NullPointerException：尝试调用虚拟方法和 RecyclerView：没有附加适配器；从 Firestore 获取数据时跳过布局、错误
NullPointerException: Attempt to invoke virtual method & RecyclerView: No adapter attached; skipping layout, errors, when fetching data from Firestore
我试图从 Firestore 中获取数据并将其显示在 RecyclerView 中。但是，我收到以下错误。
我没有太多编码经验，但我尝试在我的项目中添加 RecyclerView 和 fragments。
我正在使用 Kotlin 作为语言。
这三天我一直在想办法找出问题所在和解决方案，但现在我想我必须寻求像你这样的专家的帮助。
以下是我在Logcat
中得到的错误
16273-16273/com.example.quiz E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.quiz, PID: 16273
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quiz/com.example.quiz.ui.activities.DashboardActivity}: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3792)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8512)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
at com.example.quiz.ui.fragments.DashboardFragment.onCreateView(DashboardFragment.kt:28)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2963)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:518)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:282)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2106)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:2002)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3138)
at androidx.fragment.app.FragmentManager.dispatchViewCreated(FragmentManager.java:3065)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:2988)
at androidx.fragment.app.FragmentStateManager.ensureInflatedView(FragmentStateManager.java:392)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:281)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:140)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1067)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:995)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1121)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
at android.view.LayoutInflater.inflate(LayoutInflater.java:680)
at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:699)
2021-05-27 07:25:09.097 16273-16273/com.example.quiz E/AndroidRuntime: at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at com.example.quiz.ui.activities.DashboardActivity.onCreate(DashboardActivity.kt:15)
at android.app.Activity.performCreate(Activity.java:8198)
at android.app.Activity.performCreate(Activity.java:8182)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3765)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8512)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
2021-05-27 07:25:09.166 16273-16273/com.example.quiz I/Process: Sending signal. PID: 16273 SIG: 9
Quiz.kt 文件
package com.example.quiz.models
import android.os.Parcelable
import kotlinx.android.parcel.Parcelize
@Parcelize
data class Quiz(
val user_id: String = "",
var quiz_id: String = "",
val quiz_name: String = "",
val num_participants: String = "",
val num_questions: String = "",
val duration: String = ""
) : Parcelable
DashboardActivity.kt
package com.example.quiz.ui.activities
import android.os.Bundle
import androidx.core.content.ContextCompat
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController
import com.google.android.material.bottomnavigation.BottomNavigationView
import com.example.quiz.R
class DashboardActivity : BaseActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_dashboard)
supportActionBar!!.setBackgroundDrawable(
ContextCompat.getDrawable(
this@DashboardActivity,
R.drawable.app_gradient_color_background
)
)
val navView: BottomNavigationView = findViewById(R.id.nav_view)
val navController = findNavController(R.id.nav_host_fragment)
val appBarConfiguration = AppBarConfiguration(
setOf(
R.id.navigation_quizzes,
R.id.navigation_dashboard
)
)
setupActionBarWithNavController(navController, appBarConfiguration)
navView.setupWithNavController(navController)
}
override fun onBackPressed() {
doubleBackToExit()
}
}
DashboardItemListAdapter.kt
package com.example.quiz.ui.adapters
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.example.quiz.R
import com.example.quiz.models.Quiz
import kotlinx.android.synthetic.main.item_list_layout.view.*
open class DashboardItemsListAdapter(
private val context: Context,
private var list: ArrayList<Quiz>
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var onClickListener: OnClickListener? = null
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_dashboard_layout,
parent,
false
)
)
}
@SuppressLint("SetTextI18n")
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val model = list[position]
if (holder is MyViewHolder) {
holder.itemView.tv_quiz_name.text = model.quiz_name
holder.itemView.tv_participants.text = model.num_participants
holder.itemView.tv_questions.text = model.num_questions
holder.itemView.tv_duration.text = model.duration
