Develop Reference

Floating Action Button not visible over Mapbox Android

It has been a while since I have developed an Android app. So current dev work is pretty new for me. I am trying to create a Mapbox Android API based app. So far I have successfully loaded User location and move camera based on location change; however, the FAB I have added on the layout is not showing up in either emulator or my phone. It is visible in the XML design view. I believe it might be due to the setContentView(mapView) in MapsActivity.kt which I don't know how is it not able to load the whole layout. Am I missing anything?
activity_maps.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:mapbox="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<com.mapbox.maps.MapView
android:id="#+id/mapView"
android:layout_width="match_parent"
android:layout_height="match_parent"
mapbox:mapbox_cameraTargetLat="40.7128"
mapbox:mapbox_cameraTargetLng="-74.0060"
mapbox:mapbox_cameraZoom="9.0">
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:backgroundTint="#color/purple_200"
android:layout_margin="16dp"
android:contentDescription="#string/fab_description"
android:src="#drawable/ic_plus_icon"
tools:ignore="ImageContrastCheck" />
</com.mapbox.maps.MapView>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
MapsActivity.kt
package com.example.pinpoint
import android.Manifest
import android.content.pm.PackageManager
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.core.app.ActivityCompat
import com.example.pinpoint.com.example.pinpoint.LocationInitHelper
import com.example.pinpoint.com.example.pinpoint.LocationListeningCallback
import com.example.pinpoint.databinding.ActivityMapsBinding
import com.mapbox.android.core.location.LocationEngine
import com.mapbox.android.core.location.LocationEngineProvider
import com.mapbox.android.core.location.LocationEngineRequest
import com.mapbox.maps.CameraOptions
import com.mapbox.maps.MapView
import com.mapbox.maps.Style
import com.mapbox.maps.plugin.gestures.gestures
import com.mapbox.maps.plugin.locationcomponent.location
import java.lang.ref.WeakReference
class MapsActivity : AppCompatActivity() {
private lateinit var mapView: MapView
private lateinit var locationEngine: LocationEngine
private val callback = LocationListeningCallback(this)
private lateinit var locationPermissionHelper: LocationPermissionHelper
private lateinit var locationInitHelper: LocationInitHelper
private lateinit var binding: ActivityMapsBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMapsBinding.inflate(layoutInflater)
mapView = MapView(binding.root.context)
setContentView(mapView)
locationInitHelper = LocationInitHelper(WeakReference(this))
locationInitHelper.setMapView(mapView)
mapView.getMapboxMap().loadStyleUri(Style.MAPBOX_STREETS)
locationEngine = LocationEngineProvider.getBestLocationEngine(this)
locationPermissionHelper = LocationPermissionHelper(WeakReference(this))
onMapReady()
}
private fun onMapReady(){
val DEFAULT_INTERVAL_IN_MILLISECONDS = 1000L
val DEFAULT_MAX_WAIT_TIME = DEFAULT_INTERVAL_IN_MILLISECONDS * 5
locationEngine = LocationEngineProvider.getBestLocationEngine(this)
var request = LocationEngineRequest.Builder(DEFAULT_INTERVAL_IN_MILLISECONDS)
.setPriority(LocationEngineRequest.PRIORITY_NO_POWER)
.setMaxWaitTime(DEFAULT_MAX_WAIT_TIME)
.build()
if (ActivityCompat.checkSelfPermission(
this,
Manifest.permission.ACCESS_FINE_LOCATION
) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(
this,
Manifest.permission.ACCESS_COARSE_LOCATION
) != PackageManager.PERMISSION_GRANTED
) {
locationPermissionHelper.checkPermissions { onMapReady() }
}
locationEngine.requestLocationUpdates(request, callback, mainLooper)
locationEngine.getLastLocation(callback)
mapView.getMapboxMap().setCamera(
CameraOptions.Builder()
.zoom(12.0)
.build()
)
locationInitHelper.initLocationComponent()
locationInitHelper.setupGesturesListener()
}
override fun onRequestPermissionsResult(
requestCode: Int,
permissions: Array<String>,
grantResults: IntArray
) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults)
}
override fun onDestroy() {
super.onDestroy()
mapView.location
.removeOnIndicatorBearingChangedListener(locationInitHelper.onIndicatorBearingChangedListener)
mapView.location
.removeOnIndicatorPositionChangedListener(locationInitHelper.onIndicatorPositionChangedListener)
mapView.gestures.removeOnMoveListener(locationInitHelper.onMoveListener)
}
override fun onStop() {
super.onStop()
locationEngine.removeLocationUpdates(callback)
}
}

