RecyclerView 项目在我滚动它之前不会出现
RecyclerView Items doesn't appear until i scroll it
我在 Fragment 后面的 Google's sample of MVP Android architecture and I tried to make the View part passive as possible following this article 中使用 Recyclerview ，这使得数据模型和演示者的整个 Recyclerview Adapter 被动处理它。
这是我的片段代码：
class OrderHistoryFragment : Fragment(), OrderHistoryContract.View {
lateinit var mPresenter: OrderHistoryContract.Presenter
lateinit var rvOrderHistory: RecyclerView
lateinit var orderHistoryAdapter : OrderHistoryAdapter
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val root = inflater!!.inflate(R.layout.order_history_fragment, container, false)
rvOrderHistory = root.findViewById<RecyclerView>(R.id.rvOrderHistory)
rvOrderHistory.layoutManager = LinearLayoutManager(context, LinearLayout.VERTICAL, false)
orderHistoryAdapter = OrderHistoryAdapter(mPresenter, object : HistoryItemListener {
override fun onReorder(orderHistory: OrderHistory) {
}
override fun onOpenOrder(orderHistory: OrderHistory) {
val orderIntent = Intent(activity, OrderDetailActivity::class.java)
orderIntent.putExtra("orderId", orderHistory.id)
startActivity(orderIntent)
}
})
rvOrderHistory.adapter = orderHistoryAdapter
return root
}
override fun onResume() {
super.onResume()
mPresenter.start()
}
override fun setPresenter(presenter: OrderHistoryContract.Presenter) {
mPresenter = checkNotNull<OrderHistoryContract.Presenter>(presenter)
}
override fun showLoadingIndicator(load: Boolean?) {
}
override fun updateOrdersAdapter() {
orderHistoryAdapter.notifyDataSetChanged()
}
override fun showSnackBar(Message: String) {
val parentLayout = activity.findViewById<View>(android.R.id.content)
val snackBar = Snackbar
.make(parentLayout, Message, Snackbar.LENGTH_INDEFINITE)
snackBar.setAction("Dismiss") { snackBar.dismiss() }
snackBar.setActionTextColor(Color.RED)
snackBar.show()
}
interface HistoryItemListener {
fun onReorder(orderHistory: OrderHistory)
fun onOpenOrder(orderHistory: OrderHistory)
}
companion object {
fun newInstance(): OrderHistoryFragment {
return OrderHistoryFragment()
}
}
fun OrderHistoryFragment() {
}
}
这是我的 RecyclerView 适配器代码
class OrderHistoryAdapter(internal var orderHistoryPresenter: OrderHistoryContract.Presenter, private val listener: OrderHistoryFragment.HistoryItemListener) : RecyclerView.Adapter<OrderHistoryAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.order_history_item, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
orderHistoryPresenter.onBindOrdersRow(position, holder)
holder.bReOrder!!.setOnClickListener { v -> listener.onReorder(orderHistoryPresenter.getOrderHistoryItem(position)) }
holder.cvOrderItem!!.setOnClickListener { v -> listener.onOpenOrder(orderHistoryPresenter.getOrderHistoryItem(position)) }
}
override fun getItemId(position: Int): Long {
return position.toLong()
}
override fun getItemCount(): Int {
return orderHistoryPresenter.getOrdersCount()
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), OrderHistoryContract.orderRowView {
internal var ivOrderVendor: ImageView? = null
internal var tvOrderId: TextView? = null
internal var tvOrderItems: TextView? = null
internal var tvOrderDate: TextView? = null
internal var tvOrderPrice: TextView? = null
internal var bReOrder: Button? = null
internal var cvOrderItem: CardView? = null
init {
ivOrderVendor = itemView.findViewById<ImageView>(R.id.ivOrderVendor)
tvOrderId = itemView.findViewById<TextView>(R.id.tvOrderId)
tvOrderItems = itemView.findViewById<TextView>(R.id.tvOrderItems)
tvOrderDate = itemView.findViewById<TextView>(R.id.tvOrderDate)
tvOrderPrice = itemView.findViewById<TextView>(R.id.tvOrderPrice)
bReOrder = itemView.findViewById<Button>(R.id.bReOrder)
cvOrderItem = itemView.findViewById<CardView>(R.id.cvOrderItem)
}
override fun setOrderImage(url: String) {
Glide.with(itemView.context).load(url).into(ivOrderVendor!!)