holder.itemView.setOnClickListener {
if (onClickListener != null) {
onClickListener!!.onClick(position, model)
}
}
}
}
override fun getItemCount(): Int {
return list.size
}
fun setOnClickListener(onClickListener: OnClickListener) {
this.onClickListener = onClickListener
}
interface OnClickListener {
fun onClick(position: Int, product: Quiz)
}
class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
}
QuizListAdapter.kt
package com.example.quiz.ui.adapters
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.example.quiz.R
import com.example.quiz.models.Quiz
//import com.example.Quiz.utils.GlideLoader
import kotlinx.android.synthetic.main.item_list_layout.view.*
open class QuizListAdapter(
private val context: Context,
private val list: ArrayList<Quiz>,
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_list_layout,
parent,
false
)
)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val model = list[position]
if (holder is MyViewHolder) {
holder.itemView.tv_quiz_name.text = model.quiz_name
holder.itemView.tv_participants.text = model.num_participants
holder.itemView.tv_questions.text = model.num_questions
holder.itemView.tv_duration.text = model.duration
}
}
override fun getItemCount(): Int {
return list.size
}
class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
}
DashboardFragment.kt
package com.example.quiz.ui.fragments
import android.os.Bundle
import android.util.Log
import android.view.*
import androidx.recyclerview.widget.GridLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.DashboardItemsListAdapter
import kotlinx.android.synthetic.main.fragment_dashboard.*
class DashboardFragment : BaseFragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dashboard, container, false)
}
override fun onResume() {
super.onResume()
getDashboardItemsList()
}
private fun getDashboardItemsList() {
showProgressDialog("please_wait")
FirestoreClass().getDashboardItemsList(this@DashboardFragment)
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
hideProgressDialog()
for (i in dashboardItemsList) {
Log.i("Item Title", i.quiz_name)
}
if (dashboardItemsList.size > 0) {
rv_dashboard_items.visibility = View.VISIBLE
tv_no_dashboard_items_found.visibility = View.GONE
rv_dashboard_items.layoutManager = GridLayoutManager(activity, 1)
rv_dashboard_items.setHasFixedSize(true)
val adapter = DashboardItemsListAdapter(requireActivity(), dashboardItemsList)
rv_dashboard_items.adapter = adapter
} else {
rv_dashboard_items.visibility = View.GONE
tv_no_dashboard_items_found.visibility = View.VISIBLE
}
}
}
使用上面的代码，我的应用程序在登录输入用户名和密码后崩溃，但是当我删除 rv_dashboard_items.adapter = adapter 至少应用程序不会崩溃。但是，它根本不显示来自 Firestore 的任何数据。
当我 运行 没有 rv_dashboard_items.adapter = adapter
的应用程序时，出现以下错误
以下代码段中的消息为红色。
E/DashboardFragment: [DocumentSnapshot{key=quizzes/C8STnkYwp3cYWMxm1Y0xQWERTZq1, metadata=SnapshotMetadata{hasPendingWrites=false, isFromCache=false}, doc=Document{key=quizzes/C8STnkYwp3cYWMxm1Y0xQWERTZq1, version=SnapshotVersion(seconds=1621955183, nanos=678854000), type=FOUND_DOCUMENT, documentState=SYNCED, value=ObjectValue{internalValue=# com.google.firestore.v1.Value@1abc2d14
integer_value: 0
map_value {
fields {
key: "quiz_id"
value {
integer_value: 0
string_value: "C8STnkYwp3cYWMxm1Y0xQWERTZq1"
}
}
fields {
key: "num_questions"
value {
integer_value: 0
string_value: "10"
}
}
fields {
key: "quiz_name"
value {
integer_value: 0
string_value: "Easy Quiz"
}
}
fields {
key: "duration"
value {
integer_value: 0
string_value: "10"
}
}
fields {
key: "num_participants"
value {
integer_value: 0
string_value: "5"
}
}
fields {
key: "user_id"
value {
integer_value: 0
string_value: "C8STnkYwp3cYWMxm1Y0xQWERTZq1"
}
}
}}}}]
还有这一行
E/RecyclerView: No adapter attached; skipping layout
QuizFragment.kt
package com.example.quiz.ui.fragments
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.QuizListAdapter
import kotlinx.android.synthetic.main.fragment_quiz.*
class QuizFragment : BaseFragment() {
private lateinit var mRootView: View
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
mRootView = inflater.inflate(R.layout.fragment_quiz, container, false)
return mRootView
}
fun successQuizListFromFireStore(quizList: ArrayList<Quiz>) {
hideProgressDialog()
if (quizList.size > 0) {
rvQuizzesFrag.visibility = View.VISIBLE
tv_no_products_found.visibility = View.GONE
rvQuizzesFrag.layoutManager = LinearLayoutManager(activity)
rvQuizzesFrag.setHasFixedSize(true)
val adapterQuizzes = QuizListAdapter(requireActivity(), quizList)
rvQuizzesFrag.adapter = adapterQuizzes
} else {
rvQuizzesFrag.visibility = View.GONE
tv_no_products_found.visibility = View.VISIBLE
}
}
private fun getQuizListFromFireStore() {
showProgressDialog("Please_wait")
FirestoreClass().getQuizList(this)
}
