当我从 Spinner 获得价值时，应用程序因 kotlin.UninitializedPropertyAccessException 而崩溃

Question

当我硬编码需要更新的值时，我的应用程序可以正常运行并更新 firestore 中的字段。但是，当我使用以下代码从 spinner 获取值以更新 firestore 中的字段时，应用程序崩溃了。

我正在使用kotlin 和viewBinding。

以下是Logcat中的错误

--------- beginning of crash 2021-06-07 14:00:12.155 23175-23175/com.trad E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.trad, PID: 23175
kotlin.UninitializedPropertyAccessException: lateinit property binding has not been initialized
    at com.trad.ui.adapters.OrderStatusListAdapter.access$getBinding$p(OrderStatusListAdapter.kt:32)
    at com.trad.ui.adapters.OrderStatusListAdapter$onBindViewHolder$1.onClick(OrderStatusListAdapter.kt:84)
    at android.view.View.performClick(View.java:8160)
    at android.widget.TextView.performClick(TextView.java:16222)
    at android.view.View.performClickInternal(View.java:8137)
    at android.view.View.access$3700(View.java:888)
    at android.view.View$PerformClick.run(View.java:30236)
    at android.os.Handler.handleCallback(Handler.java:938)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:246)
    at android.app.ActivityThread.main(ActivityThread.java:8512)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)

2021-06-07 14:00:12.234 23175-23175/com.trad I/Process: 发送 信号。 PID：23175 SIG：9

下面是OrderStatusListAdapter.kt 类 指向第 32 行和第 84 行的错误在代码中作为注释提及。

open class OrderStatusListAdapter(         //LINE # 32 MENTIONED IN THE ERROR
        private val context: Context,
        private var list: ArrayList<OrderStatus>,
    
        ) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
        lateinit var newOrderStatus: Spinner
        private lateinit var binding: OrderStatusLayoutBinding
    
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
    
            return MyViewHolder(
                LayoutInflater.from(context).inflate(
                    R.layout.order_status_layout,
                    parent,
                    false
                )
            )
        }
    
        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
            val model = list[position]
    
            if (holder is MyViewHolder) {
    
                GlideLoader(context).loadProductPicture(
                    model.image,
                    holder.itemView.iv_order_status_item_image
                )
    
                val dateFormat = "dd MMM yyyy HH:mm"
                
                val formatter = SimpleDateFormat(dateFormat, Locale.getDefault())
    
                val calendar: Calendar = Calendar.getInstance()
                calendar.timeInMillis = model.order_datetime
    
                val orderDateTime = formatter.format(calendar.time)
                holder.itemView.tv_order_status_order_date.text = orderDateTime
    
    
                holder.itemView.tv_order_status_item_name.text = model.items[0].title
                holder.itemView.tv_order_status_item_price.text = "$${model.total_amount}"
 model.order_datetime.toString()
                holder.itemView.tv_order_status.text = model.order_status
                holder.itemView.tv_order_status_order_id.text = model.id
    
                holder.itemView.btn_order_status_change_status.setOnClickListener {
    
    binding.spnOrderChangeStatus.onItemSelectedListener = // LINE 84 MENTIONED IN THE ERROR
                        object : AdapterView.OnItemSelectedListener {
                            override fun onItemSelected(
                                parent: AdapterView<*>?,
                                view: View?,
                                position: Int,
                                id: Long
                            ) {
                                Toast.makeText(
                                    context,
                                    "Selected value is ${
                                        parent?.getItemAtPosition(position).toString()
                                    }",
                                    Toast.LENGTH_SHORT
                                ).show()
    
                                val newstat = parent?.getItemAtPosition(position).toString()
                                FirestoreClass().updateOrderStatus(model.id, newstat)
    
                            }
    
                            override fun onNothingSelected(parent: AdapterView<*>?) {
    
                            }
                        }
                }
    
                holder.itemView.ib_order_status_delete_product.visibility = View.GONE
    
                holder.itemView.setOnClickListener {
                    val intent = Intent(context, SoldProductDetailsActivity::class.java)
                    intent.putExtra(Constants.EXTRA_SOLD_PRODUCT_DETAILS, model)
                    context.startActivity(intent)
                }
    
    
            }
    
        }
    
    
        override fun getItemCount(): Int {
            return list.size
        }
    
    
        class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
    }

Answer 1

发生崩溃，因为绑定未初始化。更改 ViewHolder 构造函数：

class MyViewHolder(private val binding : OrderStatusLayoutBinding) : RecyclerView.ViewHolder(binding.root)
 

还要更改 onCreateViewHolder 方法

 return ViewHolder(OrderStatusLayoutBinding.inflate(LayoutInflater.from(parent.context), parent,false))

Answer 2

kotlin.UninitializedPropertyAccessException: lateinit property binding has not been initialized

表示您在 binding 属性被初始化之前尝试使用它。

binding 应该在你定义布局的地方声明；这通常是在onCreateViewHolder() 回调中，您在其中定义了默认充气器而不使用数据绑定，以解决该问题：

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {

    val inflater = LayoutInflater.from(parent.context)

    // initialize the binding either use:
    binding = DataBindingUtil.inflate(inflater, R.layout.order_status_layout, parent, false) 
    // or use:
    // binding = OrderStatusLayoutBinding.inflate(inflater)

    return MyViewHolder(binding)
}

第二个问题：您在MyViewHolder 中接受View 作为构造函数参数，而它应该接受OrderStatusLayoutBinding 的项目绑定类型

class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)

解决这个问题：

class MyViewHolder(binding: OrderStatusLayoutBinding) : RecyclerView.ViewHolder(binding.root)

更新

我收到了error Unresolved reference: DataBindingUtil alsoDataBindingUtil and inflater in binding = DataBindingUtil.inflate(inflater, R.layout.order_status_layout, parent, false) are red.

您需要在 build.gradle（模块级别）中启用 dataBinding，这需要有 kotlin-kapt 插件：

plugins {
    …
    id 'kotlin-kapt'
}
android {
    …
    buildFeatures {
        dataBinding true
    }
}