我自定义了一个RecyclerView类,它将显示val backupItemList的内容：List< MSetting>在代码B的Kotlin
现在我在RecyclerView类之外修改backupItemList的数据,我认为Code D会在UI中显示最新数据,但是我失败了,UI仍然显示旧数据.
我必须使用Code 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)
}
}
}
}
至civic.LiLister：
如果我使用代码E(我用var替换val),代码C和代码D都得到相同的结果,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,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)
}
}
}
}
解决方法
这个秘密可能隐藏在这里：
class CustomAdapter(val backupItemList：List)
当您初始化CustomAdapter的实例时,该值将复制到属性backupItemList,而不是分配引用.因此,当您更改UIMain的属性allList时,backupItemList将不会按预期更改.
解决方案很简单,正如Ganesh Tikone所写：添加一个方法来更新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.
