RecyclerView 没有 LayoutManager |科特林

Question

我正在尝试在 RecyclerView 中创建一个 CardView，但我无法启动它，因为应用程序在出现此错误“RecyclerView 没有 LayoutManager”后崩溃。我已尝试应用其他帖子建议的有关同一问题的修复，但到目前为止没有运气。

提前谢谢你。

HomeActivity.kt

class HomeActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_home)

    // Retrieves data from source
    val arrayList = ArrayList<PreviewCardModel>()
    arrayList.add(PreviewCardModel("Product A","500mg / 1000mg", R.drawable.image, 500))
            arrayList.add(PreviewCardModel("Product D","Sample", R.drawable.image, 5040))
            arrayList.add(PreviewCardModel("Product E","Sample", R.drawable.image, 5500))
            arrayList.add(PreviewCardModel("Product F","Sample", R.drawable.image, 2500))

    val myAdapter = CardAdapter(arrayList, this)
    recyclerView.layoutManager = LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL,false)
    recyclerView.adapter = myAdapter

CardAdapter.kt

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.sample.appname.R
import com.sample.appname.model.PreviewCardModel
import kotlinx.android.synthetic.main.preview_card.view.*

class CardAdapter (private val arrayList: ArrayList<PreviewCardModel>, val context: Context) :
    RecyclerView.Adapter<CardAdapter.CardViewHolder>() {

    class CardViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        fun bindItems (model: PreviewCardModel) {
            itemView.previewName.text = model.title
            itemView.previewDesc.text = model.desc
            itemView.previewPrice.text = model.price.toString()
            itemView.previewImage.setImageResource(model.image)
        }
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CardViewHolder {

        val view = LayoutInflater.from(parent.context).inflate(R.layout.preview_card, parent, false)

        return CardViewHolder(view)
    }

    // Returns size of data list
    override fun getItemCount(): Int {
        return arrayList.size
    }
    // Displays data at a certain position
    override fun onBindViewHolder(holder: CardViewHolder, position: Int) {
        holder.bindItems(arrayList[position])
        }
    }

activity_home.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"
    android:padding="16dp"
    tools:context=".HomeActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:background="@color/browser_actions_title_color"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:orientation="horizontal"
        />
</androidx.constraintlayout.widget.ConstraintLayout>

这是我遇到的错误。

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.sample.appname, PID: 5333
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sample.appname/com.sample.appname.HomeActivity}: android.view.InflateException: Binary XML file line #54 in com.sample.appname:layout/activity_home: RecyclerView has no LayoutManager androidx.recyclerview.widget.RecyclerView{b2c2d71 VFED..... ......I. 0,0-0,0 #7f09016f app:id/recyclerView}, adapter:null, layout:null, context:com.sample.appname.HomeActivity@5dcb507

preview_card.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="wrap_content"
    android:layout_height="120dp"
    android:padding="10sp"
    app:cardCornerRadius="3dp"
    app:cardElevation="3dp"
    app:cardUseCompatPadding="true">

        <ImageView
            android:id="@+id/previewImage"
            android:layout_width="80dp"
            android:layout_height="80dp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            android:src="@drawable/heart"
            android:contentDescription="@string/product_image" />

        <TextView
            android:id="@+id/previewName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/product_name"
            android:textSize="11sp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/previewImage" />

        <TextView
            android:id="@+id/previewDesc"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="SAMPLE"
            android:textSize="8sp"
            android:textColor="@color/colorPrimary"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/previewName"
            tools:ignore="SmallSp" />

        <TextView
            android:id="@+id/previewPrice"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:text="@string/samplePrice"
            android:textColor="@color/colorPrimary"
            android:textSize="11sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintBottom_toBottomOf="parent" />

</androidx.cardview.widget.CardView>

Answer 1

当您为多个 SDK 或方向创建相同的布局并且未在所有布局文件中提及视图时，会发生此错误，例如：activity_main.xml(v21) 或 activity_main(land) 等等。所有布局都应包含具有相同 ID 的所有视图。

修复：我有另一个导致问题的 activity_home(v21) 布局。确保您没有多个会导致问题的布局。它在 v21 版本的布局中没有检测到 LayoutManager。