在我的应用程序中，当我在一个使用FirebaseRecyclerPagingAdapter从Firebase实时数据库分页数据的RecyclerView中点击一个项目(Issue)时，它显示了在另一个片段中点击的项目的详细信息(使用导航组件)。这在第一次单击时工作得很好，但是当我返回到上一个片段并第二次单击RecyclerView上的同一项时，该项的详细信息不显示。
因为我使用安全参数通过项id (issueId)到下一个片段,它使用查询重火力点实时数据库和检索显示细节,我决定向我的控制台日志条目id在onViewCreated()来确保第二点击项id被传递和细节(用户添加一个问题)的名字被从数据库检索,但不显示。然后，我注意到一个奇怪的行为。
在第一次单击时，项目id被记录到控制台，详细信息也被记录到控制台，片段显示详细信息。然而，在第二次单击时，项目id被记录到控制台(显示项目id正在被传递)，但详细信息没有记录到控制台，也没有显示在片段中(因此片段显示为空)。现在奇怪的是，当我导航到前一个片段时，我看到详细信息的日志显示了两次。
我注意到的另一个奇怪的事情是，在RecyclerView上的每个项目都有这种奇怪的行为，除了最后一个项目。最后一项在第二次单击时显示其详细信息，但我单击的任何其他项都不会显示。
我还注意到，日志显示了我以前点击过两次的每个项目的详细信息，当我导航回来时，即使我点击了不同的项目
我改变了适配器从FirebaseRecyclerPagingAdapter到FirebaseRecyclerAdapter，一切工作正常。当我改回使用FirebaseRecyclerPagingAdapter时，同样的问题仍然存在。
这是一个bug在我的代码或FirebaseRecyclerPagingAdapter本身。可能是什么问题，我能做些什么来解决它?
下面是FirebaseRecyclerPagingAdapter:
package com.colley.android.adapter
import android.annotation.SuppressLint
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.bumptech.glide.load.engine.DiskCacheStrategy
import com.colley.android.R
import com.colley.android.databinding.ItemIssueBinding
import com.colley.android.model.Issue
import com.colley.android.model.Profile
import com.firebase.ui.database.paging.DatabasePagingOptions
import com.firebase.ui.database.paging.FirebaseRecyclerPagingAdapter
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.ValueEventListener
import com.google.firebase.database.ktx.database
import com.google.firebase.database.ktx.getValue
import com.google.firebase.ktx.Firebase
class IssuesPagingAdapter(
options: DatabasePagingOptions<Issue>,
private val context: Context,
private val currentUser: FirebaseUser?,
private val clickListener: IssuePagingItemClickedListener
) : FirebaseRecyclerPagingAdapter<Issue, IssuePagingViewHolder>(options) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): IssuePagingViewHolder {
val viewBinding = ItemIssueBinding
.inflate(LayoutInflater.from(parent.context), parent, false)
return IssuePagingViewHolder(viewBinding)
}
override fun onBindViewHolder(viewHolder: IssuePagingViewHolder, position: Int, model: Issue) {
viewHolder.bind(currentUser, model, context, clickListener)
}
interface IssuePagingItemClickedListener {
fun onItemClick(issueId: String, view: View)
fun onItemLongCLicked(issueId: String, view: View)
fun onUserClicked(userId: String, view: View)
}
}
class IssuePagingViewHolder (private val itemBinding : ItemIssueBinding) : RecyclerView.ViewHolder(itemBinding.root) {
@SuppressLint("SetTextI18n")
fun bind(
currentUser: FirebaseUser?,
issue: Issue, context: Context,
clickListener: IssuesPagingAdapter.IssuePagingItemClickedListener) = with(itemBinding) {
//set issue title, body, timeStamp, contributions and endorsements count
issueTitleTextView.text = issue.title
issueBodyTextView.text = issue.body
issueTimeStampTextView.text = issue.timeStamp
contributionsTextView.text = issue.contributionsCount.toString()
endorsementTextView.text = issue.endorsementsCount.toString()
//check if userId is not null
issue.userId?.let { userId ->
//retrieve user profile
Firebase.database.reference.child("profiles").child(userId)
.addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val profile = snapshot.getValue<Profile>()
if (profile != null) {
//set the name of user who raised this issue
userNameTextView.text = profile.name
//set the school of the user who raised this issue
userSchoolTextView.text = profile.school
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
//retrieve user photo
Firebase.database.reference.child("photos").child(userId)
.addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val photo = snapshot.getValue<String>()
//set photo
if (photo != null) {
Glide.with(root.context).load(photo)
.diskCacheStrategy(DiskCacheStrategy.RESOURCE).into(userImageView)
} else {
Glide.with(root.context).load(R.drawable.ic_person).into(userImageView)
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
}
root.setOnClickListener {
if(issue.issueId != null) {
clickListener.onItemClick(issue.issueId, it)
}
}
root.setOnLongClickListener {
if(issue.issueId != null) {
clickListener.onItemLongCLicked(issue.issueId, it)
}
true
}
userNameTextView.setOnClickListener {
if(issue.userId != null) {
clickListener.onUserClicked(issue.userId, it)
}
}
}
}
下面是显示项目详细信息的片段:
package com.colley.android.view.fragment
import android.os.Bundle
import android.util.Log
import android.view.*
import android.view.View.GONE
import android.view.View.VISIBLE
import android.widget.Toast
import androidx.core.os.bundleOf
import androidx.fragment.app.Fragment
import androidx.navigation.fragment.findNavController
import androidx.navigation.fragment.navArgs
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.bumptech.glide.Glide
import com.colley.android.R
import com.colley.android.adapter.IssuesCommentsRecyclerAdapter
