我正在尝试使用 Kotlin 在 RecyclerView 中查看列表。我正在片段类中编写 RecyclerView id 并在适配器中设置列表（响应），但它没有显示在 RecyclerView 中。下面的代码是写的我不知道我该如何解决这个问题。
项目有一个 Fragment、Adapter、xml 文件和模型类。
fragment_availabletender
这个页面有 RecyclerView。
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<!-- Data to make available to the XML via data binding. In this case,
the whole ViewModel, so that we can access the LiveData,
click handlers, and state variables. -->
<data>
<variable
name="viewModel"
type= "com.bitcomm.main.ui.home.NotificationViewModel" />
</data>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.appcompat.widget.AppCompatSpinner
android:id="@+id/spinner2"
android:layout_width="93dp"
android:layout_height="39dp"
android:layout_alignParentRight="true"
android:entries="@array/array_name"
style="@style/spinnerItemStyle"
android:layout_alignParentEnd="true" />
<androidx.appcompat.widget.AppCompatSpinner
android:id="@+id/spinner1"
android:layout_width="93dp"
android:layout_height="39dp"
android:layout_toLeftOf="@+id/spinner2"
android:entries="@array/array_name1"
style="@style/spinnerItemStyle"
android:layout_toStartOf="@+id/spinner2" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/tender_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#0f3b52"
android:color="@color/cardview_light_background"
android:padding="6dp"
android:layout_below="@+id/spinner2"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
/>
</RelativeLayout>
模型类这个类有模型
data class TenderProperty(
val id: String,
// used to map img_src from the JSON to imgSrcUrl in our class
@Json(name = "img_src") val imgSrcUrl: String,
val type: String,
val price: Double
)
TenderViewModel 这里响应越来越
private val _response = MutableLiveData<List<TenderProperty>>()
// The external immutable LiveData for the response String
val response: LiveData<List<TenderProperty>>
get() = _response
private val _navigateToSelectedProperty = MutableLiveData<TenderProperty>()
val navigateToSelectedProperty: LiveData<TenderProperty>
get() = _navigateToSelectedProperty
// Create a Coroutine scope using a job to be able to cancel when needed
private var viewModelJob = Job()
// the Coroutine runs using the Main (UI) dispatcher
private val coroutineScope = CoroutineScope(viewModelJob + Dispatchers.Main )
/**
* Call getMarsRealEstateProperties() on init so we can display status immediately.
*/
init {
getTenderRealEstateProperties()
}
private fun getTenderRealEstateProperties() {
coroutineScope.launch {
// Get the Deferred object for our Retrofit request
var getPropertiesDeferred = TenderApi.retrofitService.getProperties()
try {
// this will run on a thread managed by Retrofit
val listResult = getPropertiesDeferred.await()
_sortByPrice.value=listResult.toList().sortedBy {it.price}
_sortById.value=listResult.toList().sortedBy {it.id}
_response.value = listResult
println("hii"+_response.value)
Log.d("class","_response.value")
} catch (e: Exception) {
_response.value = ArrayList()
Log.d("class","_response.value")
}
}
}
fun displayPropertyDetails(marsProperty: TenderProperty) {
_navigateToSelectedProperty.value = marsProperty
}
fun displayPropertyDetailsComplete() {
_navigateToSelectedProperty.value = null
}
ListTenderAdapter 这是适配器类
class ListTenderAdapter( private val onClickListener: OnClickListener ) :
ListAdapter<TenderProperty,
ListTenderAdapter.TenderPropertyViewHolder>(DiffCallback) {
class TenderPropertyViewHolder(private var binding:TenderListViewBinding):
RecyclerView.ViewHolder(binding.root) {
fun bind(tenderProperty: TenderProperty) {
binding.property = tenderProperty
// This is important, because it forces the data binding to execute immediately,
// which allows the RecyclerView to make the correct view size measurements
binding.executePendingBindings()
}
}
/**
* Allows the RecyclerView to determine which items have changed when the [List] of [MarsProperty]
* has been updated.
*/
companion object DiffCallback : DiffUtil.ItemCallback<TenderProperty>() {
override fun areItemsTheSame(oldItem: TenderProperty, newItem: TenderProperty): Boolean {
return oldItem === newItem
}
override fun areContentsTheSame(oldItem: TenderProperty, newItem: TenderProperty): Boolean {
return oldItem.id == newItem.id
}
}
/**
* Create new [RecyclerView] item views (invoked by the layout manager)
*/
override fun onCreateViewHolder(parent: ViewGroup,
viewType: Int): TenderPropertyViewHolder {
return TenderPropertyViewHolder(TenderListViewBinding.inflate(LayoutInflater.from(parent.context)))
}
/**
* Replaces the contents of a view (invoked by the layout manager)
*/
override fun onBindViewHolder(holder: TenderPropertyViewHolder, position: Int) {
val tenderProperty = getItem(position)
holder.itemView.setOnClickListener {
onClickListener.onClick(tenderProperty)
}
holder.bind(tenderProperty)
}
/**
* Custom listener that handles clicks on [RecyclerView] items. Passes the [MarsProperty]
* associated with the current item to the [onClick] function.
* @param clickListener lambda that will be called with the current [MarsProperty]
*/
class OnClickListener(val clickListener: (tenderProperty: TenderProperty) -> Unit) {
fun onClick(tenderProperty: TenderProperty) = clickListener(tenderProperty)
}
}
这是片段类
class TenderListFragment : Fragment() {
private val viewModel: NotificationViewModel by lazy {
ViewModelProviders.of(this).get(NotificationViewModel::class.java)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val binding = FragmentAvailabletenderBinding.inflate(inflater)
binding.lifecycleOwner = this
binding.viewModel = viewModel
binding.tenderList.addItemDecoration(MarginItemDecoration(5))
val adapter=binding.tenderList.adapter as ListTenderAdapter
adapter.submitList(viewModel.response.value)
binding.tenderList.adapter = ListTenderAdapter(ListTenderAdapter.OnClickListener {
viewModel.displayPropertyDetails(it)
})
adapter.notifyDataSetChanged()
// binding.tenderList.layoutManager = LinearLayoutManager(activity)
setHasOptionsMenu(true)
return binding.root
}