android - 当Kotlin中的数据更改时，如何在RecyclerView中重新绑定(bind)项目？

我自定义了一个RecyclerView类，它将在代码B中显示Kotlin中val backupItemList: List<MSetting>的内容

现在，我在RecyclerView类外部修改了backupItemList的数据，我认为代码D将在UI中显示最新数据，但是我失败了，UI仍显示旧数据。
我必须使用代码C来显示最新数据。

代码D有什么问题？

代码A

class UIMain : AppCompatActivity() {
   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.layout_main)

        allList= SettingHandler().getListAllSetting()

        mRecyclerView.layoutManager = LinearLayoutManager(this, LinearLayout.VERTICAL, false)
        mCustomAdapter= CustomAdapter(allList)
        mRecyclerView.adapter= mCustomAdapter


   }


   public override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
       //Code C
       if (resultCode == RESULT_OK) {
           allList=SettingHandler().getListAllSetting()
           mCustomAdapter= CustomAdapter(allList)
           mRecyclerView.adapter= mCustomAdapter
           mCustomAdapter.notifyDataSetChanged()
           mCustomAdapter.setSelectedItem(selectedBackupItem)
       }


       //Code D
       if (resultCode == RESULT_OK) {
          allList=SettingHandler().getListAllSetting()
          mCustomAdapter.setSelectedItem(selectedBackupItem)
       }

   }

}

代码B

  class CustomAdapter (val backupItemList: List<MSetting>) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

        val noRecord=-1
        private var mSelectedItem = noRecord

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

        fun getSelectedItem():Int{
            return  mSelectedItem
        }

        fun setSelectedItem(index:Int){
            if (index in 0..(backupItemList.size-1) ){
                mSelectedItem=index
                notifyDataSetChanged();
            }

        }

        override fun onBindViewHolder(holder: CustomAdapter.ViewHolder, position: Int) {
            holder.bindItems(backupItemList[position])
        }

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

        inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

            fun bindItems(aMSetting: MSetting) {
                itemView.tvSubject.text=aMSetting.name
                itemView.tvCreatedDate.text=aMSetting.createdDate.toDateString()
                itemView.tvDescription.text=aMSetting.description
                itemView.radioButton.setOnClickListener {
                mSelectedItem=adapterPosition
                notifyDataSetChanged();
            }

            if(adapterPosition == 0 && mSelectedItem == noRecord) {
                itemView.radioButton.isChecked = true
                mSelectedItem=adapterPosition
            }
            else {
                itemView.radioButton.isChecked =(adapterPosition == mSelectedItem)
            }
            }

        }

    }

到civic.LiLister:

如果我使用代码E(将val替换为var)，代码C和代码D会得到相同的结果，为什么？

代码E

  class CustomAdapter (var backupItemList: List<MSetting>) : RecyclerView.Adapter<CustomAdapter.ViewHolder>() {

        val noRecord=-1
        private var mSelectedItem = noRecord

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

        fun getSelectedItem():Int{
            return  mSelectedItem
        }

        fun setSelectedItem(index:Int){
            if (index in 0..(backupItemList.size-1) ){
                mSelectedItem=index
                notifyDataSetChanged();
            }

        }

        override fun onBindViewHolder(holder: CustomAdapter.ViewHolder, position: Int) {
            holder.bindItems(backupItemList[position])
        }

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

        inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

            fun bindItems(aMSetting: MSetting) {
                itemView.tvSubject.text=aMSetting.name
                itemView.tvCreatedDate.text=aMSetting.createdDate.toDateString()
                itemView.tvDescription.text=aMSetting.description
                itemView.radioButton.setOnClickListener {
                mSelectedItem=adapterPosition
                notifyDataSetChanged();
            }

            if(adapterPosition == 0 && mSelectedItem == noRecord) {
                itemView.radioButton.isChecked = true
                mSelectedItem=adapterPosition
            }
            else {
                itemView.radioButton.isChecked =(adapterPosition == mSelectedItem)
            }
            }

        }

    }

最佳答案

secret 可能藏在这里:

类CustomAdapter(val backupItemList:List)

初始化CustomAdapter的实例时，该值将复制到属性backupItemList，而不是分配给引用。因此，当您更改UIMain的allList属性时，backupItemList将不会按您预期的那样更改。

正如Ganesh Tikone所写，解决方案很简单:添加一种方法来更新backupItemList。

fun updateData(data: List<MovieModel>) {
    backupItemList.clear()
    backupItemList.addAll(data)
    notifyDataSetChanged()
}

并将代码D更改为:

//Code D
   if (resultCode == RESULT_OK) {
      allList=SettingHandler().getListAllSetting()
      mCustomAdapter.updateData(allList)
      mCustomAdapter.setSelectedItem(selectedBackupItem)
   }

试试。