Develop Reference

Material Container Transform animation using floating action button not working smoothly

I am trying to open a fragment by clicking on floating action button using material container transform animation. I have implemented the animation but it is not working as I expected.
When navigating from one fragment A to Fragment B, the floating action button is still visible (enlarged for a brief second) when Fragment B is being opened.
What changes do I make in the animation so that the transition from floating action button to Fragment B feels more smooth? or How do I hide the enlarged floating action button when navigating to Fragment B?
Below is the code of Fragments and layouts for reference.
Fragment A layout:
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".ui.home.HomeFragment">
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/create_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:transitionName="my_transition"
android:src="#drawable/ic_round_add_24"
android:layout_gravity="bottom|end"
android:layout_margin="#dimen/dimen_16"
android:contentDescription="New Task"
</androidx.coordinatorlayout.widget.CoordinatorLayout>
Fragment A code:
class FragmentA : Fragment() {
private var _binding: FragmentABinding? = null
private val binding get() = _binding!!
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
exitTransition = Hold()
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentABinding.inflate(inflater)
binding.createTask.setOnClickListener {
val extras = FragmentNavigatorExtras(binding.createTask to "my_transition")
findNavController().navigate(R.id.action_FragmentA_to_FragmentB,null,null,extras)
}
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
Fragment B layout:
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:transitionName="my_transition"
tools:context=".ui.edit.EditTaskFragment">
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:layout_height="#dimen/toolbar_size"
app:liftOnScroll="true">
<FrameLayout
android:layout_width="match_parent"
android:paddingHorizontal="#dimen/dimen_16"
android:layout_height="match_parent">
<ImageButton
android:id="#+id/close"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/ic_baseline_close_24"
android:background="?attr/selectableItemBackgroundBorderless"
android:layout_gravity="start|center_vertical"
app:tint="?attr/colorPrimary" />
<com.google.android.material.button.MaterialButton
android:id="#+id/save"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|center_vertical"
style="#style/Widget.Material3.Button.TonalButton"
android:text="Save"
android:minWidth="0dp"
android:minHeight="0dp"/>
</FrameLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.core.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="#style/TextAppearance.Material3.HeadlineSmall"
android:textAlignment="center"
android:text="This is new Fragment"/>
</androidx.core.widget.NestedScrollView>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
Fragment B code:
class FragmentB : Fragment() {
private var _binding: FragmentBBinding? = null
private val binding get() = _binding!!
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
sharedElementEnterTransition = MaterialContainerTransform()
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
_binding = FragmentBBinding.inflate(inflater)
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}

Solved the problem!!
Just set startContainerColor and endContainerColor parameter in materialContainerTransform to surface color and then the fab transition is done more smoothly
Replace sharedElementEnterTransition in FragmentB with this:
sharedElementEnterTransition = MaterialContainerTransform().apply {
startContainerColor = requireContext().getColorFromAttr(com.google.android.material.R.attr.colorSurface)
endContainerColor = requireContext().getColorFromAttr(com.google.android.material.R.attr.colorSurface)
}

kotlin java.lang.NullPointerException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment

I looked at past questions but i can't still solve my problem
I am getting this error : java.lang.NullPointerException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment
My MainActivity code is :
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController =navHostFragment.navController
val navBottomView: BottomNavigationView = findViewById(R.id.bottomNavigation)
navBottomView.setupWithNavController(navController)
}
}
My HomeFragment code is this
class HomeFragment : Fragment() {
private var activity: MainActivity?= null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
activity = activity
}
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val view : View = inflater.inflate(R.layout.fragment_home,container,false)
return view
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
}
}
ActivityMain.xml code is here too :
<RelativeLayout 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"
android:paddingTop="?attr/actionBarSize">
<FrameLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="#id/app_bar_layout" >
<androidx.fragment.app.FragmentContainerView
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:navGraph="#navigation/nav_graoh" />
</FrameLayout>
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/app_bar_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true">
<androidx.appcompat.widget.Toolbar
android:id="#+id/dashboard_toolbar"
android:layout_width="match_parent"
android:layout_height="50dp"
android:background="#android:color/white">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/bottomNavigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/white"
app:menu="#menu/bottom_nav_menu"
app:labelVisibilityMode="unlabeled"
android:layout_marginRight="15dp"/>
</androidx.appcompat.widget.Toolbar>
</com.google.android.material.appbar.AppBarLayout>
I can't run my app. If some one can help me it will be perfect