}
override fun setOrderDate(orderDate: String) {
tvOrderDate!!.text = orderDate
}
override fun setOrderId(orderId: String) {
tvOrderId!!.text = orderId
}
override fun setOrderItems(orderItems: ArrayList<String>) {
val stringBuilder = StringBuilder()
for (item in orderItems) {
stringBuilder.append(item)
}
tvOrderItems!!.text = stringBuilder.toString()
}
override fun setOrderPrice(orderPrice: String) {
tvOrderPrice!!.text = R.string.price.toString() + " " + orderPrice + " " + R.string.egp
}
}
}
这是处理 Adapter 数据并绑定到 ViewHolder
的演示者代码
class OrderHistoryPresenter internal constructor(mDataRepository: DataRepository, mOrdeHistoryView: OrderHistoryContract.View) : OrderHistoryContract.Presenter {
private val mDataRepository: DataRepository
//refrence of the View to trigger the functions after proccessing the task
private val mOrdeHistoryView: OrderHistoryContract.View
private var orderHistoryItems = ArrayList<OrderHistory>()
init {
this.mDataRepository = checkNotNull(mDataRepository, "tasksRepository cannot be null")
this.mOrdeHistoryView = checkNotNull<OrderHistoryContract.View>(mOrdeHistoryView, "tasksView cannot be null!")
mOrdeHistoryView.setPresenter(this)
}
override fun start() {
mOrdeHistoryView.showLoadingIndicator(true)
mDataRepository.getCurrentUser(object : LocalDataSource.userRequestCallback {
override fun onUserRequestSuccess(botitUser: BotitUser) {
val urlParams = HashMap<String, String>()
urlParams.put(Endpoints.USER_ID_KEY, botitUser.userId!!)
val url = Endpoints.getUrl(Endpoints.urls.ORDER_HISTORY, urlParams)
mDataRepository.buildEndPointRequest(url, " ", Endpoints.requestsType.GET, object : EndpointDataSource.RequestCallback {
override fun onRequestSuccess(Body: String) {
try {
mOrdeHistoryView.showLoadingIndicator(false)
orderHistoryItems = JSONParser.parseData(JSONParser.parsers.ORDER_HISTORY, JSONObject(Body)) as ArrayList<OrderHistory>
mOrdeHistoryView.updateOrdersAdapter()
} catch (e: JSONException) {
e.printStackTrace()
}
}
override fun onRequestError(Body: String) {
mOrdeHistoryView.showLoadingIndicator(false)
mOrdeHistoryView.showSnackBar("Cannot load data")
}
})
}
override fun onUserRequestError(Body: String) {
}
})
}
override fun refreshData() {
}
override fun getOrdersCount(): Int {
return orderHistoryItems.size
}
override fun onBindOrdersRow(position: Int, orderViewHolder: OrderHistoryContract.orderRowView) {
if (orderHistoryItems.isNotEmpty()) {
val orderHistory = orderHistoryItems[position]
// orderViewHolder.setOrderDate(orderHistory.orderDate!!)
orderViewHolder.setOrderId(orderHistory.orderId!!)
orderViewHolder.setOrderImage(orderHistory.orderImage!!)
orderViewHolder.setOrderItems(orderHistory.orderItems)
orderViewHolder.setOrderPrice(orderHistory.orderPrice!!)