Try this
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
xmlns:mapbox="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<com.mapbox.maps.MapView
android:id="#+id/mapView"
android:layout_width="match_parent"
android:layout_height="match_parent"
mapbox:mapbox_cameraTargetLat="40.7128"
mapbox:mapbox_cameraTargetLng="-74.0060"
mapbox:mapbox_cameraZoom="9.0">
</com.mapbox.maps.MapView>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:backgroundTint="#color/purple_200"
android:layout_margin="16dp"
android:src="#drawable/ic_app_icon"
android:tint="#color/white"
tools:ignore="ImageContrastCheck" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

Try declaring the floating action button outside the mapview like this:
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:mapbox="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<com.mapbox.maps.MapView
android:id="#+id/mapView"
android:layout_width="match_parent"
android:layout_height="match_parent"
mapbox:mapbox_cameraTargetLat="40.7128"
mapbox:mapbox_cameraTargetLng="-74.0060"
mapbox:mapbox_cameraZoom="9.0"/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:backgroundTint="#color/purple_200"
android:layout_margin="16dp"
android:contentDescription="#string/fab_description"
android:src="#drawable/ic_plus_icon"
tools:ignore="ImageContrastCheck" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

I was able to solve this through MapsActivity.kt. As I suspected the setContentView() was getting the wrong view I replaced that part and assigned view manually to mapView. The script looks like this:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_maps)
mapView = findViewById(R.id.mapView)
locationInitHelper = LocationInitHelper(WeakReference(this))
locationInitHelper.setMapView(mapView)
mapView.getMapboxMap().loadStyleUri(Style.MAPBOX_STREETS)
locationEngine = LocationEngineProvider.getBestLocationEngine(this)
locationPermissionHelper = LocationPermissionHelper(WeakReference(this))
onMapReady()
}
Thanks for all the answers though!

How use View.OnClickListener with FirestoreRecyclerAdapter

I'm trying to create an application and considering my level it's not easy! I hope you could help me since I didn't succeed with the many links I found on the internet.
I can't add the onClick function of View.OnClickListener, each time the Intent function is not recognized. I tried to implement it in the UserViewHolder and FirestoreRecyclerAdapter class but it doesn't work.
Here is my current code:
---------- kotlin part ---------
package edu.stanford.rkpandey.emojistatus
import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.view.*
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.firebase.ui.firestore.FirestoreRecyclerAdapter
import com.firebase.ui.firestore.FirestoreRecyclerOptions
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.ktx.auth
import com.google.firebase.firestore.ktx.firestore
import com.google.firebase.ktx.Firebase
import kotlinx.android.synthetic.main.activity_main.*
data class User(
val displayName: String? = "",
val emojis: String? = ""
)
class UserViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)
class MainActivity : AppCompatActivity() {
private val db = Firebase.firestore
private lateinit var auth: FirebaseAuth
// Query the users collection
private val query = db.collection("users")
val options = FirestoreRecyclerOptions.Builder<User>()
.setQuery(query, User::class.java)
.setLifecycleOwner(this).build()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
auth = Firebase.auth
val adapter = object: FirestoreRecyclerAdapter<User, UserViewHolder>(options) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): UserViewHolder {
val view = LayoutInflater.from(this#MainActivity).inflate(R.layout.item_pack, parent, false)
return UserViewHolder(view)
}
override fun onBindViewHolder(
holder: UserViewHolder,
position: Int,
model: User
) {
val tvName: TextView = holder.itemView.findViewById(R.id.title)
val tvEmojis: TextView = holder.itemView.findViewById(R.id.excerpt)
tvName.text = model.displayName
tvEmojis.text = model.emojis
}
}
rvUsers.adapter = adapter
rvUsers.layoutManager = LinearLayoutManager(this)
}
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
menuInflater.inflate(R.menu.menu_main, menu)
return true
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
if (item.itemId == R.id.miLogout) {
Log.i("MainActivity", "Logout")
auth.signOut()
val logoutIntent = Intent(this, LoginActivity::class.java)
logoutIntent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
startActivity(logoutIntent)
}
return super.onOptionsItemSelected(item)
}
}
------- xml part -------
=> activity_main
<?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=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvUsers"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
=> item_pack
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="100sp"
xmlns:app="http://schemas.android.com/apk/res-auto">
<androidx.cardview.widget.CardView
android:id="#+id/card_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginStart="12sp"
android:layout_marginTop="12sp"
android:layout_marginEnd="12sp"
android:focusable="true"
android:clickable="true"
app:cardCornerRadius="10dp"
android:foreground="?android:attr/selectableItemBackground">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="10dp"
android:background="#color/colorPack">
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="5sp"
style="#style/NoteTitleFont"
android:textColor="#color/colorTitle"
tools:text="Note 1" />
<TextView
android:id="#+id/excerpt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="12sp"
android:layout_below="#id/title"
android:maxLines="1"
android:ellipsize="end"
android:textStyle="italic"
android:textColor="#color/colorDescribe"
tools:text="test text va se trouver ici, ça va contenir le début de la description du package." />
</RelativeLayout>
</androidx.cardview.widget.CardView>
</RelativeLayout>
This code gives this result :
I would like that when I click on one of the carviews it can go to the activity_pack_detail.
Do you know how to do Intent to PackDetailActivity?
I get this error no matter what I do =>