override fun onResume() {
super.onResume()
getQuizListFromFireStore()
}
}
activity_dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/nav_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="@drawable/app_gradient_color_background"
app:itemIconTint="@color/colorWhite"
app:itemTextColor="@color/colorWhite"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="@menu/bottom_nav_menu" />
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@id/nav_view"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/mobile_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>
fragment_dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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:background="@color/white"
tools:context=".ui.fragments.DashboardFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rv_dashboard_items"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tv_no_dashboard_items_found"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="no_dashboard_item_found"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
fragment_quiz.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
tools:context=".ui.fragments.QuizFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rvQuizzesFrag"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tv_no_products_found"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="NO QUIZZES TODAY"
android:textAlignment="center"
android:textSize="30sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
FirestoreClass.kt
Import 部分代码已从问题中删除，因为我超出了问题中的字符限制。
package com.example.quiz.firestore
class FirestoreClass {
private val mFireStore = FirebaseFirestore.getInstance()
fun getDashboardItemsList(fragment: DashboardFragment) {
mFireStore.collection("quizzes")
.get()
.addOnSuccessListener { document ->
Log.e(fragment.javaClass.simpleName, document.documents.toString())
val quizList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val qz = i.toObject(Quiz::class.java)!!
qz.quiz_id = i.id
quizList.add(qz)
}
fragment.successDashboardItemsList(quizList)
}
.addOnFailureListener { e ->
fragment.hideProgressDialog()
Log.e(fragment.javaClass.simpleName, "Error while getting dashboard items list.", e)
}
}
fun getCurrentUserID(): String {
// An Instance of currentUser using FirebaseAuth
val currentUser = FirebaseAuth.getInstance().currentUser
var currentUserID = ""
if (currentUser != null) {
currentUserID = currentUser.uid
}
return currentUserID
}
fun uploadProductDetails(activity: AddProductActivity, productInfo: Quiz) {
mFireStore.collection("quizzes")
.document()
.set(productInfo, SetOptions.merge())
.addOnSuccessListener {
activity.productUploadSuccess()
}
.addOnFailureListener { e ->
activity.hideProgressDialog()
Log.e(
activity.javaClass.simpleName,
"Error while uploading the product details.",
e
)
}
}
fun getUserDetails(activity: Activity) {
mFireStore.collection("users")
.document(getCurrentUserID())
.get()
.addOnSuccessListener { document ->
Log.i(activity.javaClass.simpleName, document.toString())
val user = document.toObject(User::class.java)!!
val sharedPreferences =
activity.getSharedPreferences(
Constants.MYAPP_PREFERENCES,
Context.MODE_PRIVATE
)
val editor: SharedPreferences.Editor = sharedPreferences.edit()
editor.putString(
Constants.LOGGED_IN_USERNAME,
"${user.firstName} ${user.lastName}"
)
editor.apply()
when (activity) {
is LoginActivity -> {
activity.userLoggedInSuccess(user)
}
}
}
.addOnFailureListener { e ->
when (activity) {
is LoginActivity -> {
activity.hideProgressDialog()
}
}
Log.e(
activity.javaClass.simpleName,
"Error while getting user details.",
e
)
}
}
fun getQuizList(fragment: Fragment) {
mFireStore.collection("quizzes")
.whereEqualTo("user_id", getCurrentUserID())
.get()
.addOnSuccessListener { document ->
Log.e("Products List", document.documents.toString())
val productsList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val product = i.toObject(Quiz::class.java)
product!!.quiz_id = i.id
productsList.add(product)
}
when (fragment) {
is QuizFragment -> {
fragment.successQuizListFromFireStore(productsList)
}
}
}
.addOnFailureListener { e ->
when (fragment) {
is QuizFragment -> {
fragment.hideProgressDialog()
}
}
Log.e("Get Product List", "Error while getting product list.", e)
}
}
fun getAllQuizList(activity: Activity) {
mFireStore.collection("quizzes")
.get()
.addOnSuccessListener { document ->
Log.e("Products List", document.documents.toString())
val productsList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val product = i.toObject(Quiz::class.java)
product!!.quiz_id = i.id
productsList.add(product)
}
}
.addOnFailureListener { e ->
Log.e("Get Product List", "Error while getting all product list.", e)
}
}
}
看了你的代码，我觉得原因是：你的recycleView.