}
}
override fun getOrderHistoryItem(position: Int): OrderHistory {
return orderHistoryItems[position]
}
override fun actionReOrder(ordreId: String) {
}
}
这里是FragmentXML
<android.support.v7.widget.RecyclerView android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/rvOrderHistory"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
</android.support.v7.widget.RecyclerView>
这是 RecyclerView 项目 XML order_history_item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView 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"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/cvOrderItem"
android:layout_margin="4dp"
android:orientation="vertical">
<android.support.constraint.ConstraintLayout 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"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="8dp">
<ImageView
android:id="@+id/ivOrderVendor"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/mac" />
<TextView
android:id="@+id/tvOrderId"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Order #2123"
android:textAppearance="@style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toRightOf="@+id/ivOrderVendor"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvOrderItems"
android:layout_width="242dp"
android:layout_height="35dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:text="MacDonald’s: Big Mac Beef, Big Tasty Beef. El Ezaby: Signal 2, Pantene Shampoo"
android:textAppearance="@style/TextAppearance.AppCompat.Small"
android:layout_marginRight="8dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/tvOrderId"
app:layout_constraintLeft_toRightOf="@+id/ivOrderVendor"
android:layout_marginLeft="8dp"
app:layout_constraintHorizontal_bias="0.0" />
<TextView
android:id="@+id/tvOrderDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginTop="8dp"
android:text="03:22 PM 23/2/2017"
app:layout_constraintBottom_toTopOf="@+id/tvOrderItems"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintHorizontal_bias="1.0" />
<TextView
android:id="@+id/tvOrderPrice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:text="Price: 225.50 LE"
android:textAppearance="@style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvOrderItems" />
<Button
android:id="@+id/bReOrder"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_margin="4dp"
android:background="@drawable/chip_accent"
android:foreground="?attr/selectableItemBackground"
android:orientation="vertical"
android:padding="8dp"
android:text="Order Again"
android:textAllCaps="false"
android:textColor="@color/colorAccent"
android:textSize="15sp"
app:layout_constraintHorizontal_bias="0.937"
app:layout_constraintLeft_toRightOf="@+id/tvOrderPrice"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvOrderItems"
tools:layout_editor_absoluteY="74dp" />
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>
问题是当我启动显示 Fragment 的 Activity 时，RecyclerView 不显示项目。它仅在我滚动空白 RecyclerView 或将应用程序留在前台并再次返回时出现。
在初始化时 Adapter 的数据是空的，但是 onResume() 我提出了一个更新 Presenter 数据的请求，然后我 notifyDataChange() 在 Adapter 但没有任何更新。
当我调试时我发现 onBindViewHolder() 没有在适配器上的 notifyDataChange() 之后被调用所以我不知道为什么 notifyDataChange() 没有通知 Adapter 数据已更改。
任何人有可能解决此问题的想法或任何解决方案？
我在您的项目 xml 中注意到您的 constraintLayout 高度是 match_parent 对吗？
我建议您将其用作 wrap_content
您需要使用runOnUiThread。
if(activity != null) {
activity!!.runOnUiThread {
root.Recycleview.adapter = Adapter(Array)
Adapter(Array).notifyDataSetChanged()
}
}
看看这个answer
虽然听起来很愚蠢，但在为 recyclerView 设置数据后调用这行代码，帮助我解决了这个问题：
recyclerView.smoothScrollToPosition(0)
PS：我使用的可能与此有关的技术是：RJava、Retrofit2、NavigationUI、Fragments、LiveData 和 Databinding。
编辑：
我在另一个问题上关注@SudoPlz 评论和 answer，它也有效，你必须扩展 RecyclerView 并覆盖 requestLayout：
private boolean mRequestedLayout = false;
@SuppressLint("WrongCall")
@Override
public void requestLayout() {
super.requestLayout();
// We need to intercept this method because if we don't our children will never update
// Check
if (!mRequestedLayout) {
mRequestedLayout = true;
this.post(() -> {
mRequestedLayout = false;
layout(getLeft(), getTop(), getRight(), getBottom());