The problem is in the MainActivity where you do not have setContentView(R.id.activity_main)
extra notes I have noticed
in your homeFragment you have:
activity = activity // which is self assign
and in your main activity xml you have a typo in the following line:
app:navGraph="#navigation/nav_graoh"
and you are missing the closing tag of relative layout

How to use Jetpack View Binding for Abstract Fragments

I have two fragments which have a lot in common. Therefore, I have an abstract fragment with an "abstract" layout file for this, which is included in the other two layout files.
However, I am not sure, how to use Jetpack View Binding for the abstract fragment, because I don't know which layout file is used.
Here a simplified example of my problem:
Abstract fragment (ExampleAbstractFragment.kt):
abstract class ExampleAbstractFragment : Fragment() {
override fun doSomething() {
val abstractTextView = findViewById<TextView>(R.id.abstract_text_view)
// ^^ How to get this with View Binding
val abstractButton = findViewById<Button>(R.id.abstract_button)
// ^^ How to get this with View Binding
}
}
Layout file of abstract fragment (fragment_example_abstract.xml):
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="#+id/abstract_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/test" />
<Button
android:id="#+id/abstract_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/test" />
</LinearLayout>
--
First fragment (ExampleFragmentA.kt):
class ExampleFragmentA : ExampleAbstractFragment() {
private var _binding: FragmentAExampleBinding? = null
private val binding get() = _binding!!
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
_binding = FragmentAExampleBinding?.inflate(inflater, container, false)
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
override fun doSomething() {
val textView = binding.fragmentAExampleTextView
val button = binding.fragmentAExampleButton
}
}
Layout file of first fragment (fragment_a_example.xml):
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="#+id/fragment_a_example_text_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/test" />
<include
layout="#layout/fragment_example_abstract"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/fragment_a_example_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/test" />
</LinearLayout>
--
Second fragment (ExampleFragmentB.kt):
class ExampleFragmentB : ExampleAbstractFragment() {
private var _binding: FragmentBExampleBinding? = null
private val binding get() = _binding!!
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
_binding = FragmentBExampleBinding?.inflate(inflater, container, false)
return binding.root
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
override fun doSomething() {
val editText = binding.fragmentBExampleEditText
val imageView = binding.fragmentBExampleImageView
}
}
Layout file of second fragment (fragment_b_example.xml):
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<EditText
android:id="#+id/fragment_b_example_edit_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/test" />
<include
layout="#layout/fragment_example_abstract"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<ImageView
android:id="#+id/fragment_b_image_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:src="#drawable/test" />
</LinearLayout>

Why is navigation destination lost when I launch a action for the second time with navigation in Android Studio?

I use navigation in my project.
The Image 1 will be displayed when the app start, I click Next button in Image 1, the Image 2 will be displayed, then I click Back button in Image 2, the image 1 will be displayed again.
Now I click Next button in Image 1 again, the app crash, I get the error 'navigation destination com.example.myapplication:id/actionTwo is unknown to this NavController', why?
Why can't NavHostFragment.findNavController(this).navigate(OneFrDirections.actionTwo()) be launched for the second time ?
You can download the test code at https://www.dropbox.com/s/1ad47eqi4iwig5v/MyNAV.zip?dl=0
my.xml
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/my"
app:startDestination="#+id/One">
<fragment
android:id="#+id/One"
android:name="com.example.myapplication.OneFr"
android:label="One">
<action
android:id="#+id/actionTwo"
app:destination="#id/Two" />
</fragment>
<fragment
android:id="#+id/Two"
android:name="com.example.myapplication.TwoFr"
android:label="Two">
<action
android:id="#+id/actionOne"
app:destination="#id/One" />
</fragment>
</navigation>
OneFr.kt
class OneFr : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?): View? =
inflater.inflate(R.layout.one, container, false)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
view.findViewById<Button>(R.id.btnNext).setOnClickListener {
NavHostFragment.findNavController(this).navigate(OneFrDirections.actionTwo())
}
}
}
TwoFr.kt
class TwoFr : Fragment() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?): View? =
inflater.inflate(R.layout.two, container, false)
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// Handle back button press
view.findViewById<Button>(R.id.btnBack).setOnClickListener {
fragmentManager?.popBackStack()
}
}
}
one.xml
<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">
<Button
android:id="#+id/btnNext"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Next"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
two.xml
<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">
<Button
android:id="#+id/btnBack"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Back"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
activity_main.xml
<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"
android:keepScreenOn="true"
tools:context=".MainActivity">
<fragment
android:id="#+id/fragment_container"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="#navigation/my" />
</FrameLayout>
MainActivity.kt
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
Image 1
Image 2

Instead of fragmentManager?.popBackStack() , try
NavHostFragment.findNavController(this).popBackStack()
Use NavigationController for back stack since NavController is managing navigation, manually popping fragments would cause errors in NavController.

