ViewModel在对话框关闭后仍显示旧数据，父片段返回视图

Question

我仍在努力处理视图模型，现在我也有一个对话框和回收视图项目，但如果能得到任何帮助，我会尽可能清楚。

我有一个包含项目的对话框，当其中一个项目被选中并关闭时，应该会将数据返回到我的调用片段，以便所选项目显示在该视图下。

然而，一旦选择了项目并且对话框被取消，我就看不到新选择的项目是UI上显示的项目，而是旧项目。(当片段第一次启动时，它会显示在我的列表中设置为选中的项目。选中的值最初是硬编码的，但当单击该项目时会更新。当我在对话框的onDismiss方法中调试视图模型观测器时，我可以看到更新已经发生(。

我在这方面花了几个小时，尝试了一些不同的事情，比如在onResume或onDismiss中调用视图模型，并根据这篇帖子将视图模型更改为启动by by activityViewModels()，但到目前为止，这些都不起作用，我想我现在陷入了困境。下面是我最新版本的代码。

class CovidCheckInFragment : Fragment(R.layout.fragment_covid_check_in) {
var navController: NavController? = null
private val model: MainViewModel by activityViewModels()
@RequiresApi(Build.VERSION_CODES.M)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
navController = Navigation.findNavController(view)

model.userMutableLiveData.observe(viewLifecycleOwner, Observer<Any?> { list ->
if (list != null)
(list as Iterable<*>).map {
if ((it as ModelDialogOption).selected == true) {
tvHeader.text = it.title
}
}
})
}
}

class MyDialogFragment : DialogFragment(), RecyclerDialogOptionsItem.AdapterListener {
private val viewModel: MainViewModel by activityViewModels()
private lateinit var adapter: GroupAdapter<GroupieViewHolder>
var selectedPosition = -1
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setStyle(STYLE_NO_TITLE, R.style.AppTheme_Dialog_Custom)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dialog, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)

rvOptions.layoutManager = LinearLayoutManager(activity)
adapter = GroupAdapter()
rvOptions.adapter = adapter

ivClose.setOnClickListener {
this.dismiss()
}

initViewModel()
}
private fun initViewModel() {
viewModel.userMutableLiveData.observe(this, Observer { list ->
for (i in list!!) {
adapter.add(
RecyclerDialogOptionsItem(
this@MyDialogFragment,
i,
this@MyDialogFragment
)
)
}
})
}
override fun onClickItem(position: Int) {
selectedPosition = position
adapter.notifyDataSetChanged()
Log.i("clicked", "position: $position")
}
}

class MainViewModel : ViewModel() {
private var list: ArrayList<ModelDialogOption>? = null
val userMutableLiveData: MutableLiveData<ArrayList<ModelDialogOption>?> = MutableLiveData()
init {
populateList()
userMutableLiveData.value = list!!
}
private fun populateList() {
list = ArrayList()
list!!.add(ModelDialogOption("Prefer not to say", false))
list!!.add(ModelDialogOption("16-39", false))
list!!.add(ModelDialogOption("40-59", true))
list!!.add(ModelDialogOption("60+", false))
}
}

class RecyclerDialogOptionsItem(
private val fragment: MyDialogFragment,
private val modelDialogOption: ModelDialogOption,
private val adapterListener: AdapterListener
) : Item<GroupieViewHolder>() {
companion object {
var clickListener: AdapterListener? = null
}
override fun bind(viewHolder: GroupieViewHolder, position: Int) {
viewHolder.apply {
with(viewHolder.itemView) {
tvTitle.text = modelDialogOption.title
clickListener = adapterListener
if (fragment.selectedPosition == position) {
ivChecked.visible()
modelDialogOption.selected = true
} else {
ivChecked.invisible()
modelDialogOption.selected = false
}
itemView.setOnClickListener {
clickListener?.onClickItem(adapterPosition)
}
}
}
}
override fun getLayout() = R.layout.rv_options_item_row
interface AdapterListener {
fun onClickItem(position: Int)
}
}

非常感谢。

Answer 1

您的主视图模型应该是这样的

class MainViewModel : ViewModel() {
private var list: ArrayList<ModelDialogOption>? = null
val userMutableLiveData = MutableLiveData<ArrayList<ModelDialogOption>>()
init {
populateList()
userMutableLiveData.value = list!!
}

private fun populateList() {
list = ArrayList()
list!!.add(ModelDialogOption("Prefer not to say", false))
list!!.add(ModelDialogOption("16-39", false))
list!!.add(ModelDialogOption("40-59", true))
list!!.add(ModelDialogOption("60+", false))
}
fun updateItem(position:Int){
val itemToUpdate = list!!.get(position)
itemToUpdate.selected = !itemToUpdate.selected!!
list!![position] = itemToUpdate
}
fun flushItems(){
userMutableLiveData.value = list!!
}

}

然后从MyDialogFragment应该是这样的。

class MyDialogFragment : DialogFragment(), RecyclerDialogOptionsItem.AdapterListener {
private val viewModel: MainViewModel by activityViewModels()
private lateinit var adapter: GroupAdapter<GroupieViewHolder>
var selectedPosition = -1
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setStyle(STYLE_NO_TITLE, R.style.AppTheme_Dialog_Custom)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dialog, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
rvOptions.layoutManager = LinearLayoutManager(activity)
adapter = GroupAdapter()
rvOptions.adapter = adapter

ivClose.setOnClickListener {
this.dismiss()
}

initViewModel()
}
override fun onDismiss(dialog: DialogInterface) {
super.onDismiss(dialog)
viewModel.flushItems()
}
private fun initViewModel() {
viewModel.userMutableLiveData.observe(this, Observer { list ->
for (i in list!!) {
adapter.add(
RecyclerDialogOptionsItem(
this@MyDialogFragment,
i,
this@MyDialogFragment
)
)
}
})
}

override fun onClickItem(position: Int) {
selectedPosition = position
adapter.notifyDataSetChanged()
viewModel.updateItem(position)
Log.i("clicked", "position: $position")
}

}