UI blinking after pressing refresh

Issue

I have a fragment where I'm processing data from xml source, and everything is working fine, but the thing is when I refresh my layout by detaching and then attaching my fragment, the ui keeps blinking until all data is processed, I checked my code many time but I feel lost and I couldn't find anything

• This is how i'm processing my xml source data

fun getData(){
           val url = URL("www.xmldatasource.com")
           val factory = XmlPullParserFactory.newInstance()
           factory.isNamespaceAware = false
           val xpp = factory.newPullParser()
           xpp.setInput(GetInputStream(url), "utf-8")
           var insideItem = false
           var eventType = xpp.eventType
           while (eventType != XmlPullParser.END_DOCUMENT) {
               if (eventType == XmlPullParser.START_TAG) {
                   if (xpp.name.equals("item", ignoreCase = true)) {
                       insideItem = true
                   } else if (xpp.name.equals("title", ignoreCase = true)) {
                       if (insideItem) {
                           title = xpp.nextText()
                       }
                   } else if (xpp.name.equals("pubDate", ignoreCase = true)) {
                       if (insideItem) {
                           val subbedDate = xpp.nextText()
                           publishDate = subbedDate.substring(0, 25)
                       }
                   } else if (xpp.name.equals("guid", ignoreCase = true)) {
                       if (insideItem) {
                           link = xpp.nextText()
                       }
                   } else if (xpp.name.equals("description", ignoreCase = true)) {
                       if (insideItem) {
                           val newsDescription = xpp.nextText()
                           if (newsDescription.contains("src") && newsDescription.contains("jpg")) {
                               imageUrl = newsDescription.substring(
                                   newsDescription.indexOf("src=") + 5,
                                   newsDescription.indexOf("jpg") + 3
                               )
                           }
                           if (newsDescription.contains("<BR>") && newsDescription.contains("</p>")) {
                               description =
                                   newsDescription.substring(
                                       newsDescription.indexOf("<BR>") + 4,
                                       newsDescription.indexOf("</p>")
                                   )
                           }
                       }
                   }
               } else if (eventType == XmlPullParser.END_TAG && xpp.name.equals("item", ignoreCase = 
                   true)) {
                   insideItem = false
                   imageUrl?.let {
                       //TODO : Getting Image Url And Convert it to Bitmap
                       val urlImg = URL(it)
                       val httpURLConnection = urlImg.openConnection() as HttpURLConnection
                       httpURLConnection.connect()
                       val inputStream = httpURLConnection.inputStream
                       val bitmap = BitmapFactory.decodeStream(inputStream)
                       CoroutineScope(Dispatchers.Main).launch{
                           xmlList?.clear()
                           val model = NewsModel(bitmap, title, description, publishDate!!, link!!)
                           xmlList?.add(model)
                           leagueViewModel.insertNews(model)
                           binding.newsrcycler.adapter = LeagueNewsAdapter(requireContext(), xmlList!!)
                           customType(requireActivity(), "left-to-right")
                               }

                           })
                         
                          
                       }

                   }
               }
               eventType = xpp.next()
           }
   }

• Thsi is how i'm refreshing my fragment

 override fun onOptionsItemSelected(item: MenuItem): Boolean {
      when (item.itemId) {
          R.id.refresh -> {
              if(Constants.checkConnectivity(requireContext())){
                  requireActivity().supportFragmentManager.beginTransaction().detach(this).attach(this).commit()
              } else {
                  requireContext().ShowToast(requireContext(),"Please Check Your Internet..")
              }
          }
       
      }
      return true
  }

• This is the layout containing all views of my adapter

 <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">
    <data>
        <variable
            name="listener"
            type="taki.eddine.premier.league.pro.uilisteners.RssListener" />
        <variable
            name="newsModel"
            type="taki.eddine.premier.league.pro.models.NewsModel" />
    </data>

    <androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:elevation="16dp"
        android:layout_marginStart="10dp"
        android:layout_marginEnd="10dp"
        android:layout_marginTop="10dp">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:background="?attr/selectableItemBackground"
            android:onClick="@{() -> listener.RssArticle(newsModel)}">


            <de.hdodenhof.circleimageview.CircleImageView
                android:layout_width="match_parent"
                android:layout_height="140dp"
                android:layout_margin="8dp"
                android:layout_marginTop="5dp"
                app:layout_constraintBottom_toTopOf="@+id/guideline7"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintVertical_bias="0.0"
                app:rssimg="@{newsModel.newsBanner}"/>

            <TextView
                android:id="@+id/newstitle"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="10dp"
                android:layout_marginTop="4dp"
                android:layout_marginEnd="16dp"
                android:fontFamily="@font/andada"
                android:maxLines="2"
                android:text="@{newsModel.newsTitle}"
                android:textColor="@android:color/black"
                android:textSize="12sp"
                app:layout_constraintBottom_toTopOf="@+id/guideline14"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="@+id/guideline7"
                app:layout_constraintVertical_bias="0.0" />

            <TextView
                android:id="@+id/newsdescription"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginStart="10dp"
                android:layout_marginTop="4dp"
                android:layout_marginEnd="16dp"
                android:fontFamily="@font/adamina"
                android:maxLines="3"
                android:text="@{newsModel.newsDescription}"
                android:textColor="@android:color/black"
                android:textSize="12sp"
                app:layout_constraintBottom_toTopOf="@+id/guideline15"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="@+id/guideline14"
                app:layout_constraintVertical_bias="0.0" />
            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="50dp"
                android:orientation="horizontal">
                <de.hdodenhof.circleimageview.CircleImageView
                    android:layout_width="25dp"
                    android:layout_height="25dp"
                    android:layout_marginTop="11dp"
                    android:layout_marginStart="8dp"
                    android:src="@drawable/ic_baseline_date_range_24"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toStartOf="@+id/guideline22"
                    app:layout_constraintHorizontal_bias="0.842"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="@+id/guideline15" />

                <TextView
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="6dp"
                    android:layout_marginEnd="16dp"
                    android:fontFamily="@font/andada"
                    android:textStyle="bold"
                    android:textSize="11sp"
                    android:textColor="@android:color/holo_blue_dark"
                    android:layout_marginTop="15dp"
                    android:text="@{newsModel.newsDate}"
                    app:layout_constraintBottom_toBottomOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintStart_toStartOf="@+id/guideline22"
                    app:layout_constraintTop_toTopOf="@+id/guideline15" />
            </LinearLayout>
        </LinearLayout>
    </androidx.cardview.widget.CardView>

</layout>

• This is my fragment layout

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/newsprogress"
        android:visibility="visible"
        android:layout_gravity="center"/>

    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/newsrcycler"
        android:scrollbars="vertical"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>

Solution

You seem to be setting the RecyclerView adapter multiple times in the while loop. This will keep refreshing the RecyclerView.

You shouldn't be replacing the entire adapter, as the data changes. The data should be kept inside the adapter, and it should be updated inside the adapter.

How I got to this conclusion:

• getData() contains a while() loop.
• In this while loop, in the last branch you call CoroutineScope(Dispatchers.Main).launch {}
• In this launch {} you call binding.newsrcycler.adapter = LeagueNewsAdapter().

Answered By - Byte Welder