Android Two-Way Databinding between multiple Tab Layouts in ViewPager2

Question

at the moment, i'm using single fragments or activities together with firebase ui and two-way databinding to display and edit my firestore data.

After downloading data from firebase in suspend fun, i call "binding.data = document".

Then i hide the ContentLoadingProgressBar and make the NestedScrollView visible.

After editing all textfields i collect the data with "Serializer().serialize(binding.data)" and forward it to my firebase upload service.

---

Now the question:

If i'm using ViewPager2 with TabLayout (see developer.android.com), how can i connect my firestore document to all "binding.data" of all tab fragments at the same time, so i can edit different parts of data in different tabs and collect them all at the end with "Serializer().serialize(binding.data)" to upload them?

---

Thanks in advance for your help!

Kotlin class containing data (compatible with Firestore up- and download)

package com.project.items.firestore

import android.text.format.DateFormat
import androidx.databinding.BaseObservable
import androidx.databinding.Bindable
import com.google.firebase.firestore.DocumentId
import com.google.firebase.firestore.Exclude
import com.project.BR
import java.util.*

class ArticleFirestoreDocument : BaseObservable() {
    companion object {
        fun build(
            id: String,
            ueberschrift: String,
            kategorie: String,
            zeit: Date,
            inhalt: String,
            links: ArrayList<String>,
            bilder: ArrayList<String>,
            visibility: String
        ): ArticleFirestoreDocument {
            val document = ArticleFirestoreDocument()
            document.id = id
            document.ueberschrift = ueberschrift
            document.kategorie = kategorie
            document.zeit = zeit
            document.inhalt = inhalt
            document.links = links
            document.bilder = bilder
            document.visibility = visibility
            return document
        }
    }

    @DocumentId
    @get:Bindable
    var id: String = ""
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.id)
            }
        }

    @get:Bindable
    var ueberschrift: String = ""
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.ueberschrift)
            }
        }

    @get:Bindable
    var kategorie: String = ""
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.kategorie)
            }
        }

    @get:Bindable
    var zeit: Date = Date()
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.zeit)
            }
        }

    @get:Bindable
    var inhalt: String = ""
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.inhalt)
            }
        }

    @get:Bindable
    var links: ArrayList<String> = arrayListOf()
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.links)
            }
        }

    @get:Bindable
    var bilder: ArrayList<String> = arrayListOf()
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.bilder)
            }
        }

    @get:Bindable
    var visibility: String = ""
        set(value) {
            if (field != value) {
                field = value
                notifyPropertyChanged(BR.visibility)
            }
        }

    fun getDateTime(date: Date?): String {
        return if (date != null) {
            val cal = Calendar.getInstance(TimeZone.getTimeZone("Europe/Berlin"))
            cal.time = date
            DateFormat.format("EEEE dd.MM.yyyy HH:mm", cal).toString() + " Uhr"
        } else {
            ""
        }
    }

    fun getDateTimeShort(date: Date?): String {
        return if (date != null) {
            val cal = Calendar.getInstance(TimeZone.getTimeZone("Europe/Berlin"))
            cal.time = date
            DateFormat.format("E dd.MM.yy HH:mm", cal).toString() + " Uhr"
        } else {
            ""
        }
    }

    fun getDate(date: Date?): String {
        return if (date != null) {
            val cal = Calendar.getInstance(TimeZone.getTimeZone("Europe/Berlin"))
            cal.time = date
            DateFormat.format("dd.MM.yyyy", cal).toString()
        } else {
            ""
        }
    }

    fun getTime(date: Date?): String {
        return if (date != null) {
            val cal = Calendar.getInstance(TimeZone.getTimeZone("Europe/Berlin"))
            cal.time = date
            DateFormat.format("HH:mm", cal).toString() + " Uhr"
        } else {
            ""
        }
    }

    @Exclude
    fun getEmojiText(): String {
        return ("${this.ueberschrift}\n\n" +
                "\uD83D\uDCC5 Datum: ${getDate(this.zeit)}\n" +
                "\uD83D\uDD50 Uhrzeit: ${getTime(this.zeit)}\n" +
                "\uD83D\uDDC3 Kategorie: ${this.kategorie}\n\n" +
                "\uD83D\uDCDD ${this.inhalt.replace("[ ]*\\\\n[ ]*".toRegex(), "\n").replace("\\\\t".toRegex(), "\t").trim()}\n\n" +
                this.links.joinToString(separator = "\n"))
            .trim()
    }
}

XML Layout (with data variable "ArticleFirestoreDocument" and two-way databinding, e.g. "@={data.kategorie}")

<?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">

    <data>

        <variable
            name="data"
            type="com.project.items.firestore.ArticleFirestoreDocument" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <include
            android:id="@+id/toolbar"
            layout="@layout/include_material_toolbar_edit"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <androidx.core.widget.NestedScrollView
            android:id="@+id/nsv"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:background="?attr/colorSurface"
            app:layout_behavior="@string/appbar_scrolling_view_behavior"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/toolbar">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:fitsSystemWindows="true"
                android:orientation="vertical">

                <include
                    android:id="@+id/visibility"
                    layout="@layout/include_material_textfield_clickable_icon"
                    app:hint="@{@string/hint_rule}"
                    app:icon="@{@drawable/ic_outline_rule_24}"
                    app:iconDescription="@{@string/icon_rule}"
                    app:text="@={data.visibility}" />

                <include
                    android:id="@+id/headline"
                    layout="@layout/include_material_textfield"
                    app:hint="@{@string/hint_headline}"
                    app:text="@={data.ueberschrift}" />

                <include
                    android:id="@+id/category"
                    layout="@layout/include_material_textfield_clickable_icon"
                    app:hint="@{@string/hint_category}"
                    app:icon="@{@drawable/ic_outline_category_24}"
                    app:iconDescription="@{@string/icon_category}"
                    app:text="@={data.kategorie}" />

                <include
                    android:id="@+id/content"
                    layout="@layout/include_material_textfield_icon"
                    app:hint="@{@string/hint_content}"
                    app:icon="@{@drawable/ic_outline_notes_24}"
                    app:iconDescription="@{@string/icon_notes}"
                    app:text="@={data.inhalt}" />

                <include
                    android:id="@+id/links"
                    layout="@layout/include_material_textfield_icon_end"
                    app:hint="@{@string/hint_link}"
                    app:icon="@{@drawable/ic_outline_link_24}"
                    app:iconDescription="@{@string/icon_link}"
                    app:iconEnd="@{@drawable/ic_outline_add_24}"
                    app:iconEndDescription="@{@string/icon_add}" />

                <include
                    android:id="@+id/links_recyclerview"
                    layout="@layout/include_material_recyclerview"
                    app:isBottom="@{false}"
                    app:isDivider="@{false}"
                    app:isFull="@{false}" />

                <include
                    android:id="@+id/pictures"
                    layout="@layout/include_material_textfield_clickable_icon"
                    app:icon="@{@drawable/ic_outline_photo_24}"
                    app:iconDescription="@{@string/icon_photo}"
                    app:text="@{@string/hint_images + @string/append_select}" />

                <include
                    android:id="@+id/pictures_recyclerview"
                    layout="@layout/include_material_recyclerview_horizontal"
                    app:isBottom="@{true}"
                    app:isDivider="@{false}"
                    app:isFull="@{true}" />
            </LinearLayout>
        </androidx.core.widget.NestedScrollView>

        <androidx.core.widget.ContentLoadingProgressBar
            android:id="@+id/clpb"
            style="?android:attr/progressBarStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:indeterminate="true"
            android:visibility="gone"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/toolbar" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>