RecyclerView ListAdapter 不显示特定项目

Question

我的 RecyclerView ListAdapter 没有显示特定项目：

从图中可以看出，除了索引 8 处的项目外，列表中的所有项目都显示出来了。 这个项目没有任何问题，我通过日志检查过。 此外，如果我提供一个包含不同内容的新列表，则会显示一些项目，而另一些则不显示。

这是我的代码：

片段：

class UnicornFragment : Fragment() {

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val binding : FragmentUnicornBinding = DataBindingUtil.inflate(inflater, R.layout.fragment_unicorn, container, false)
        binding.lifecycleOwner = this

        val unicornList = UnicornFragmentArgs.fromBundle(arguments!!).unicornsList

        val adapter = UnicornAdapter()
        binding.unicornsView.adapter = adapter
        Log.e("Unicorn Fragment", "${unicornList.toMutableList().size}")
        adapter.submitList(unicornList.toMutableList())

        return binding.root
    }
}

适配器：

class UnicornAdapter : androidx.recyclerview.widget.ListAdapter<Unicorn, UnicornAdapter.UnicornViewHolder> (DiffCallback){

    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): UnicornViewHolder {
        return UnicornViewHolder(ItemUnicornBinding.inflate(LayoutInflater.from(parent.context)))
    }

    class UnicornViewHolder(private var binding : ItemUnicornBinding) : RecyclerView.ViewHolder(binding.root){
        fun bind(unicorn: Unicorn) {
            binding.unicorn = unicorn

            binding.executePendingBindings()

            Log.e("UnicornAdapter", "Question : ${unicorn.questionText}, Answer : ${unicorn.answerText}")
        }

    }

    override fun onBindViewHolder(holder: UnicornViewHolder, position: Int) {
        holder.bind(getItem(position))
    }

    companion object DiffCallback : DiffUtil.ItemCallback<Unicorn>() {
        override fun areItemsTheSame(oldItem: Unicorn, newItem: Unicorn): Boolean {
            return oldItem === newItem
        }

        override fun areContentsTheSame(oldItem: Unicorn, newItem: Unicorn): Boolean {
             return  oldItem.questionText == newItem.questionText
        }

    }
}

fragment_unicorn.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/colorPrimary">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/unicorns_view"
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />


    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

item_unicorn.xml

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <data>
        <variable
            name="unicorn"
            type="com.example.unicorn.network.Unicorn" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary">

        <TextView
            android:id="@+id/question_text_view"
            style="@style/MainHeading"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginLeft="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginRight="8dp"
            android:fontFamily="sans-serif-black"
            android:gravity="start"
            android:text="@{unicorn.questionText}"
            android:textSize="24sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:text="This is a sample Question" />

        <TextView
            android:id="@+id/answer_text_view"
            style="@style/SubHeading"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:layout_marginLeft="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginBottom="8dp"
            android:gravity="start"
            android:textSize="20sp"
            android:text="@{unicorn.answerText}"
            app:layout_constraintStart_toStartOf="@+id/question_text_view"
            app:layout_constraintTop_toBottomOf="@+id/question_text_view"
            tools:text="Sample Answer" />


    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

日志：

2020-07-01 19:17:51.093 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 1. His brother was accused ……theft., Answer : c)   Of 
2020-07-01 19:17:51.141 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 2. Avail yourself …….this opportunity., Answer : a)    Of
2020-07-01 19:17:51.187 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 3. He is bent ……mischief., Answer : b) On    
2020-07-01 19:17:51.228 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 4. I cannot comply ……..your request, Answer : d)   With
2020-07-01 19:17:51.275 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 5. He is devoid ………all sense of decency. , Answer : b) Of     
2020-07-01 19:17:51.324 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 6. He is endowed …….a strong will., Answer : a)    With  
2020-07-01 19:17:51.369 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 7. Portia was the heiress …….her father’s property, Answer : c)    To
2020-07-01 19:17:51.412 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 8. I congratulate you …….your brilliant success. , Answer : b) On  
2020-07-01 19:17:54.585 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 9. He is blind …….his drawbacks. , Answer : a) To
2020-07-01 19:17:54.679 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 10.    He did not agree ……..my proposal. , Answer : b) To    
2020-07-01 19:17:58.187 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 11.    He as well as you ……guilty., Answer : b)    Is    
2020-07-01 19:17:58.260 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 12.    They are working to live. Identify the verb in this sentence., Answer : b)  Are working 
2020-07-01 19:17:58.328 16433-16433/com.example.unicorn E/UnicornAdapter: Question : 14.    An example for infinite verb is:, Answer : b

可以看出，索引 8 处的项目具有值，就像所有其他项目一样。

任何帮助将不胜感激！

Answer 1

尝试覆盖适配器视图中的 getItemViewType 以返回位置

@Override
public int getItemViewType(int position) { return position; }

Answer 2

问题就在这里：

override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): UnicornViewHolder {
        return UnicornViewHolder(ItemUnicornBinding.inflate(LayoutInflater.from(parent.context)))
    }

改为这个，它工作了：

 override fun onCreateViewHolder(
            parent: ViewGroup,
            viewType: Int
        ): UnicornViewHolder {
            return UnicornViewHolder(ItemUnicornBinding.inflate(LayoutInflater.from(parent.context), parent, false))
        }