為什么RecyclerView在其余KotlinAndroid之前加載-有解無憂

您好，我正在為我的家庭作業做一個小應用程式，我想在應用程式上顯示來自我的 php api 的資料。但是 Recycler View2022-04-25 00:41:36.662 13593-13593/net.robcorp.finalapp E/RecyclerView: No adapter attached; skipping layout在配接器代碼運行之前發送此訊息，因為此訊息2022-04-25 00:41:36.907 13593-13593/net.robcorp.finalapp I/System.out: [Drivers(pos=1, name=Charles Leclerc, nb=16, points=71, title=Ferrari), Drivers(pos=2, name=Esteban Ocon, nb=31, points=20, title=Alpine)]顯示在前一個訊息之后，并且假設在配接器之前運行。這是 DriversFragment.kt：

package net.robcorp.finalapp

import android.content.Context
import android.graphics.Insets.add
import android.os.Bundle
import android.util.Log
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.view.OneShotPreDrawListener.add
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.Observer
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.android.volley.Request
import com.android.volley.Response
import com.android.volley.toolbox.StringRequest
import com.android.volley.toolbox.Volley
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.FragmentDriversBinding
import net.robcorp.finalapp.drivers.DriverFragmentAdapter
import net.robcorp.finalapp.drivers.Drivers
import org.json.JSONArray


class DriversFragment : Fragment(R.layout.fragment_drivers) {

    private lateinit var recyclerView: RecyclerView
    private lateinit var myAdapter: DriverFragmentAdapter;
    lateinit var binding: FragmentDriversBinding
    private val drivers = ArrayList<Drivers>()
    val url = "https://robcorp.net/f1api/getdrivers.php"

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        binding = FragmentDriversBinding.inflate(layoutInflater)
        recyclerView = binding.driversRecyclerView
        recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)
        myAdapter = DriverFragmentAdapter(drivers)
        recyclerView.adapter = myAdapter
        println("adapter loaded")
        downloadDrivers()
    }

    fun downloadDrivers() {
        val task = Volley.newRequestQueue(this.context)
        val request = StringRequest(Request.Method.GET, url, {
                response ->
            val data = response.toString()
            val jArray = JSONArray(data)
//            Log.e("Error",response.toString())
            for (i in 0..jArray.length()-1) {
                val json_data = jArray.getJSONObject(i)
//                Log.e("Jobject",json_data.toString())
                val pos = i 1
                val name = json_data.getString("Name")
                val nb = json_data.getString("NB")
                val points = json_data.getString("Points")
                val title = json_data.getString("Title")
                val driver = Drivers(pos, name, nb, points, title)
                drivers.add(driver)

            }
            println(drivers)
            myAdapter.notifyDataSetChanged()
        }, {
                error ->
            println(error)
        })
        task.add(request)
    }
}

這是 DriverFragmentAdapter.kt：

package net.robcorp.finalapp.drivers

import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.RecyclerView
import net.robcorp.finalapp.R
import net.robcorp.finalapp.databinding.DriverListBinding

class DriverFragmentAdapter(private var driversList: List<Drivers>): RecyclerView.Adapter<DriverFragmentAdapter.MyViewHolder>() {

    class MyViewHolder(val binding: DriverListBinding) : RecyclerView.ViewHolder(binding.root) {
        fun bind(driver: Drivers) {
            val context = itemView.context
            val pos = itemView.findViewById<TextView>(R.id.driver_position)
            val bar = itemView.findViewById<TextView>(R.id.driver_bar)
            val name = itemView.findViewById<TextView>(R.id.driver_name)
            val nb = itemView.findViewById<TextView>(R.id.driver_number)
            val team = itemView.findViewById<TextView>(R.id.driver_team)
            val points = itemView.findViewById<TextView>(R.id.driver_points)

            pos.text = driver.pos.toString()
            name.text = driver.name
            nb.text = driver.nb
            team.text = driver.title
            points.text = driver.points