import com.colley.android.databinding.FragmentViewIssueBinding
import com.colley.android.model.Comment
import com.colley.android.model.Issue
import com.colley.android.model.Profile
import com.colley.android.view.dialog.IssueCommentBottomSheetDialogFragment
import com.firebase.ui.database.FirebaseRecyclerOptions
import com.firebase.ui.database.ObservableSnapshotArray
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.auth.ktx.auth
import com.google.firebase.database.*
import com.google.firebase.database.ktx.database
import com.google.firebase.database.ktx.getValue
import com.google.firebase.ktx.Firebase
class ViewIssueFragment :
Fragment(),
IssuesCommentsRecyclerAdapter.ItemClickedListener,
IssuesCommentsRecyclerAdapter.DataChangedListener {
private val args: ViewIssueFragmentArgs by navArgs()
private var _binding: FragmentViewIssueBinding? = null
private val binding get() = _binding
private lateinit var dbRef: DatabaseReference
private lateinit var auth: FirebaseAuth
private lateinit var currentUser: FirebaseUser
private lateinit var recyclerView: RecyclerView
private lateinit var commentSheetDialog: IssueCommentBottomSheetDialogFragment
private var issue: Issue? = null
private var adapter: IssuesCommentsRecyclerAdapter? = null
private var manager: LinearLayoutManager? = null
private val uid: String
get() = currentUser.uid
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentViewIssueBinding.inflate(inflater, container, false)
recyclerView = binding?.issuesCommentsRecyclerView!!
return binding?.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//initialize Realtime Database
dbRef = Firebase.database.reference
//initialize authentication
auth = Firebase.auth
//initialize currentUser
currentUser = auth.currentUser!!
//log item id
Log.d("Log itemId", args.issueId)
//get a query reference to issue comments //order by time stamp
val commentsRef = dbRef.child("issues").child(args.issueId)
.child("comments").orderByChild("commentTimeStamp")
//the FirebaseRecyclerAdapter class and options come from the FirebaseUI library
//build an options to configure adapter. setQuery takes firebase query to listen to and a
//model class to which snapShots should be parsed
val options = FirebaseRecyclerOptions.Builder<Comment>()
.setQuery(commentsRef, Comment::class.java)
.build()
//initialize issue comments adapter
adapter = IssuesCommentsRecyclerAdapter(
options,
currentUser,
this,
this,
requireContext())
manager = LinearLayoutManager(requireContext())
//reversing layout and stacking fron end so that the most recent comments appear at the top
manager?.reverseLayout = true
manager?.stackFromEnd = true
recyclerView.layoutManager = manager
recyclerView.adapter = adapter
dbRef.child("issues").child(args.issueId).addValueEventListener(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
issue = snapshot.getValue<Issue>()
if(issue != null) {
//listener for contrbutions count used to set count text
dbRef.child("issues").child(args.issueId)
.child("contributionsCount").addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val count = snapshot.getValue<Int>()
if(count != null) {
binding?.contributionsTextView?.text = count.toString()
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
//listener for endorsement counts used to set endorsement count text
dbRef.child("issues").child(args.issueId)
.child("endorsementsCount").addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val count = snapshot.getValue<Int>()
if(count != null) {
binding?.endorsementTextView?.text = count.toString()
}
}
override fun onCancelled(error: DatabaseError) {} }
)
//set issue title, body and time stamp, these don't need to change
binding?.issueTitleTextView?.text = issue?.title
binding?.issueBodyTextView?.text = issue?.body
binding?.issueTimeStampTextView?.text = issue?.timeStamp.toString()
//listener for user photo
dbRef.child("photos").child(issue?.userId.toString())
.addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val photo = snapshot.getValue<String>()
if(photo != null) {
context?.let { context -> binding?.userImageView?.let {
imageView ->
Glide.with(context).load(photo).into(
imageView
)
} }
} else {
context?.let { context -> binding?.userImageView?.let {
imageView ->
Glide.with(context).load(R.drawable.ic_profile).into(
imageView
)
} }
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
//listener for profile to set name and school
dbRef.child("profiles").child(issue?.userId.toString())
.addListenerForSingleValueEvent(
object : ValueEventListener {
override fun onDataChange(snapshot: DataSnapshot) {
val profile = snapshot.getValue<Profile>()
if (profile != null) {
//log name details to console
profile.name?.let { Log.d("Log Details", it) }
binding?.userNameTextView?.text = profile.name
binding?.userSchoolTextView?.text = profile.school
