[英]lateinit property binding has not been initialized
我知道有類似的問題,但我只是找不到類似的東西,我一直在研究新的東西來學習,在將 kotlin 合成轉換為viewvbinding
模式時,我遇到了這個錯誤
kotlin.UninitializedPropertyAccessException: lateinit property binding has not been initialized at com.codepalace.chatbot.ui.MessagingAdapter.onBindViewHolder(MessagingAdapter.kt:60) at com.codepalace.chatbot.ui.MessagingAdapter.onBindViewHolder(MessagingAdapter.kt:17)
它說我必須初始化綁定,但我不知道把它放在哪里。
這是代碼。
class MessagingAdapter: RecyclerView.Adapter<MessagingAdapter.MessageViewHolder>() {
var messagesList = mutableListOf<Message>()
private lateinit var binding: MessageItemBinding
inner class MessageViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
init {
itemView.setOnClickListener {
//Remove message on the item clicked
messagesList.removeAt(adapterPosition)
notifyItemRemoved(adapterPosition)
}
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MessageViewHolder {
return MessageViewHolder(
LayoutInflater.from(parent.context).inflate(R.layout.message_item, parent, false)
)
}
override fun getItemCount(): Int {
return messagesList.size
}
@SuppressLint("SetTextI18n")
override fun onBindViewHolder(holder: MessageViewHolder, position: Int) {
val currentMessage = messagesList[position]
when (currentMessage.id) {
SEND_ID -> {
holder.itemView.findViewById<View>(R.id.tv_message).apply {
binding.tvMessage.text = currentMessage.message
visibility = View.VISIBLE
}
holder.itemView.findViewById<View>(R.id.tv_bot_message).visibility = View.GONE
}
RECEIVE_ID -> {
holder.itemView.findViewById<View>(R.id.tv_bot_message).apply {
binding.tvBotMessage.text = currentMessage.message
visibility = View.VISIBLE
}
holder.itemView.findViewById<View>(R.id.tv_message).visibility = View.GONE
}
}
}
fun insertMessage(message: Message) {
this.messagesList.add(message)
notifyItemInserted(messagesList.size)
}
private lateinit var binding: MessageItemBinding
您沒有初始化binding
object,因為您將其定義為lateinit,那么您應該定義它。
這通常在onCreateViewHolder
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TrackedActivityHolder {
val inflater = LayoutInflater.from(parent.context)
binding = DataBindingUtil.inflate<MessageItemBinding>(inflater, R.layout.message_item, parent, false)
return MessageViewHolder(
binding
)
}
更新
您需要在MessageViewHolder
構造函數中接受MessageItemBinding
類型而不是View
,並使用itemView.root
獲取列表項的根視圖。
inner class MessageViewHolder(itemView: MessageItemBinding) : RecyclerView.ViewHolder(itemView.root) {
init {
itemView.root.setOnClickListener {
//Remove message on the item clicked
messagesList.removeAt(adapterPosition)
notifyItemRemoved(adapterPosition)
}
}
}
您收到此錯誤的原因是MessageItemBinding
不應該在 Adapter 中,而是在 ViewHolder class 中。 您可以像這樣制作 RecyclerView:
object MessageDiffCallback : DiffUtil.ItemCallback<Message>()
{
override fun areItemsTheSame(
oldItem: Message,
newItem: Message
): Boolean =
oldItem.id == newItem.id
override fun areContentsTheSame(
oldItem: Message,
newItem: Message
): Boolean =
oldItem == newItem
}
我假設Message
是數據 class。 您必須創建此MessageDiffCallback
並以與我類似的方式覆蓋這兩個方法。
現在創建ViewHolder
class:
class MessageViewHolder private constructor(
private val binding: MessageItemBinding
) : RecyclerView.ViewHolder(binding.root)
{
companion object
{
fun create(parent: ViewGroup): MessageViewHolder
{
val layoutInflater = LayoutInflater.from(parent.context)
val binding = MessageItemBinding.inflate(layoutInflater, parent, false)
return MessageViewHolder(
binding
)
}
}
fun bind(
message: Messaage
)
{
// Here You can do everything.
// You pass the message and based on this You can set up a view and use binding
}
}
現在適配器 class
class MessageAdapter : ListAdapter<Message, MessageViewHolder>(MessageDiffCallback)
{
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MessageViewHolder =
MessageViewHolder.create(parent)
override fun onBindViewHolder(holder: MessageViewHolder, position: Int) =
holder.bind(
message = getItem(position),
)
}
現在你應該有一個工作適配器。 要將數據放入其中,請在您的片段/活動中使用messageAdapter.submitList(messages)
也許不是最好的答案,因為它會更改您的代碼並使用一些不同的邏輯,但它應該會更好。 您可以在此處查看google 示例代碼或在此處獲取codelab 。 注冊后免費
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