            if (driver.title == "Ferrari") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.ferrari_bar)
            } else if (driver.title == "Alpine") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.alpine_bar)
            } else if (driver.title == "Red Bull") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.redbull_bar)
            } else if (driver.title == "Mercedes") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.mercedes_bar)
            } else if (driver.title == "McLaren") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.mclaren_bar)
            } else if (driver.title == "Alfa Romeo") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.alfaromeo_bar)
            } else if (driver.title == "AlphaTauri") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.alphatauri_bar)
            } else if (driver.title == "Williams") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.williams_bar)
            } else if (driver.title == "Aston Martin") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.astonmartin_bar)
            } else if (driver.title == "Haas") {
                bar.background = ContextCompat.getDrawable(context, R.drawable.haas_bar)
            }
        }
    }
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        return MyViewHolder(DriverListBinding.inflate(LayoutInflater.from(parent.context)))

    }

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

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        val driver = driversList[position]
        holder.binding.apply {
            println("je suis dans le binding")
            holder.bind(driver)
        }
    }

    fun setDriversList(driversList: List<Drivers>) {
        this.driversList = driversList
        notifyDataSetChanged()
    }

}

片段驅動程式.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

    <!-- TODO: Update blank fragment layout -->
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <LinearLayout
            android:id="@ id/header"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/primary"
            android:orientation="vertical"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_marginBottom="10dp">

            <TextView
                android:id="@ id/calendar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="30dp"
                android:layout_marginTop="20dp"
                android:layout_marginEnd="30dp"
                android:layout_marginBottom="20dp"
                android:fontFamily="@font/marianneb"
                android:text="Pilotes"
                android:textAlignment="center"
                android:textColor="@color/white"
                android:textSize="25sp" />

        </LinearLayout>

        <androidx.recyclerview.widget.RecyclerView
            android:id="@ id/drivers_recycler_view"
            android:scrollbars="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintTop_toBottomOf="@ id/header"/>

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

driver_list.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"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginStart="20dp"
    android:layout_marginTop="10dp"
    android:layout_marginEnd="20dp"
    android:elevation="8dp"
    android:orientation="horizontal"
    android:padding="10dp"
    android:background="@drawable/rectangle">

    <TextView
        android:id="@ id/driver_position"
        android:layout_width="30dp"
        android:layout_height="match_parent"
        android:fontFamily="@font/marianneb"
        android:text="1"
        android:textColor="@color/black"
        android:textSize="25sp"
        android:textAlignment="center"/>

    <ImageView
        android:id="@ id/driver_bar"
        android:layout_width="20px"
        android:layout_height="match_parent"
        android:background="@drawable/ferrari_bar"/>



    <LinearLayout
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@ id/driver_name"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:fontFamily="@font/marianneb"
            android:text="Charles Leclerc"
            android:textColor="@color/black"
            android:textSize="15sp"
            android:layout_marginStart="10dp"/>

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

            <TextView
                android:id="@ id/driver_number"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="10dp"
                android:layout_marginTop="2.5dp"
                android:fontFamily="@font/mariannem"
                android:text="16"
                android:textColor="@color/black"
                android:textSize="10sp" />

            <TextView
                android:id="@ id/driver_team"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="10dp"
                android:layout_marginTop="2.5dp"
                android:fontFamily="@font/mariannem"
                android:text="Ferrari"
                android:textColor="@color/black"
                android:textSize="10sp" />

        </LinearLayout>

    </LinearLayout>

    <TextView
        android:id="@ id/driver_points"
        android:layout_width="50dp"
        android:layout_height="match_parent"
        android:fontFamily="@font/marianneb"
        android:text="578"
        android:textColor="@color/black"
        android:textSize="25sp"/>



</LinearLayout>

uj5u.com熱心網友回復：

這是一個無害的警告。由于您的 RecyclerView 已經在布局中，它會在您的視圖層次結構變得可見時嘗試繪制它，發現沒有分配配接器，因此它只是發出警告而不繪制它。

也許創建您的配接器（帶有一個空串列）并在擴展視圖時立即分配它會更干凈，并在資料準備好時更新其串列。

順便說一句，在onCreate. 那應該在onCreateView.