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
}
}
override fun onCancelled(error: DatabaseError) {}
}
)
binding?.commentLinearLayout?.setOnClickListener {
commentSheetDialog = IssueCommentBottomSheetDialogFragment(
requireContext(),
requireView())
commentSheetDialog.arguments = bundleOf("issueIdKey" to args.issueId)
commentSheetDialog.show(parentFragmentManager, null)
}
binding?.endorseLinearLayout?.setOnClickListener {
//update contributions count
dbRef.child("issues").child(args.issueId).child("endorsementsCount")
.runTransaction(
object : Transaction.Handler {
override fun doTransaction(currentData: MutableData): Transaction.Result {
//retrieve the current value of endorsement count at this location
var endorsementsCount = currentData.getValue<Int>()
if (endorsementsCount != null) {
//increase the count by 1
endorsementsCount++
//reassign the value to reflect the new update
currentData.value = endorsementsCount
}
//set database issue value to the new update
return Transaction.success(currentData)
}
override fun onComplete(
error: DatabaseError?,
committed: Boolean,
currentData: DataSnapshot?
) {
if (error == null && committed) {
Toast.makeText(requireContext(), "Endorsed", Toast.LENGTH_SHORT)
.show()
}
}
}
)
}
//view profile when clicked
binding?.userImageView?.setOnClickListener {
val action = issue?.userId?.let { it1 ->
ViewIssueFragmentDirections.actionViewIssueFragmentToUserInfoFragment(it1)
}
if (action != null) {
parentFragment?.findNavController()?.navigate(action)
}
}
//view user profile when clicked
binding?.userNameTextView?.setOnClickListener {
val action = issue?.userId?.let { it1 ->
ViewIssueFragmentDirections.actionViewIssueFragmentToUserInfoFragment(it1)
}
if (action != null) {
parentFragment?.findNavController()?.navigate(action)
}
}
}
override fun onItemClick(comment: Comment, view: View) {
//expand comment
}
override fun onItemLongCLicked(comment: Comment, view: View) {
//create option to delete
//create option to respond
}
//view user profile
override fun onUserClicked(userId: String, view: View) {
val action = ViewIssueFragmentDirections.actionViewIssueFragmentToUserInfoFragment(userId)
parentFragment?.findNavController()?.navigate(action)
}
override fun onStart() {
super.onStart()
adapter?.startListening()
}
override fun onStop() {
super.onStop()
adapter?.stopListening()
}
override fun onDestroy() {
super.onDestroy()
_binding = null
}
override fun onDataAvailable(snapshotArray: ObservableSnapshotArray<Comment>) {
//dismiss progress bar once snapshot is available
binding?.issuesCommentProgressBar?.visibility = GONE
//show that there are no comments if snapshot is empty else hide view
//show recycler view if snapshot is not empty else hide
if (snapshotArray.isEmpty()) {
binding?.noCommentsLayout?.visibility = VISIBLE
} else {
binding?.noCommentsLayout?.visibility = GONE
binding?.issuesCommentsRecyclerView?.visibility = VISIBLE
}
}
}
下面是带有recyclerView的片段，显示了我是如何初始化适配器的:
package com.colley.android.view.fragment
import android.os.Bundle
import android.view.*
import android.view.View.GONE
import android.view.View.VISIBLE
import android.widget.Toast
import androidx.fragment.app.Fragment
import androidx.lifecycle.lifecycleScope
import androidx.navigation.fragment.findNavController
import androidx.paging.LoadState
import androidx.paging.PagingConfig
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
import com.colley.android.R
import com.colley.android.adapter.IssuesPagingAdapter
import com.colley.android.databinding.FragmentIssuesBinding
import com.colley.android.model.Issue
import com.firebase.ui.database.paging.DatabasePagingOptions
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.auth.ktx.auth
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseReference
import com.google.firebase.database.ktx.database
import com.google.firebase.ktx.Firebase
import kotlinx.coroutines.flow.collectLatest
import kotlinx.coroutines.launch
class IssuesFragment :
Fragment(),
IssuesPagingAdapter.IssuePagingItemClickedListener {
private var _binding: FragmentIssuesBinding? = null
private val binding get() = _binding!!
private lateinit var dbRef: DatabaseReference
private lateinit var auth: FirebaseAuth
private lateinit var currentUser: FirebaseUser
private var adapter: IssuesPagingAdapter? = null
private var manager: LinearLayoutManager? = null
private lateinit var recyclerView: RecyclerView
private lateinit var swipeRefreshLayout: SwipeRefreshLayout
private val uid: String
get() = currentUser.uid
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//fragment can participate in populating the options menu
setHasOptionsMenu(true)
//initialize Realtime Database
dbRef = Firebase.database.reference
//initialize authentication
auth = Firebase.auth
//initialize currentUser
currentUser = auth.currentUser!!