的使用可能有一些小问题
在你的代码中，你似乎在xml的同一个地方使用了两个recycleView，一个是没有数据的recycleView，另一个是recycleView 异步获取数据后。然后在获取数据的函数中控制recycleView的显示和隐藏？
但是，如果在将 recyclerview 附加到 Fragment 后不立即对其进行初始化，您可能会看到 No adapter attached; skipping layout。
解决方法：设置一个recycleView，在Fragment/activity的初始化函数中设置一个空数据给它。 DashboardItemsListAdapter(requireActivity(), listOf<Quiz>())
部分代码：
private lateinit var adapter: DashboardItemsListAdapter
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
adapter = DashboardItemsListAdapter(requestActivity(), arrayListOf<Quiz>())
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
adapter.list = dashboardItemsList
adapter.notifyDataSetChanged()
}
我只是在这里提供我的一个想法。您不能在每次调用 successDashboardItemsList() 时都设置新的适配器。在调用 successDashboardItemsList() 之前，您的适配器应该被初始化（可能没有数据）。每次调用 successDashboardItemsList() 时，
重新分配 Adapter 对象的列表字段的值。并调用Adapter对象的notifyDataSetChanged()，这样问题就解决了
import android.os.Bundle
import android.util.Log
import android.view.*
import androidx.recyclerview.widget.GridLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.DashboardItemsListAdapter
import kotlinx.android.synthetic.main.fragment_dashboard.*
class DashboardFragment : BaseFragment() {
private lateinit var adapter: DashboardItemsListAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dashboard, container, false)
}
private lateinit var recyclerView: RecyclerView
private lateinit var textView: TextView
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
recyclerView = view.findViewById<RecyclerView>(R.id.rv_dashboard_items)
textView = view.findViewById(R.id.tv_no_dashboard_items_found)
adapter = DashboardItemsListAdapter(requireActivity(), arrayListOf<Quiz>())
recyclerView.layoutManager = GridLayoutManager(requireContext(), 1)
recyclerView.setHasFixedSize(true)
recyclerView.adapter = adapter
}
override fun onResume() {
super.onResume()
getDashboardItemsList()
}
private fun getDashboardItemsList() {
showProgressDialog("please_wait")
FirestoreClass().getDashboardItemsList(this@DashboardFragment)
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
hideProgressDialog()
for (i in dashboardItemsList) {
Log.i("Item Title", i.quiz_name)
}
if (dashboardItemsList.size > 0) {
recyclerView.visibility = View.VISIBLE
textView.visibility = View.GONE
adapter.list = dashboardItemsList
adapter.notifyDataSetChanged()
} else {
recyclerView.visibility = View.GONE
textView.visibility = View.VISIBLE
}
}
}
DashboardItemListAdapter.kt
变为：
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_list_layout,
parent,
false
)
)
}
在您的 DashboardItemsListAdapter 中，您正在膨胀 item_dashboard_layout 但您正在为 fragment_dashboard.