You're getting that error because you are calling Intent's class constructor with a wrong argument. The first argument should be a Context and not a View. The keyword this is referring in your code to a View and not to a context, hence the error.
To solve this, you have to pass a Context object like this:
val i = Intent(view.getContext(), PackDetailActivity::class.java)
And your error will go away.

Does View::invalidate redraw ervery child View?

I thought android had a diff mechanism to avoid redraw whole View tree when I invoke View::invalidate. Through checking the source code of View::invalidate, I find the invalidate
will propagate to ViewRootImpl and invoke ViewRootImpl::performTraversals. This method then draw whole view tree(except hardware acceleration enabled).
I try to find the code that View/ViewGroup can skip draw accroding dirty region, But I failed.Seems like erevry view will invoke onDraw
Below case, why does #id/frame_layout invoke onDraw when I change child #id/front backgroud color? Should't it refresh view locally?
layou.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:theme="#style/Theme.AppCompat.NoActionBar"
tools:context=".MainActivity">
<FrameLayout
android:id="#+id/frame_container"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintBottom_toBottomOf="#id/btn"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="#+id/layout_back"
android:background="#color/black"
android:layout_width="100dp"
android:layout_height="100dp"
/>
<FrameLayout
android:id="#+id/layout_front"
android:background="#color/white"
android:layout_width="100dp"
android:layout_height="100dp"
/>
</FrameLayout>
<com.google.android.material.button.MaterialButton
android:id="#+id/btn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="switch color"
app:layout_constraintBottom_toBottomOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
package com.flybutter.demo
import android.graphics.Color
import android.os.*
import android.util.Log
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import android.widget.Toast
import androidx.lifecycle.LifecycleObserver
import com.bumptech.glide.Glide
import com.flybutter.demo.databinding.ActivityMainBinding
private const val TAG = "MainActivity"
class MainActivity : AppCompatActivity() {
lateinit var binding: ActivityMainBinding
var c = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
binding.frameLayout.viewTreeObserver.addOnDrawListener {
Log.d(TAG, "onCreate: container ondraw")
}
binding.layoutFront.viewTreeObserver.addOnDrawListener {
Log.d(TAG, "onCreate: front on draw")
}
binding.layoutFront.viewTreeObserver.addOnDrawListener {
Log.d(TAG, "onCreate: back on draw")
Log.d(TAG,">>>>>>>>>>>>>>>>>>>")
}
binding.btn.setOnClickListener {
binding.layoutFront.setBackgroundColor( if (c) Color.WHITE else Color.GRAY)
c = !c
}
setContentView(binding.root)
}
}