}
override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
super.onCreateOptionsMenu(menu, inflater)
menu.clear()
inflater.inflate(R.menu.isssues_menu, menu)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
return when (item.itemId) {
R.id.search_issues_menu_item -> {
Toast.makeText(context, "Searching issues", Toast.LENGTH_LONG).show()
true
}
else -> super.onOptionsItemSelected(item)
}
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentIssuesBinding.inflate(inflater, container, false)
recyclerView = binding.issueRecyclerView
swipeRefreshLayout = binding.swipeRefreshLayout
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//get a query reference to issues
val issuesQuery = dbRef.child("issues")
//configuration for how the FirebaseRecyclerPagingAdapter should load pages
val config = PagingConfig(
pageSize = 30,
prefetchDistance = 15,
enablePlaceholders = false
)
//Options to configure an FirebasePagingAdapter
val options = DatabasePagingOptions.Builder<Issue>()
.setLifecycleOwner(viewLifecycleOwner)
.setQuery(issuesQuery, config, Issue::class.java)
.setDiffCallback(object : DiffUtil.ItemCallback<DataSnapshot>() {
override fun areItemsTheSame(
oldItem: DataSnapshot,
newItem: DataSnapshot
): Boolean {
return oldItem.getValue(Issue::class.java)?.issueId == newItem.getValue(Issue::class.java)?.issueId
}
override fun areContentsTheSame(
oldItem: DataSnapshot,
newItem: DataSnapshot
): Boolean {
return oldItem.getValue(Issue::class.java) == newItem.getValue(Issue::class.java)
}
})
.build()
//instantiate adapter
adapter = IssuesPagingAdapter(
options,
requireContext(),
currentUser,
this)
//Perform some action every time data changes or when there is an error.
viewLifecycleOwner.lifecycleScope.launch {
adapter?.loadStateFlow?.collectLatest { loadStates ->
when (loadStates.refresh) {
is LoadState.Error -> {
// The initial load failed. Call the retry() method
// in order to retry the load operation.
Toast.makeText(context, "Error fetching issues! Retrying..", Toast.LENGTH_SHORT).show()
//display no posts available at the moment
binding.noIssuesLayout.visibility = VISIBLE
adapter?.retry()
}
is LoadState.Loading -> {
// The initial Load has begun
// ...
swipeRefreshLayout.isRefreshing = true
}
is LoadState.NotLoading -> {
// The previous load (either initial or additional) completed
swipeRefreshLayout.isRefreshing = false
//remove display no posts available at the moment
binding.noIssuesLayout.visibility = GONE
}
}
when (loadStates.append) {
is LoadState.Error -> {
// The additional load failed. Call the retry() method
// in order to retry the load operation.
adapter?.retry()
}
is LoadState.Loading -> {
// The adapter has started to load an additional page
// ...
swipeRefreshLayout.isRefreshing = true
}
is LoadState.NotLoading -> {
if (loadStates.append.endOfPaginationReached) {
// The adapter has finished loading all of the data set
swipeRefreshLayout.isRefreshing = false
}
}
}
}
}
//set recycler view layout manager
manager = LinearLayoutManager(requireContext())
recyclerView.layoutManager = manager
//initialize adapter
recyclerView.adapter = adapter
swipeRefreshLayout.setOnRefreshListener {
adapter?.refresh()
}
}
override fun onDestroy() {
super.onDestroy()
_binding = null
}
//navigate to new fragment with issue id
override fun onItemClick(issueId: String, view: View) {
val action = HomeFragmentDirections.actionHomeFragmentToViewIssueFragment(issueId)
parentFragment?.findNavController()?.navigate(action)
}
override fun onItemLongCLicked(issueId: String, view: View) {
}
override fun onUserClicked(userId: String, view: View) {
val action = HomeFragmentDirections.actionHomeFragmentToUserInfoFragment(userId)
parentFragment?.findNavController()?.navigate(action)
}
}
点击前
第一次点击
第二次点击
使用addListenerForSingleValueEvent而不是addValueEventListener从显示所单击的项目详细信息的片段中的数据库中查询项目详细信息(issue)。否则，删除onStop()中的addValueEventListener，以便在导航回到前一个片段时侦听器不再连接到数据库。