导入合成绑定
膨胀的布局可能不包含 fragment_dashboard 绑定所需的视图，因此绑定 returns 为空值。
确保您对膨胀和视图绑定使用相同的布局。
我试图从 Firestore 中获取数据并将其显示在 RecyclerView 中。但是，我收到以下错误。
我没有太多编码经验，但我尝试在我的项目中添加 RecyclerView 和 fragments。
我正在使用 Kotlin 作为语言。
这三天我一直在想办法找出问题所在和解决方案，但现在我想我必须寻求像你这样的专家的帮助。
以下是我在Logcat
16273-16273/com.example.quiz E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.quiz, PID: 16273
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quiz/com.example.quiz.ui.activities.DashboardActivity}: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3792)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8512)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #32 in com.example.quiz:layout/activity_dashboard: Error inflating class fragment
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setLayoutManager(androidx.recyclerview.widget.RecyclerView$LayoutManager)' on a null object reference
at com.example.quiz.ui.fragments.DashboardFragment.onCreateView(DashboardFragment.kt:28)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2963)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:518)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:282)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2106)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:2002)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3138)
at androidx.fragment.app.FragmentManager.dispatchViewCreated(FragmentManager.java:3065)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:2988)
at androidx.fragment.app.FragmentStateManager.ensureInflatedView(FragmentStateManager.java:392)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:281)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:140)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:135)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:319)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:298)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1067)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:995)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1121)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082)
at android.view.LayoutInflater.inflate(LayoutInflater.java:680)
at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:699)
2021-05-27 07:25:09.097 16273-16273/com.example.quiz E/AndroidRuntime: at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at com.example.quiz.ui.activities.DashboardActivity.onCreate(DashboardActivity.kt:15)
at android.app.Activity.performCreate(Activity.java:8198)
at android.app.Activity.performCreate(Activity.java:8182)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3765)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3968)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2307)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8512)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
2021-05-27 07:25:09.166 16273-16273/com.example.quiz I/Process: Sending signal. PID: 16273 SIG: 9
Quiz.kt 文件
package com.example.quiz.models
import android.os.Parcelable
import kotlinx.android.parcel.Parcelize
@Parcelize
data class Quiz(
val user_id: String = "",
var quiz_id: String = "",
val quiz_name: String = "",
val num_participants: String = "",
val num_questions: String = "",
val duration: String = ""
) : Parcelable
DashboardActivity.kt
package com.example.quiz.ui.activities
import android.os.Bundle
import androidx.core.content.ContextCompat
import androidx.navigation.findNavController
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.setupActionBarWithNavController
import androidx.navigation.ui.setupWithNavController
import com.google.android.material.bottomnavigation.BottomNavigationView
import com.example.quiz.R
class DashboardActivity : BaseActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_dashboard)
supportActionBar!!.setBackgroundDrawable(
ContextCompat.getDrawable(
this@DashboardActivity,
R.drawable.app_gradient_color_background
)
)
val navView: BottomNavigationView = findViewById(R.id.nav_view)
val navController = findNavController(R.id.nav_host_fragment)
val appBarConfiguration = AppBarConfiguration(
setOf(
R.id.navigation_quizzes,
R.id.navigation_dashboard
)
)
setupActionBarWithNavController(navController, appBarConfiguration)
navView.setupWithNavController(navController)
}
override fun onBackPressed() {
doubleBackToExit()
}
}
DashboardItemListAdapter.kt
package com.example.quiz.ui.adapters
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.example.quiz.R
import com.example.quiz.models.Quiz
import kotlinx.android.synthetic.main.item_list_layout.view.*
open class DashboardItemsListAdapter(
private val context: Context,
private var list: ArrayList<Quiz>
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var onClickListener: OnClickListener? = null
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_dashboard_layout,
parent,
false
)
)
}
@SuppressLint("SetTextI18n")
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val model = list[position]