onLayout(false, getLeft(), getTop(), getRight(), getBottom());
});
}
}
尽管如此，我还是希望在 4、5 年后修复它，但是，这是一个很好的解决方法，您不会忘记它们。
我在 Fragment 后面的 Google's sample of MVP Android architecture and I tried to make the View part passive as possible following this article 中使用 Recyclerview ，这使得数据模型和演示者的整个 Recyclerview Adapter 被动处理它。
这是我的片段代码：
class OrderHistoryFragment : Fragment(), OrderHistoryContract.View {
lateinit var mPresenter: OrderHistoryContract.Presenter
lateinit var rvOrderHistory: RecyclerView
lateinit var orderHistoryAdapter : OrderHistoryAdapter
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
savedInstanceState: Bundle?): View? {
val root = inflater!!.inflate(R.layout.order_history_fragment, container, false)
rvOrderHistory = root.findViewById<RecyclerView>(R.id.rvOrderHistory)
rvOrderHistory.layoutManager = LinearLayoutManager(context, LinearLayout.VERTICAL, false)
orderHistoryAdapter = OrderHistoryAdapter(mPresenter, object : HistoryItemListener {
override fun onReorder(orderHistory: OrderHistory) {
}
override fun onOpenOrder(orderHistory: OrderHistory) {
val orderIntent = Intent(activity, OrderDetailActivity::class.java)
orderIntent.putExtra("orderId", orderHistory.id)
startActivity(orderIntent)
}
})
rvOrderHistory.adapter = orderHistoryAdapter
return root
}
override fun onResume() {
super.onResume()
mPresenter.start()
}
override fun setPresenter(presenter: OrderHistoryContract.Presenter) {
mPresenter = checkNotNull<OrderHistoryContract.Presenter>(presenter)
}
override fun showLoadingIndicator(load: Boolean?) {
}
override fun updateOrdersAdapter() {
orderHistoryAdapter.notifyDataSetChanged()
}
override fun showSnackBar(Message: String) {
val parentLayout = activity.findViewById<View>(android.R.id.content)
val snackBar = Snackbar
.make(parentLayout, Message, Snackbar.LENGTH_INDEFINITE)
snackBar.setAction("Dismiss") { snackBar.dismiss() }
snackBar.setActionTextColor(Color.RED)
snackBar.show()
}
interface HistoryItemListener {
fun onReorder(orderHistory: OrderHistory)
fun onOpenOrder(orderHistory: OrderHistory)
}
companion object {
fun newInstance(): OrderHistoryFragment {
return OrderHistoryFragment()
}
}
fun OrderHistoryFragment() {
}
}
这是我的 RecyclerView 适配器代码
class OrderHistoryAdapter(internal var orderHistoryPresenter: OrderHistoryContract.Presenter, private val listener: OrderHistoryFragment.HistoryItemListener) : RecyclerView.Adapter<OrderHistoryAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = LayoutInflater.from(parent.context)
.inflate(R.layout.order_history_item, parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
orderHistoryPresenter.onBindOrdersRow(position, holder)
holder.bReOrder!!.setOnClickListener { v -> listener.onReorder(orderHistoryPresenter.getOrderHistoryItem(position)) }
holder.cvOrderItem!!.setOnClickListener { v -> listener.onOpenOrder(orderHistoryPresenter.getOrderHistoryItem(position)) }
}
override fun getItemId(position: Int): Long {
return position.toLong()
}
override fun getItemCount(): Int {
return orderHistoryPresenter.getOrdersCount()
}
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView), OrderHistoryContract.orderRowView {
internal var ivOrderVendor: ImageView? = null
internal var tvOrderId: TextView? = null
internal var tvOrderItems: TextView? = null
internal var tvOrderDate: TextView? = null
internal var tvOrderPrice: TextView? = null
internal var bReOrder: Button? = null
internal var cvOrderItem: CardView? = null
init {
ivOrderVendor = itemView.findViewById<ImageView>(R.id.ivOrderVendor)
tvOrderId = itemView.findViewById<TextView>(R.id.tvOrderId)
tvOrderItems = itemView.findViewById<TextView>(R.id.tvOrderItems)
tvOrderDate = itemView.findViewById<TextView>(R.id.tvOrderDate)
tvOrderPrice = itemView.findViewById<TextView>(R.id.tvOrderPrice)
bReOrder = itemView.findViewById<Button>(R.id.bReOrder)
cvOrderItem = itemView.findViewById<CardView>(R.id.cvOrderItem)
}
override fun setOrderImage(url: String) {
Glide.with(itemView.context).load(url).into(ivOrderVendor!!)
