cardView 内的卡片未显示

Question

The cards are not showing when im running the simulator (the recyclerView is showing). I think the problem is in "onCreateView" at AdvertsFragement. My MainActivity activity is with binding inflated. The advertsfragement is embedded in the MainActivity thru a navigation bottom bar.

Card Layout

 <?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/card_view"
    android:layout_margin="5dp"
    app:cardBackgroundColor="@color/oceanBlue"
    app:cardCornerRadius="12dp"
    app:cardElevation="3dp"
    app:contentPadding="4dp"
    >

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/forestGreen"
        android:id="@+id/relativeLayout"
        android:padding="16dp"
        >
        <ImageView
            android:id="@+id/item_image"
            android:layout_width="100dp"
            android:layout_height="100dp"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintLeft_toLeftOf="parent"/>
        <TextView
            android:id="@+id/item_title"
            android:textColor="@color/black"
            android:layout_width="236dp"
            android:layout_height="39dp"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintLeft_toRightOf="@+id/item_image"
            android:layout_marginStart="16dp"
            android:textSize="30sp"/>
        <TextView
            android:id="@+id/item_detail"
            android:textColor="@color/black"
            android:layout_width="236dp"
            android:layout_height="16dp"
            android:layout_marginStart="16dp"
            android:layout_marginTop="8dp"
            app:layout_constraintTop_toBottomOf="@+id/item_title"
            app:layout_constraintLeft_toRightOf="@+id/item_image"/>


    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.cardview.widget.CardView>

Fragment

class AdvertsFragment : Fragment() {

private var layoutManager: RecyclerView.LayoutManager? = null
private var adapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>? = null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

}

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // Inflate the layout for this fragment
    R.id.recycler_view.apply {
        // set a LinearLayoutManager to handle Android
        // RecyclerView behavior
        layoutManager = LinearLayoutManager(activity)
        // set the custom adapter to the RecyclerView
        adapter = RecyclerAdapter()
    }
    return inflater.inflate(R.layout.fragment_adverts, container, false)
}

override fun onViewCreated(itemView: View, savedInstanceState: Bundle?) {
    super.onViewCreated(itemView, savedInstanceState)
}

}

RecyclerAdapter and ViewHolder

class RecyclerAdapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>() {


private var titles = arrayOf("Test1", "Test2", "Test3", "Test4", "Test5")
private var details = arrayOf("Detail1", "Detail2", "Detail3", "Detail4", "Detail5")
private var images = intArrayOf(R.drawable.ic_notifications_black_24dp, R.drawable.ic_notifications_black_24dp, R.drawable.ic_notifications_black_24dp, R.drawable.ic_notifications_black_24dp, R.drawable.ic_notifications_black_24dp)

override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): RecyclerAdapter.ViewHolder{
    val v = LayoutInflater.from(viewGroup.context)
        .inflate(R.layout.card_layout, viewGroup, false)
    return ViewHolder(v)
}

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

override fun onBindViewHolder(holder: ViewHolder, position: Int) {
    holder.itemTitle.text = titles[position]
    holder.itemDetail.text = details[position]
    holder.itemImage.setImageResource(images[position])
}


inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView){
    var itemImage: ImageView
    var itemTitle: TextView
    var itemDetail: TextView

    init {
        itemImage = itemView.findViewById(R.id.item_image)
        itemTitle = itemView.findViewById(R.id.item_title)
        itemDetail = itemView.findViewById(R.id.item_detail)

        itemView.setOnClickListener {
            val position: Int = absoluteAdapterPosition
            Toast.makeText(itemView.context, "you clicked on ${titles[position]}", Toast.LENGTH_LONG).show()
        }

    }

}

}

Answer 1

I just needed to use findViewById() in onViewCreated instead of "R.id.recycler_view.apply" in onCreateView:

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {

    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_adverts, container, false)
}

override fun onViewCreated(itemView: View, savedInstanceState: Bundle?) {
    super.onViewCreated(itemView, savedInstanceState)
    itemView.findViewById<RecyclerView>(R.id.recycler_view).apply{
        // set a LinearLayoutManager to handle Android
        // RecyclerView behavior
        layoutManager = LinearLayoutManager(activity)
        // set the custom adapter to the RecyclerView
        adapter = RecyclerAdapter()
    }
}