if (holder is MyViewHolder) {
holder.itemView.tv_quiz_name.text = model.quiz_name
holder.itemView.tv_participants.text = model.num_participants
holder.itemView.tv_questions.text = model.num_questions
holder.itemView.tv_duration.text = model.duration
holder.itemView.setOnClickListener {
if (onClickListener != null) {
onClickListener!!.onClick(position, model)
}
}
}
}
override fun getItemCount(): Int {
return list.size
}
fun setOnClickListener(onClickListener: OnClickListener) {
this.onClickListener = onClickListener
}
interface OnClickListener {
fun onClick(position: Int, product: Quiz)
}
class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
}
QuizListAdapter.kt
package com.example.quiz.ui.adapters
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.example.quiz.R
import com.example.quiz.models.Quiz
//import com.example.Quiz.utils.GlideLoader
import kotlinx.android.synthetic.main.item_list_layout.view.*
open class QuizListAdapter(
private val context: Context,
private val list: ArrayList<Quiz>,
) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_list_layout,
parent,
false
)
)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val model = list[position]
if (holder is MyViewHolder) {
holder.itemView.tv_quiz_name.text = model.quiz_name
holder.itemView.tv_participants.text = model.num_participants
holder.itemView.tv_questions.text = model.num_questions
holder.itemView.tv_duration.text = model.duration
}
}
override fun getItemCount(): Int {
return list.size
}
class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
}
DashboardFragment.kt
package com.example.quiz.ui.fragments
import android.os.Bundle
import android.util.Log
import android.view.*
import androidx.recyclerview.widget.GridLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.DashboardItemsListAdapter
import kotlinx.android.synthetic.main.fragment_dashboard.*
class DashboardFragment : BaseFragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dashboard, container, false)
}
override fun onResume() {
super.onResume()
getDashboardItemsList()
}
private fun getDashboardItemsList() {
showProgressDialog("please_wait")
FirestoreClass().getDashboardItemsList(this@DashboardFragment)
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
hideProgressDialog()
for (i in dashboardItemsList) {
Log.i("Item Title", i.quiz_name)
}
if (dashboardItemsList.size > 0) {
rv_dashboard_items.visibility = View.VISIBLE
tv_no_dashboard_items_found.visibility = View.GONE
rv_dashboard_items.layoutManager = GridLayoutManager(activity, 1)
rv_dashboard_items.setHasFixedSize(true)
val adapter = DashboardItemsListAdapter(requireActivity(), dashboardItemsList)
rv_dashboard_items.adapter = adapter
} else {
rv_dashboard_items.visibility = View.GONE
tv_no_dashboard_items_found.visibility = View.VISIBLE
}
}
}
使用上面的代码，我的应用程序在登录输入用户名和密码后崩溃，但是当我删除 rv_dashboard_items.adapter = adapter 至少应用程序不会崩溃。但是，它根本不显示来自 Firestore 的任何数据。
当我 运行 没有 rv_dashboard_items.adapter = adapter
以下代码段中的消息为红色。
E/DashboardFragment: [DocumentSnapshot{key=quizzes/C8STnkYwp3cYWMxm1Y0xQWERTZq1, metadata=SnapshotMetadata{hasPendingWrites=false, isFromCache=false}, doc=Document{key=quizzes/C8STnkYwp3cYWMxm1Y0xQWERTZq1, version=SnapshotVersion(seconds=1621955183, nanos=678854000), type=FOUND_DOCUMENT, documentState=SYNCED, value=ObjectValue{internalValue=# com.google.firestore.v1.Value@1abc2d14
integer_value: 0
map_value {
fields {
key: "quiz_id"
value {
integer_value: 0
string_value: "C8STnkYwp3cYWMxm1Y0xQWERTZq1"
}
}
fields {
key: "num_questions"
value {
integer_value: 0
string_value: "10"
}
}
fields {
key: "quiz_name"
value {
integer_value: 0
string_value: "Easy Quiz"
}
}
fields {
key: "duration"
value {
integer_value: 0
string_value: "10"
}
}
fields {
key: "num_participants"
value {
integer_value: 0
string_value: "5"
}
}
fields {
key: "user_id"
value {
integer_value: 0
string_value: "C8STnkYwp3cYWMxm1Y0xQWERTZq1"
}
}
}}}}]
还有这一行
E/RecyclerView: No adapter attached; skipping layout
QuizFragment.kt
package com.example.quiz.ui.fragments
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.QuizListAdapter
import kotlinx.android.synthetic.main.fragment_quiz.*
class QuizFragment : BaseFragment() {
private lateinit var mRootView: View
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
mRootView = inflater.inflate(R.layout.fragment_quiz, container, false)
return mRootView
}
fun successQuizListFromFireStore(quizList: ArrayList<Quiz>) {
hideProgressDialog()
if (quizList.size > 0) {
rvQuizzesFrag.visibility = View.VISIBLE
tv_no_products_found.visibility = View.GONE
rvQuizzesFrag.layoutManager = LinearLayoutManager(activity)
rvQuizzesFrag.setHasFixedSize(true)
val adapterQuizzes = QuizListAdapter(requireActivity(), quizList)
rvQuizzesFrag.adapter = adapterQuizzes
} else {
rvQuizzesFrag.visibility = View.GONE
tv_no_products_found.visibility = View.VISIBLE
}
}
private fun getQuizListFromFireStore() {
