UserModel>()
getUser()
return root
}
private fun getUser() {
userArrayList.clear()
dbRef.addValueEventListener(object: ValueEventListener{
override fun onDataChange(snapshot: DataSnapshot) {
for (postSnapshot in snapshot.children) {
val currentUser = postSnapshot.getValue(UserModel::class.java)
//BUG FIX 1.26.13
val email = currentUser?.email
if (email != null) {
userArrayList.add(currentUser)
}
userRecyclerView.adapter?.notifyDataSetChanged()
userRecyclerView.adapter = context?.let { UserAdapter(userArrayList, it) }
}
}
override fun onCancelled(error: DatabaseError) {
TODO("Not yet implemented")
}
})
}
}
If you want to use an interface, you just need to define one with a function to receive your data, make the fragment implement it, then pass the fragment to the adapter as an implementation of that interface:
data class UserData(val email: String, val phone: String)
class UserAdapter(
private val userList: ArrayList<UserModel>,
val context: Context,
val handler: UserAdapter.Callbacks // added this here, so you're passing it in at construction
) : RecyclerView.Adapter<UserAdapter.UserViewHolder>() {
...
private fun doWhatever(email: String, phone: String) {
// pass the data to the handler (which will probably be your Fragment)
handler.handleUserData(UserData(email, phone))
}
// nested inside the UserAdapter class to keep things tidy
interface Callbacks {
fun handleUserData(data: UserData)
}
}
Then in the Fragment:
// add the Callbacks interface type
class TutorChatFragment : Fragment(), UserAdapter.Callbacks {
override fun onCreateView(
inflater: LayoutInflater,
@Nullable container: ViewGroup?,
@Nullable savedInstanceState: Bundle?
): View {
...
userRecyclerView.layoutManager = LinearLayoutManager(context)
// set up the adapter here, passing this fragment as the Callbacks handler
userRecyclerView.adapter = UserAdapter(userArrayList, context, this)
...
}
// interface implementation
override fun handleUserData(data: UserData) {
// whatever
}
}
And that's it. You're not hardcoding a dependency on that particular Fragment type, just the interface, and this fragment implements it so it can pass itself.
A more Kotliny way to do it is to ignore interfaces and just pass a function instead
class UserAdapter(
private val userList: ArrayList<UserModel>,
val context: Context,
val handler: (UserData) -> Unit // passing a function that takes a UserData instead
) : RecyclerView.Adapter<UserAdapter.UserViewHolder>() {
...
private fun doWhatever(email: String, phone: String) {
// call the handler function with your data (you can write handler.invoke() if you prefer)
handler(UserData(email, phone))
}
}
// no interface this time
class TutorChatFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
@Nullable container: ViewGroup?,
@Nullable savedInstanceState: Bundle?
): View {
...
userRecyclerView.layoutManager = LinearLayoutManager(context)
// pass in a handler function
userRecyclerView.adapter = UserAdapter(userArrayList, context) { userData ->
handleUserData(userData)
}
// or if you're just passing it to that function down there,
// you could do UserAdapter(userArrayList, context, ::handleUserData)
// and pass the function reference
...
}
// might be convenient to still do this in its own function
private fun handleUserData(data: UserData) {
// whatever
}
}
Ideally you should be doing what I've done there - create the adapter once during setup, and have a function on it that allows you to update it. Your code creates a new one each time you get data. You do this the same way in both though
Your other option is using a view model that the adapter and fragment both have access to, but this is how you do the interface/callback approach