I have an app that has MainActivity but all the work is in the fragment.
I made the fragment layout the HomePage using JetPack navigation. and it worked. but when i added the recycler view it crashed.
the error was this:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.saheralsous.android, PID: 12418
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.saheralsous.android/com.saheralsous.android.MainActivity}: android.view.InflateException: Binary XML file line #20 in com.saheralsous.android:layout/activity_main: Binary XML file line #20 in com.saheralsous.android:layout/activity_main: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: android.view.InflateException: Binary XML file line #20 in com.saheralsous.android:layout/activity_main: Binary XML file line #20 in com.saheralsous.android:layout/activity_main: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #20 in com.saheralsous.android:layout/activity_main: Error inflating class fragment
Caused by: java.lang.NullPointerException: null cannot be cast to non-null type androidx.recyclerview.widget.RecyclerView
at com.saheralsous.android.PhotoGalleryFragment.onCreateView(PhotoGalleryFragment.kt:45)
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.FragmentStore.moveToExpectedState(FragmentStore.java:112)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1647)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:3128)
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)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
at com.saheralsous.android.MainActivity.onCreate(MainActivity.kt:9)
at android.app.Activity.performCreate(Activity.java:8000)
E/AndroidRuntime: at android.app.Activity.performCreate(Activity.java:7984)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
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$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
I didn't add or change anything in the main activity
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
only in the activity_main i added the fragment for Navigation compnonent
<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=".MainActivity">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
i initialize the recyclerview in the fragment this way:
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
/**
* PagingDataAdapter
*/
RecyclerViewPhotoAdapter = RecyclerViewPhotoAdapter()
/**
* Recycler View
*/
PhotoRecyclerView =
view?.findViewById(R.id.recyclerview_main) as RecyclerView
PhotoRecyclerView.layoutManager = LinearLayoutManager(context)
//linking adapter with recyclerview
PhotoRecyclerView.adapter = RecyclerViewPhotoAdapter
/**
* Adapter, Repository and viewmodel
*/
pagingAdapter = PhotoPaging(
(requireActivity().application as MyApplication).networkApi
)
repository = GalleryFlowRepositoryImpl(pagingAdapter)
viewModel = ViewModelProvider(this, ViewModelProviderFactory(
PhotoGalleryViewModel::class
){
PhotoGalleryViewModel(repository)
}).get(PhotoGalleryViewModel::class.java)
//observing data
observers()
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_photo_gallery, container, false)
}
fragment_photo_gallery layout is simply this
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".PhotoGalleryFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerview_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
</FrameLayout>
I found problem in your code. You didn't inflate view before use RecyclerView.
PhotoRecyclerView = view?.findViewById(R.id.recyclerview_main) as RecyclerView
In there, view should be null. because you didn't inflate view. So to resolve your problem, there are two methods.
First, in onCreateView method you should inflate view before using.
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
var view = inflater.inflate(R.layout.fragment_photo_gallery, container, false)
/**
* PagingDataAdapter
*/
RecyclerViewPhotoAdapter = RecyclerViewPhotoAdapter()
/**
* Recycler View
*/
PhotoRecyclerView =
view?.findViewById(R.id.recyclerview_main) as RecyclerView
PhotoRecyclerView.layoutManager = LinearLayoutManager(context)
//linking adapter with recyclerview
PhotoRecyclerView.adapter = RecyclerViewPhotoAdapter
/**
* Adapter, Repository and viewmodel
*/
pagingAdapter = PhotoPaging(
(requireActivity().application as MyApplication).networkApi
)
repository = GalleryFlowRepositoryImpl(pagingAdapter)
viewModel = ViewModelProvider(this, ViewModelProviderFactory(
PhotoGalleryViewModel::class
){
PhotoGalleryViewModel(repository)
}).get(PhotoGalleryViewModel::class.java)
//observing data
observers()
// Inflate the layout for this fragment
return view
}
Or Second, you can use your code in onViewCreated method.