showProgressDialog("Please_wait")
FirestoreClass().getQuizList(this)
}
override fun onResume() {
super.onResume()
getQuizListFromFireStore()
}
}
activity_dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/nav_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="0dp"
android:layout_marginEnd="0dp"
android:background="@drawable/app_gradient_color_background"
app:itemIconTint="@color/colorWhite"
app:itemTextColor="@color/colorWhite"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:menu="@menu/bottom_nav_menu" />
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@id/nav_view"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/mobile_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>
fragment_dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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:background="@color/white"
tools:context=".ui.fragments.DashboardFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rv_dashboard_items"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tv_no_dashboard_items_found"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="no_dashboard_item_found"
android:textAlignment="center"
android:textSize="20sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
fragment_quiz.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
tools:context=".ui.fragments.QuizFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/rvQuizzesFrag"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tv_no_products_found"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:text="NO QUIZZES TODAY"
android:textAlignment="center"
android:textSize="30sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
FirestoreClass.kt
Import 部分代码已从问题中删除，因为我超出了问题中的字符限制。
package com.example.quiz.firestore
class FirestoreClass {
private val mFireStore = FirebaseFirestore.getInstance()
fun getDashboardItemsList(fragment: DashboardFragment) {
mFireStore.collection("quizzes")
.get()
.addOnSuccessListener { document ->
Log.e(fragment.javaClass.simpleName, document.documents.toString())
val quizList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val qz = i.toObject(Quiz::class.java)!!
qz.quiz_id = i.id
quizList.add(qz)
}
fragment.successDashboardItemsList(quizList)
}
.addOnFailureListener { e ->
fragment.hideProgressDialog()
Log.e(fragment.javaClass.simpleName, "Error while getting dashboard items list.", e)
}
}
fun getCurrentUserID(): String {
// An Instance of currentUser using FirebaseAuth
val currentUser = FirebaseAuth.getInstance().currentUser
var currentUserID = ""
if (currentUser != null) {
currentUserID = currentUser.uid
}
return currentUserID
}
fun uploadProductDetails(activity: AddProductActivity, productInfo: Quiz) {
mFireStore.collection("quizzes")
.document()
.set(productInfo, SetOptions.merge())
.addOnSuccessListener {
activity.productUploadSuccess()
}
.addOnFailureListener { e ->
activity.hideProgressDialog()
Log.e(
activity.javaClass.simpleName,
"Error while uploading the product details.",
e
)
}
}
fun getUserDetails(activity: Activity) {
mFireStore.collection("users")
.document(getCurrentUserID())
.get()
.addOnSuccessListener { document ->
Log.i(activity.javaClass.simpleName, document.toString())
val user = document.toObject(User::class.java)!!
val sharedPreferences =
activity.getSharedPreferences(
Constants.MYAPP_PREFERENCES,
Context.MODE_PRIVATE
)
val editor: SharedPreferences.Editor = sharedPreferences.edit()
editor.putString(
Constants.LOGGED_IN_USERNAME,
"${user.firstName} ${user.lastName}"
)
editor.apply()
when (activity) {
is LoginActivity -> {
activity.userLoggedInSuccess(user)
}
}
}
.addOnFailureListener { e ->
when (activity) {
is LoginActivity -> {
activity.hideProgressDialog()
}
}
Log.e(
activity.javaClass.simpleName,
"Error while getting user details.",
e
)
}
}
fun getQuizList(fragment: Fragment) {
mFireStore.collection("quizzes")
.whereEqualTo("user_id", getCurrentUserID())
.get()
.addOnSuccessListener { document ->
Log.e("Products List", document.documents.toString())
val productsList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val product = i.toObject(Quiz::class.java)
product!!.quiz_id = i.id
productsList.add(product)
}
when (fragment) {
is QuizFragment -> {
fragment.successQuizListFromFireStore(productsList)
}
}
}
.addOnFailureListener { e ->
when (fragment) {
is QuizFragment -> {
fragment.hideProgressDialog()
}
}
Log.e("Get Product List", "Error while getting product list.", e)
}
}
fun getAllQuizList(activity: Activity) {
mFireStore.collection("quizzes")
.get()
.addOnSuccessListener { document ->
Log.e("Products List", document.documents.toString())
val productsList: ArrayList<Quiz> = ArrayList()
for (i in document.documents) {
val product = i.toObject(Quiz::class.java)
product!!.quiz_id = i.id
productsList.add(product)
}
}
.addOnFailureListener { e ->
Log.e("Get Product List", "Error while getting all product list.", e)
}
}
}
看了你的代码，我觉得原因是：你的recycleView.
