如何將資料從配接器傳遞到片段？

我一直在嘗試將資料（用戶的電子郵件和電話）從我的配接器傳遞到我的片段。根據我在網上閱讀的內容，我應該為此使用一個界面，但我仍然無法將資料放入我的片段中。任何人都可以逐步解釋我應該如何添加介面以及如何將資料從我的配接器放入我的介面，以便我可以在我的片段中呼叫它。或者是否有另一種方法可以將資料從我的配接器傳遞到我的片段。下面是我的配接器和我的片段。

配接器：

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

}

}

分段

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")
        }

    })

}

}

uj5u.com熱心網友回復：

如果你想使用一個介面，你只需要定義一個函式來接收你的資料，讓片段實作它，然后將片段作為該介面的實作傳遞給配接器：

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)
    }
}

然后在片段中：

// 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
    }
}

就是這樣。您沒有硬編碼對該特定 Fragment 型別的依賴項，只是對介面進行了硬編碼，并且此 Fragment 實作了它，因此它可以自行傳遞。

一種更 Kotliny 的方法是忽略介面并只傳遞一個函式

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
    }
}

理想情況下，您應該做我在那里所做的事情 - 在設定期間創建一次配接器，并在其上具有允許您更新它的功能。每次獲取資料時，您的代碼都會創建一個新代碼。你在這兩種方法中都這樣做

您的另一個選擇是使用配接器和片段都可以訪問的視圖模型，但這是您執行介面/回呼方法的方式

uj5u.com熱心網友回復：

實際上，有一種非常簡單的方法可以將資料從配接器獲取到片段或活動中。它使用高階函式呼叫。 在您的配接器中在您的配接器 中添加高階函式。

class UserAdapter(private val userList: ArrayList<UserModel>, val context: Context) :
RecyclerView.Adapter<UserAdapter.UserViewHolder>() {
//your rest of the adapter's code

private var onItemClickListener:((UserModel)->Unit)? = null
fun setOnItemClickListener(listener: (UserModel)->Unit) {
     onItemClickListener = listener
   }
}

在您的 UserViewHolder 中

val rootView = itemView.rootView

在您的 onBindViewHolder中，在 rootView 上設定一個點擊監聽器

holder.rootView.setOnClickListener {
   onItemClickListener?.let{
          it(currentItem)
    }
}

在你的片段中

//create the instance of UserAdapter
userAdapter.setOnItemClickListener {
  //here you have your UserModel in your fragment, do whatever you want to with it
}

并且，在最后一個建議。開始使用 ViewBinding，它將使您免于繁重的作業。

標籤：安卓 科特林 安卓片段 android-recyclerview 安卓适配器

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