[英]Android recyclerView and data binding
我在 Kotlin 中創建了一個 Android 應用程序,我想從網絡服務器獲取一些信息並使用數據綁定放入回收站視圖。 我使用存儲庫模式,所以每次我發出獲取請求時,我都會將信息保存在房間數據庫中,並使用實時數據從中獲取數據。 出於某種原因,我的 ryclerview 沒有顯示任何內容,並且我沒有收到任何錯誤。 請求有效,我得到了數據,但 recyclerview 不起作用。 我的視圖模型:
class HomeViewModel(application: Application) : ViewModel() {
private val availableTicketsRepo = AvailableTicketsRepository(getInstance(application))
val tickets = availableTicketsRepo.availableTickets
init {
refreshDataFromRepository()
}
private fun refreshDataFromRepository() {
viewModelScope.launch {
try {
availableTicketsRepo.refreshAvailableTickets()
} catch (ex: Exception) {
ex.message?.let { Resource.error(data = null, message = it) }
Log.i("Home", "*** Eccezione: ${ex} ***")
}
}
}
我的片段 class (帶適配器和視圖):
package com.example.ticketapp.ui.home
class HomeFragment : Fragment() {
private val viewModel: HomeViewModel by lazy {
val activity = requireNotNull(this.activity) {
"You can only access the viewModel after onActivityCreated()"
}
ViewModelProvider(this, HomeViewModel.Factory(activity.application))
.get(HomeViewModel::class.java)
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
val binding = DataBindingUtil.inflate<FragmentHomeBinding>(
inflater,
R.layout.fragment_home,
container,
false
)
binding.lifecycleOwner = this
binding.viewModel = viewModel
binding.availableTicketsList.adapter = AvailableTicketsAdapter()
return binding.root
}
}
class AvailableTicketsAdapter() :
ListAdapter<AvailableTicket, AvailableTicketsAdapter.AvailableTicketViewHolder>(DiffCallback) {
class AvailableTicketViewHolder(private var binding: AvailableTicketItemsBinding) :
RecyclerView.ViewHolder(binding.root) {
fun bind(tickets: AvailableTicket) {
binding.ticket = tickets
binding.executePendingBindings()
}
}
companion object DiffCallback : DiffUtil.ItemCallback<AvailableTicket>() {
override fun areItemsTheSame(oldItem: AvailableTicket, newItem: AvailableTicket): Boolean {
return oldItem === newItem
}
override fun areContentsTheSame(
oldItem: AvailableTicket,
newItem: AvailableTicket
): Boolean {
return oldItem.Id == newItem.Id
}
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): AvailableTicketViewHolder {
return AvailableTicketViewHolder(
AvailableTicketItemsBinding.inflate(
LayoutInflater.from(
parent.context
)
)
)
}
override fun onBindViewHolder(holder: AvailableTicketViewHolder, position: Int) {
val tickets = getItem(position)
holder.bind(tickets)
}
}
我的存儲庫:
class AvailableTicketsRepository(private val database: TicketDatabase) {
val availableTickets: LiveData<List<AvailableTicket>> =
Transformations.map(database.ticketDatabaseDao.getAvailableTickets()) {
it.asDomainModel()
}
suspend fun refreshAvailableTickets() {
withContext(Dispatchers.IO) {
val tickets = RetrofitBuilder.apiService.getAvailableTickets()
database.ticketDatabaseDao.insertAllAvailableTickets(tickets.map { it.asDataBaseModel() })
}
}
}
recyclerview 中項目的 xml:
<?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>
<import type="android.view.View"/>
<variable
name="ticket"
type="com.example.ticketapp.model.AvailableTicket" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/titleText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ellipsize="end"
android:maxLength="50"
android:text="@{ticket.title}"
android:singleLine="true"
android:textAlignment="center"
android:textSize="16sp"
android:textStyle="bold"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="Titolo di max 50 caratteri per non uscire dalla riga" />
<TextView
android:id="@+id/customerText"
android:layout_width="160dp"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:textSize="14sp"
android:text="@{ticket.customer}"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/titleText"
tools:text="ESEMPIO DI UN REFERENTE" />
<TextView
android:id="@+id/dateText"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:textAlignment="textEnd"
android:textSize="14sp"
android:text="@{ticket.date_Time}"
app:layout_constraintBaseline_toBaselineOf="@+id/customerText"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toBottomOf="@+id/titleText"
tools:text="20/01/2021 10:00:00" />
<ImageView
android:id="@+id/warningImg"
style="@style/iconImg"
android:layout_marginTop="20dp"
android:visibility="@{ticket.triangle ? View.VISIBLE : View.GONE}"
android:foregroundGravity="center"
app:layout_constraintEnd_toStartOf="@+id/dateText"
app:layout_constraintStart_toEndOf="@+id/customerText"
app:layout_constraintTop_toBottomOf="@+id/titleText"
app:srcCompat="@drawable/ic_warning" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
ryclerview的XML:
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/availableTicketsList"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingStart="10dp"
android:paddingEnd="10dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/toolbar"
tools:listitem="@layout/available_ticket_items" />
我的 Model class:
@Parcelize
data class AvailableTicket (
val Id: Int,
val Title: String,
val Description: String,
val Date_Time: String,
val Customer: String,
val Field: String,
val Category: String,
val Color: String,
val Author: String,
val Triangle: Boolean,
val MyPriority: String
): Parcelable
您應該在修改數據時通知適配器,在ViewModel
中添加LiveData
並將其發布在availableTicketsRepo.refreshAvailableTickets()
之后,然后在收到數據后調用適配器內部的submitList
視圖模型
class HomeViewModel(application: Application) : ViewModel() {
private val availableTicketsRepo = AvailableTicketsRepository(getInstance(application))
val tickets = availableTicketsRepo.availableTickets
init {
refreshDataFromRepository()
}
private fun refreshDataFromRepository() {
viewModelScope.launch {
try {
availableTicketsRepo.refreshAvailableTickets()
} catch (ex: Exception) {
ex.message?.let { Resource.error(data = null, message = it) }
Log.i("Home", "*** Eccezione: ${ex} ***")
}
}
}
}
然后在Fragment
中,將列表提交給適配器一旦獲取
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
val binding = DataBindingUtil.inflate<FragmentHomeBinding>(
inflater,
R.layout.fragment_home,
container,
false
)
binding.lifecycleOwner = this
binding.viewModel = viewModel
binding.availableTicketsList.adapter = AvailableTicketsAdapter()
viewModel.tickets.observe(this, Observer{
(binding.availableTicketsList.adapter as? AvailableTicketsAdapter)?.submitList(it)
})
return binding.root
}
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