在你的代码中，你似乎在xml的同一个地方使用了两个recycleView，一个是没有数据的recycleView，另一个是recycleView 异步获取数据后。然后在获取数据的函数中控制recycleView的显示和隐藏？
但是，如果在将 recyclerview 附加到 Fragment 后不立即对其进行初始化，您可能会看到 No adapter attached; skipping layout。
解决方法：设置一个recycleView，在Fragment/activity的初始化函数中设置一个空数据给它。 DashboardItemsListAdapter(requireActivity(), listOf<Quiz>())
部分代码：
private lateinit var adapter: DashboardItemsListAdapter
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
adapter = DashboardItemsListAdapter(requestActivity(), arrayListOf<Quiz>())
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
adapter.list = dashboardItemsList
adapter.notifyDataSetChanged()
}
我只是在这里提供我的一个想法。您不能在每次调用 successDashboardItemsList() 时都设置新的适配器。在调用 successDashboardItemsList() 之前，您的适配器应该被初始化（可能没有数据）。每次调用 successDashboardItemsList() 时，
重新分配 Adapter 对象的列表字段的值。并调用Adapter对象的notifyDataSetChanged()，这样问题就解决了
import android.os.Bundle
import android.util.Log
import android.view.*
import androidx.recyclerview.widget.GridLayoutManager
import com.example.quiz.R
import com.example.quiz.firestore.FirestoreClass
import com.example.quiz.models.Quiz
import com.example.quiz.ui.adapters.DashboardItemsListAdapter
import kotlinx.android.synthetic.main.fragment_dashboard.*
class DashboardFragment : BaseFragment() {
private lateinit var adapter: DashboardItemsListAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setHasOptionsMenu(true)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_dashboard, container, false)
}
private lateinit var recyclerView: RecyclerView
private lateinit var textView: TextView
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
recyclerView = view.findViewById<RecyclerView>(R.id.rv_dashboard_items)
textView = view.findViewById(R.id.tv_no_dashboard_items_found)
adapter = DashboardItemsListAdapter(requireActivity(), arrayListOf<Quiz>())
recyclerView.layoutManager = GridLayoutManager(requireContext(), 1)
recyclerView.setHasFixedSize(true)
recyclerView.adapter = adapter
}
override fun onResume() {
super.onResume()
getDashboardItemsList()
}
private fun getDashboardItemsList() {
showProgressDialog("please_wait")
FirestoreClass().getDashboardItemsList(this@DashboardFragment)
}
fun successDashboardItemsList(dashboardItemsList: ArrayList<Quiz>) {
hideProgressDialog()
for (i in dashboardItemsList) {
Log.i("Item Title", i.quiz_name)
}
if (dashboardItemsList.size > 0) {
recyclerView.visibility = View.VISIBLE
textView.visibility = View.GONE
adapter.list = dashboardItemsList
adapter.notifyDataSetChanged()
} else {
recyclerView.visibility = View.GONE
textView.visibility = View.VISIBLE
}
}
}
DashboardItemListAdapter.kt
变为：
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return MyViewHolder(
LayoutInflater.from(context).inflate(
R.layout.item_list_layout,
parent,
false
)
)
}
在您的 DashboardItemsListAdapter 中，您正在膨胀 item_dashboard_layout 但您正在为 fragment_dashboard.
膨胀的布局可能不包含 fragment_dashboard 绑定所需的视图，因此绑定 returns 为空值。
确保您对膨胀和视图绑定使用相同的布局。