RecyclerView functions aren't called

I am trying to show a list of transactions in a recycler view.
Each transaction is represented by a CardView inside a constraint layout (see item_transaction.xml).
Somehow, the functions of my RecyclerView Adapter (onCreateViewHolder, onBindViewHolder and getItemCount) are never called (logs are never displayed - I removed most of them so the code is easier to read).
Therefore, the RecyclerView content doesn't display on my app.
It is also worth pointing out that I have a list of transactions called data in my adapter. Whenever I set the data in the list, it does update. No issues there.
💡 I know notifyDataSetChanged() isn't clean, I'll change it later on when I manage to get everything working.
Here is a preview of what I want so you can grasp the idea better :
EDIT : My fragment displays normally and has no problem executing code.
Hang on tight because there is a lot of code :
package com.example.manage.manageit.database
class Transaction(
var value: Long = 0,
var note: String = "",
var budget: String = "",
var creationTime: Long = System.currentTimeMillis()
)
Transaction.kt
package com.example.manage.manageit.home
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import com.example.manage.manageit.databinding.ActivityHomeBinding
import androidx.fragment.app.Fragment
import com.example.manage.manageit.R
import com.example.manage.manageit.about.AboutFragment
import com.example.manage.manageit.budget.TransactionFragment
class HomeActivity : AppCompatActivity() {
private lateinit var binding: ActivityHomeBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = DataBindingUtil.setContentView(this, R.layout.activity_home)
binding.bottomNavigation.menu.getItem(0).isCheckable = true
setFragment(HomeFragment())
binding.bottomNavigation.setOnItemSelectedListener {menu ->
when(menu.itemId){
R.id.homeFragmentButton -> {
setFragment(HomeFragment())
true
}
R.id.transactionFragmentButton -> {
setFragment(TransactionFragment())
true
}
R.id.aboutFragmentButton -> {
setFragment(AboutFragment())
true
}
else -> false
}
}
}
private fun setFragment(fr : Fragment){
val frag = supportFragmentManager.beginTransaction()
frag.replace(R.id.myNavHostFragment,fr)
frag.commit()
}
}
HomeActivity.kt : It contains a BottomNavigationView and my fragment.
package com.example.manage.manageit.home
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.databinding.DataBindingUtil
import androidx.fragment.app.Fragment
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.manage.manageit.R
import com.example.manage.manageit.adapters.TransactionAdapter
import com.example.manage.manageit.database.Transaction
import com.example.manage.manageit.databinding.FragmentHomeBinding
import java.util.logging.Logger
class HomeFragment : Fragment() {
private var logger = Logger.getLogger(HomeFragment::class.java.name)
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val binding: FragmentHomeBinding = DataBindingUtil.inflate(
inflater,
R.layout.fragment_home,
container,
false
)
val recyclerView: RecyclerView = binding.transactionList
val transactionAdapter = TransactionAdapter()
recyclerView.adapter = transactionAdapter
recyclerView.layoutManager = LinearLayoutManager(context)
transactionAdapter.data = listOf(
Transaction(10, "Transaction note", "Groceries"),
Transaction(20, "Transaction note", "Groceries"),
Transaction(30, "Transaction note", "Groceries")
)
return inflater.inflate(R.layout.fragment_home, container, false)
}
}
HomeFragment.kt
package com.example.manage.manageit.adapters
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.manage.manageit.R
import com.example.manage.manageit.database.Transaction
import java.util.logging.Logger
class TransactionAdapter : RecyclerView.Adapter<TransactionViewHolder>() {
private var logger = Logger.getLogger(this::class.java.name)
var data = listOf<Transaction>()
set(value) {
field = value
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TransactionViewHolder {
logger.info("adapter : onCreateViewHolder()")
return TransactionViewHolder.from(parent)
}
override fun onBindViewHolder(holder: TransactionViewHolder, position: Int) {
val item = this.data[position]
holder.bind(item)
}
override fun getItemCount(): Int {
logger.info("adapter : getItemCount()")
return this.data.size
}
}
class TransactionViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val icon: ImageView = itemView.findViewById(R.id.transaction_icon)
private val note: TextView = itemView.findViewById(R.id.transaction_note)
private val value: TextView = itemView.findViewById(R.id.transaction_value)
fun bind(item: Transaction) {
icon.setImageResource(R.drawable.ic_dollar_sign)
note.text = item.note
value.text = item.value.toString()
}
companion object {
fun from(parent: ViewGroup): TransactionViewHolder {
val layoutInflater = LayoutInflater.from(parent.context)
val view = layoutInflater
.inflate(R.layout.item_transaction, parent, false)
return TransactionViewHolder(view)
}
}
}
TransactionAdapter.kt
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.manage.manageit.home.HomeActivity">
<RelativeLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.fragment.app.FragmentContainerView
android:id="#+id/myNavHostFragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"/>
</LinearLayout>
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:background="#android:color/black"
android:paddingVertical="6dp"
app:itemIconSize="28dp"
app:itemIconTint="#color/nav_bar_item"
app:itemRippleColor="#color/ripple_color"
app:itemTextColor="#color/nav_bar_item"
app:labelVisibilityMode="unlabeled"
app:menu="#menu/bottom_navigation_menu" />
</RelativeLayout>
</layout>
activity_home.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#android:color/black"
android:fillViewport="true"
tools:context="com.example.manage.manageit.home.HomeFragment">
<TextView
android:id="#+id/homeActivityTitle"
style="#style/activityTitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginStart="#dimen/medium_margin"
android:layout_marginTop="#dimen/medium_margin"
android:layout_marginEnd="#dimen/medium_margin"
android:text="#string/home_text"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/transaction_list"
android:layout_width="match_parent"
android:layout_height="400dp"
android:visibility="visible"
app:layout_constraintBottom_toTopOf="#+id/floatingActionButton"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/homeActivityTitle" />
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/floatingActionButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="#dimen/medium_margin"
android:layout_marginBottom="#dimen/very_big_margin"
android:backgroundTint="#color/secondaryColor"
android:clickable="true"
android:contentDescription="#string/add_button_description"
android:src="#drawable/ic_plus"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:maxImageSize="32dp"
tools:ignore="RedundantDescriptionCheck" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
fragment_home.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="wrap_content">
<androidx.cardview.widget.CardView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="20dp"
app:cardBackgroundColor="#android:color/transparent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="#drawable/transaction">
<ImageView
android:id="#+id/transaction_icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:contentDescription="Icon"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/ic_dollar_sign"
app:tint="#android:color/white" />
<TextView
android:id="#+id/transaction_note"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="30dp"
android:text="Transaction note"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toEndOf="#+id/transaction_icon"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/transaction_value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="30dp"
android:text="55€"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
</androidx.constraintlayout.widget.ConstraintLayout>
item_transaction.xml : Basically a card view with an image and two text views (the transaction "note" and value).