}
override fun setOrderDate(orderDate: String) {
tvOrderDate!!.text = orderDate
}
override fun setOrderId(orderId: String) {
tvOrderId!!.text = orderId
}
override fun setOrderItems(orderItems: ArrayList<String>) {
val stringBuilder = StringBuilder()
for (item in orderItems) {
stringBuilder.append(item)
}
tvOrderItems!!.text = stringBuilder.toString()
}
override fun setOrderPrice(orderPrice: String) {
tvOrderPrice!!.text = R.string.price.toString() + " " + orderPrice + " " + R.string.egp
}
}
}
这是处理 Adapter 数据并绑定到 ViewHolder
class OrderHistoryPresenter internal constructor(mDataRepository: DataRepository, mOrdeHistoryView: OrderHistoryContract.View) : OrderHistoryContract.Presenter {
private val mDataRepository: DataRepository
//refrence of the View to trigger the functions after proccessing the task
private val mOrdeHistoryView: OrderHistoryContract.View
private var orderHistoryItems = ArrayList<OrderHistory>()
init {
this.mDataRepository = checkNotNull(mDataRepository, "tasksRepository cannot be null")
this.mOrdeHistoryView = checkNotNull<OrderHistoryContract.View>(mOrdeHistoryView, "tasksView cannot be null!")
mOrdeHistoryView.setPresenter(this)
}
override fun start() {
mOrdeHistoryView.showLoadingIndicator(true)
mDataRepository.getCurrentUser(object : LocalDataSource.userRequestCallback {
override fun onUserRequestSuccess(botitUser: BotitUser) {
val urlParams = HashMap<String, String>()
urlParams.put(Endpoints.USER_ID_KEY, botitUser.userId!!)
val url = Endpoints.getUrl(Endpoints.urls.ORDER_HISTORY, urlParams)
mDataRepository.buildEndPointRequest(url, " ", Endpoints.requestsType.GET, object : EndpointDataSource.RequestCallback {
override fun onRequestSuccess(Body: String) {
try {
mOrdeHistoryView.showLoadingIndicator(false)
orderHistoryItems = JSONParser.parseData(JSONParser.parsers.ORDER_HISTORY, JSONObject(Body)) as ArrayList<OrderHistory>
mOrdeHistoryView.updateOrdersAdapter()
} catch (e: JSONException) {
e.printStackTrace()
}
}
override fun onRequestError(Body: String) {
mOrdeHistoryView.showLoadingIndicator(false)
mOrdeHistoryView.showSnackBar("Cannot load data")
}
})
}
override fun onUserRequestError(Body: String) {
}
})
}
override fun refreshData() {
}
override fun getOrdersCount(): Int {
return orderHistoryItems.size
}
override fun onBindOrdersRow(position: Int, orderViewHolder: OrderHistoryContract.orderRowView) {
if (orderHistoryItems.isNotEmpty()) {
val orderHistory = orderHistoryItems[position]
// orderViewHolder.setOrderDate(orderHistory.orderDate!!)
orderViewHolder.setOrderId(orderHistory.orderId!!)
orderViewHolder.setOrderImage(orderHistory.orderImage!!)
orderViewHolder.setOrderItems(orderHistory.orderItems)
orderViewHolder.setOrderPrice(orderHistory.orderPrice!!)