編輯：

您在此處的代碼將布局膨脹兩次，一次用于變數v，一次用于binding屬性。首先，沒有理由給它充氣兩次。其次，由于您使用v的回傳值onCreateView，因此您對中的視圖所做的任何事情binding都是沒有意義的，并且對實際在螢屏上的視圖沒有影響。

    val v = inflater.inflate(R.layout.fragment_drivers, container, false)
    binding = FragmentDriversBinding.inflate(layoutInflater)
    // ...
    return v

您應該只膨脹一次視圖（使用系結）并回傳系結的視圖：

    // DELETE THIS LINE: val v = inflater.inflate(R.layout.fragment_drivers, container, false)
    binding = FragmentDriversBinding.inflate(layoutInflater)
    // ...
    return binding.root

onViewCreated()此外，將視圖設定在 in而不是 in更合適onCreateView()。如果你這樣做了，你實際上可以通過將視圖 ID 傳遞給 Fragment 建構式來將膨脹移動到超級建構式呼叫中，然后系結到現有視圖而不是膨脹你的系結。它看起來像這樣：

class DriversFragment : Fragment(R.layout.fragment_drivers) {

    private lateinit var recyclerView: RecyclerView
    private lateinit var myAdapter: DriverFragmentAdapter;
    lateinit var binding: FragmentDriversBinding
    private val drivers = ArrayList<Drivers>()
    val url = "https://robcorp.net/f1api/getdrivers.php"

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        binding = FragmentDriversBinding.bind(view)
        recyclerView = binding.driversRecyclerView

        recyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)

        myAdapter = DriverFragmentAdapter(drivers)

        recyclerView.adapter = myAdapter
        println("adapter loaded")
        downloadDrivers()
    }

    //...
}

uj5u.com熱心網友回復：

為@Tenfour04 的答案增加一點清晰度。

你不能洗掉這個。他們告訴你如何用視圖系結正確地膨脹它

override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
): View? {
    binding = FragmentDriversBinding.inflate(layoutInflater, container, false)
    return binding.root
}

還有一點旁注：

您應該像這樣銷毀您的系結以防止記憶體泄漏

override fun onDestroyView() {
    super.onDestroyView()
    binding = null
}

現在的問題。

  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        //binding = FragmentDriversBinding.bind(view) this is not needed since its already been inflated
        //recyclerView = binding.driversRecyclerView why keep recyclerview as another variable when you can access it with binding.driversRecyclerView?

        binding.driversRecyclerView.layoutManager = LinearLayoutManager(activity, LinearLayoutManager.VERTICAL, false)

        myAdapter = DriverFragmentAdapter(drivers)

        binding.driversRecyclerView.adapter = myAdapter
        println("adapter loaded")
        downloadDrivers()
    }

最后，問題很可能是您的布局。由于所有內容都包含在線性布局中，因此約束布局位置線不做任何事情。我洗掉了無用的線性布局。希望這可以解決任何問題。

抱歉格式化順便說一句，只需使用 CTRL ALT L 自動格式化

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".MainActivity">

            <LinearLayout
            android:id="@ id/header"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/primary"
            android:orientation="vertical"
            app:layout_constraintTop_toTopOf="parent"
            android:layout_marginBottom="10dp">

            <TextView
                android:id="@ id/calendar"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="30dp"
                android:layout_marginTop="20dp"
                android:layout_marginEnd="30dp"
                android:layout_marginBottom="20dp"
                android:fontFamily="@font/marianneb"
                android:text="Pilotes"
                android:textAlignment="center"
                android:textColor="@color/white"
                android:textSize="25sp" />

        </LinearLayout>

         <androidx.recyclerview.widget.RecyclerView
            android:id="@ id/drivers_recycler_view"
            android:scrollbars="vertical"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintTop_toBottomOf="@ id/header"/>

</androidx.constraintlayout.widget.ConstraintLayout>

轉載請註明出處，本文鏈接：https://www.uj5u.com/qukuanlian/465054.html

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