In onCreateView, you have created your view layout twice. The first one you did using DataBindingUtil and that's the one whose RecyclerView you set up. But then you let that whole layout go back to the garbage collector because you create a brand new layout using layoutInflater and return that layout on the last line of onCreateView.
Technically, you should not be setting up views in onCreateView anyway. It should be done in onViewCreated(), although I don't think it makes much difference. However, since Fragment provides a constructor that can automatically inflate a provided layout ID, I think it's cleaner anyway to eliminate onCreateView() entirely, like this:
class HomeFragment : Fragment(R.layout.fragment_home) {
private var logger = Logger.getLogger(HomeFragment::class.java.name)
override fun onViewCreated(
view: View,
savedInstanceState: Bundle?
) {
val binding: FragmentHomeBinding = DataBindingUtil.bind(view)
val recyclerView: RecyclerView = binding.transactionList
val transactionAdapter = TransactionAdapter()
recyclerView.adapter = transactionAdapter
recyclerView.layoutManager = LinearLayoutManager(context)
transactionAdapter.data = listOf(
Transaction(10, "Transaction note", "Groceries"),
Transaction(20, "Transaction note", "Groceries"),
Transaction(30, "Transaction note", "Groceries")
)
}
}

RecyclerView flickering line while scrolling

I'm working on my first Android app and implemented a RecyclerView to scroll through some items.
I followed the following Youtube Tutorial.
I'm using a Huawei P20 Pro (physical device) to test the program, and i noticed that there is a flickering line while scrolling through the items. (On the emulator, use a Google Pixel 3 and there is no noticeable flickering)
White flickering line that appears during scrolling
I implemented the adapter as:
package com.example.recyclerviewexample
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.test_3.R
import kotlinx.android.synthetic.main.example_item.view.*
class ExampleAdapter(private val exampleList: List<ExampleItem>) : RecyclerView.Adapter<ExampleAdapter.ExampleViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ExampleViewHolder {
val itemView = LayoutInflater.from(parent.context).inflate(
R.layout.example_item,
parent,
false)
return ExampleViewHolder(itemView)
}
override fun onBindViewHolder(holder: ExampleViewHolder, position: Int) {
val currentItem = exampleList[position]
holder.imageView.setImageResource(currentItem.imageResource)
holder.textView1.text = currentItem.text1
holder.textView2.text = currentItem.text2
}
override fun getItemCount() = exampleList.size
class ExampleViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val imageView: ImageView = itemView.image_view //image_view is the id of the image! (same: itemView.findViewById(R.id.image_view))
val textView1: TextView = itemView.text_view_1
val textView2: TextView = itemView.text_view_2
}
}
Also, i uploaded my code to Github so you can try it out yourself.
As I'm very new to android studio, I really have no clue what's going on and would highly appreciate your help.
Thanks :)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
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=".MaliActivity">
<include
android:id="#+id/toolbar_main"
layout="#layout/toolbar_mali"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_below="#+id/toolbar_main"
android:layout_height="wrap_content"
android:orientation="horizontal">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/search_list"
android:layout_width="399dp"
android:layout_height="633dp"
android:layout_below="#+id/searchView"
android:layout_margin="5dp"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />
</LinearLayout>
<androidx.appcompat.widget.SearchView
android:id="#+id/searchView"
android:layout_width="331dp"
android:layout_height="53dp"
android:layout_alignParentRight="true"
android:padding="10dp"
app:queryHint="Search for a resource ">
</androidx.appcompat.widget.SearchView>
</RelativeLayout>

Check out the Layout file. the match_parent on the Layout height property. Change it to wrap_content.
In my case the issue was each item in the recyclerview occupied the whole screen and this helped. It could be the same for you.