}
}
override fun getOrderHistoryItem(position: Int): OrderHistory {
return orderHistoryItems[position]
}
override fun actionReOrder(ordreId: String) {
}
}
这里是FragmentXML
<android.support.v7.widget.RecyclerView android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/rvOrderHistory"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
</android.support.v7.widget.RecyclerView>
这是 RecyclerView 项目 XML order_history_item.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView 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"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/cvOrderItem"
android:layout_margin="4dp"
android:orientation="vertical">
<android.support.constraint.ConstraintLayout 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"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:padding="8dp">
<ImageView
android:id="@+id/ivOrderVendor"
android:layout_width="60dp"
android:layout_height="60dp"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/mac" />
<TextView
android:id="@+id/tvOrderId"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="Order #2123"
android:textAppearance="@style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toRightOf="@+id/ivOrderVendor"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvOrderItems"
android:layout_width="242dp"
android:layout_height="35dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:text="MacDonald’s: Big Mac Beef, Big Tasty Beef. El Ezaby: Signal 2, Pantene Shampoo"
android:textAppearance="@style/TextAppearance.AppCompat.Small"
android:layout_marginRight="8dp"
app:layout_constraintRight_toRightOf="parent"
android:layout_marginTop="8dp"
app:layout_constraintTop_toBottomOf="@+id/tvOrderId"
app:layout_constraintLeft_toRightOf="@+id/ivOrderVendor"
android:layout_marginLeft="8dp"
app:layout_constraintHorizontal_bias="0.0" />
<TextView
android:id="@+id/tvOrderDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="16dp"
android:layout_marginRight="16dp"
android:layout_marginTop="8dp"
android:text="03:22 PM 23/2/2017"
app:layout_constraintBottom_toTopOf="@+id/tvOrderItems"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.0"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintHorizontal_bias="1.0" />
<TextView
android:id="@+id/tvOrderPrice"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="8dp"
android:layout_marginLeft="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="16dp"
android:text="Price: 225.50 LE"
android:textAppearance="@style/TextAppearance.AppCompat.Body2"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvOrderItems" />
<Button
android:id="@+id/bReOrder"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_margin="4dp"
android:background="@drawable/chip_accent"
android:foreground="?attr/selectableItemBackground"
android:orientation="vertical"
android:padding="8dp"
android:text="Order Again"
android:textAllCaps="false"
android:textColor="@color/colorAccent"
android:textSize="15sp"
app:layout_constraintHorizontal_bias="0.937"
app:layout_constraintLeft_toRightOf="@+id/tvOrderPrice"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvOrderItems"
tools:layout_editor_absoluteY="74dp" />
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>
问题是当我启动显示 Fragment 的 Activity 时，RecyclerView 不显示项目。它仅在我滚动空白 RecyclerView 或将应用程序留在前台并再次返回时出现。
在初始化时 Adapter 的数据是空的，但是 onResume() 我提出了一个更新 Presenter 数据的请求，然后我 notifyDataChange() 在 Adapter 但没有任何更新。
当我调试时我发现 onBindViewHolder() 没有在适配器上的 notifyDataChange() 之后被调用所以我不知道为什么 notifyDataChange() 没有通知 Adapter 数据已更改。
任何人有可能解决此问题的想法或任何解决方案？
我在您的项目 xml 中注意到您的 constraintLayout 高度是 match_parent 对吗？ 我建议您将其用作 wrap_content
您需要使用runOnUiThread。
if(activity != null) {
activity!!.runOnUiThread {
root.Recycleview.adapter = Adapter(Array)
Adapter(Array).notifyDataSetChanged()
}
}
看看这个answer
虽然听起来很愚蠢，但在为 recyclerView 设置数据后调用这行代码，帮助我解决了这个问题：
recyclerView.smoothScrollToPosition(0)
PS：我使用的可能与此有关的技术是：RJava、Retrofit2、NavigationUI、Fragments、LiveData 和 Databinding。
编辑： 我在另一个问题上关注@SudoPlz 评论和 answer，它也有效，你必须扩展 RecyclerView 并覆盖 requestLayout：
private boolean mRequestedLayout = false;
@SuppressLint("WrongCall")
@Override
public void requestLayout() {
super.requestLayout();
// We need to intercept this method because if we don't our children will never update
// Check
if (!mRequestedLayout) {
mRequestedLayout = true;
this.post(() -> {
mRequestedLayout = false;
layout(getLeft(), getTop(), getRight(), getBottom());
onLayout(false, getLeft(), getTop(), getRight(), getBottom());
});
}
}
尽管如此，我还是希望在 4、5 年后修复它，但是，这是一个很好的解决方法，您不会忘记它们。