错误：- Lateinit 属性 itemsList (ArrayList) 尚未初始化，HomeFragment，Kotlin

Question

我正在尝试使用 Kotlin 创建一个故事书应用程序，但我是初学者，正在学习编程。我尝试在 home 片段中使用本地 Json 文件（loadJsonFromAssets）和 glide 创建此应用程序，但出现此错误“lateinit property itemsList 尚未初始化”，我不知道如何修复它，请帮助我修复它。

错误：- Lateinit 属性 itemsList 尚未初始化

首页片段代码

class HomeFragment : Fragment() {

 
    private lateinit var bookAdapter: BookAdapter
    private lateinit var recyclerView: RecyclerView
    private lateinit var itemsList: ArrayList<BooksData>

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

    ): View {
        val view = inflater.inflate(R.layout.fragment_home, container, false)

        // Initialize the RecyclerView
        recyclerView = view.findViewById(R.id.bookRecyclerView)
        recyclerView.layoutManager = GridLayoutManager(requireContext(), 2)
        bookAdapter = BookAdapter(this@HomeFragment, itemsList)
        recyclerView.adapter = bookAdapter
        recyclerView.setHasFixedSize(true)
        itemsList = ArrayList<BooksData>()
        loadData()
        return view
    }

    private fun loadData() {
        val jsonString = loadJson("contents.json")
        val items = parseJson(jsonString)
        bookAdapter.setData(items)

    }

    private fun loadJson(contents: String): String {
        val inputStream = requireContext().assets.open(contents)
        val size = inputStream.available()
        val buffer = ByteArray(size)
        inputStream.read(buffer)
        inputStream.close()
        return String(buffer)
    }

    private fun parseJson(jsonString: String): ArrayList<BooksData> {
        val jsonArray = JSONArray(jsonString)
        val items = ArrayList<BooksData>()
        for (i in 0 until jsonArray.length()) {
            val jsonObject = jsonArray.getJSONObject(i)
            val imageUrl = jsonObject.getString("imageUrl")
            val bookName = jsonObject.getString("bookName")
            items.add(BooksData(imageUrl, bookName))

        }; return items
    }
}

数据类

data class BooksData(val bookName:String, val imageUrl:String){
}

适配器类

class BookAdapter(var context: HomeFragment, private var dataList: ArrayList<BooksData>) :
    RecyclerView.Adapter<BookAdapter.BookViewHolder>() {

    inner class BookViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var bookNameTextView: TextView = itemView.findViewById(R.id.bookName)
        var bookImageView: ImageView = itemView.findViewById(R.id.imageUrl)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): BookViewHolder {
        val view =
            LayoutInflater.from(parent.context).inflate(R.layout.book_category_item, parent, false)
        return BookViewHolder(view)
    }

    override fun getItemCount(): Int = dataList.size
    fun setData(data: ArrayList<BooksData>) {
        dataList.clear()
        dataList.addAll(data)
        notifyDataSetChanged()

    }

    override fun onBindViewHolder(holder: BookViewHolder, position: Int) {
        val item = dataList[position]
        holder.bookNameTextView.text = item.bookName
        Glide.with(context).load(item.imageUrl).placeholder(R.drawable.ic_launcher_background)
            .error(R.drawable.vec_quiz).into(holder.bookImageView)
    }
}

Json 文件

{
"items": \[
{
"bookName": "Basic Grammar",
"imageUrl": "https://drive.google.com/uc?id=1_eVoTO4IeTW1gAbNBb_0-GWASecBNGgS"

    } ,
    {
      "bookName": "Basic Grammar",
      "imageUrl": "https://drive.google.com/uc?id=1_eVoTO4IeTW1gAbNBb_0-GWASecBNGgS"
    
    }

\]
}

请帮我解决这个错误，谢谢

Answer 1

在您的片段的

onCreateView

itemsList

在初始化之前正在使用：

bookAdapter = BookAdapter(this@HomeFragment, itemsList)
//....
itemsList = ArrayList<BooksData>()

您必须首先通过以下任一方式初始化

lateinit

属性

itemsList

：

• 将初始化向上移动：

itemsList = ArrayList<BooksData>()
bookAdapter = BookAdapter(this@HomeFragment, itemsList)

• 将初始化与声明结合起来并去掉

  lateinit

  修饰符：

private var itemsList = ArrayList<BooksData>()