Try the following for navigating:
From FrOne to FrTwo:
view.findNavController().navigate(R.id.actionTwo)
From FrTwo to FrOne:
view.findNavController().navigate(R.id.actionOne)

Setprogress for a progress bar across fragments android using Kotlin

I am an amateur to both, android studio and kotlin. I am implementing a scenario where I have some fragments, as and when we finish with one fragment, the progress is shown on the main layout. These fragments replace the main frame layout and switching from one fragment to next is done in the previous fragment using the setonclicklistener. However, the problem is that I am unable to see the update happening to the progressbar. By the way, I am not using any progress dialogue. All I need is to update the progress bar as I switch from one fragment to another. When I run the App, it doesn't crash but the update doesn't happen. The main_layout file as given below and the frame layout is replaced by the fragments.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<ProgressBar
android:id="#+id/parentmain_progress"
android:layout_width="match_parent"
android:layout_height="25dp"
style="#style/Base.Widget.AppCompat.ProgressBar.Horizontal"
android:scaleY="2"/>
<FrameLayout
android:id="#+id/parentmain_frame"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#id/parentmain_progress">
</FrameLayout>
</RelativeLayout>
One of the fragments where the progress is not updated:
class ParentChildInfoFragment : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_parent_info_relation, container, false)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
headerparentrelation_text?.text= arguments?.getString("name")
parentmain_progress?.max=4
parentmain_progress?.setProgress(3)
val string = "Your Cild is a....\n Girl/Boy"
specifying_relation_txt?.text = string
relation_mom_image?.setImageResource(R.drawable.girl)
relation_dad_image?.setImageResource(R.drawable.boy)
val girlstring = "Girl"
mom_txt?.text = girlstring
val boystring = "Boy"
dad_txt?.text=boystring
nextbtn_parentrelation.setOnClickListener {
fragmentManager?.beginTransaction()?.replace(R.id.parentmain_frame,ParentInfoFragment())?.commit()
}
}
}
Any help appreciated.

Like that ?
On this example I use the new package structure : Androidx
If you do not use it yet, simply change
import androidx.fragment.app.FragmentTransaction
by
import android.app.FragmentTransaction
You will find the code on this deposit :
https://github.com/Amadou19/Android-Multiple-fragment-with-progressBar---Kotlin.git
/****************************/
fragment1.xml
/****************************/
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#c15d5d">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="30sp"
android:text="Fragment 1"/>
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="Click Me"/>
</RelativeLayout>
/****************************/
Fragment1
/****************************/
class Fragment1 : Fragment() {
interface Fragment1Listner {
fun onClickFragment1()
}
var a1: Fragment1Listner? = null
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment1, container, false)
view.findViewById<Button>(R.id.button).setOnClickListener {
Toast.makeText(activity, "Clicked", Toast.LENGTH_SHORT).show()
a1?.onClickFragment1()
}
return view
}
}
/****************************/
fragment2.xml
/****************************/
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#5d80c1">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="30sp"
android:text="Fragment 2"/>
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="Click Me"/>
</RelativeLayout>
/****************************/
Fragment2
/****************************/
class Fragment2 : Fragment() {
interface Fragment2Listner {
fun onClickFragment2()
}
var a2: Fragment2Listner? = null
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment2, container, false)
view.findViewById<Button>(R.id.button2).setOnClickListener {
Toast.makeText(activity, "Clicked", Toast.LENGTH_SHORT).show()
a2?.onClickFragment2()
}
return view }
}
/****************************/
fragment3.xml
/****************************/
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#fab049">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="30sp"
android:text="Fragment 3"/>
</RelativeLayout>
/****************************/
Fragment3
/****************************/
class Fragment3 : Fragment() {
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater.inflate(R.layout.fragment3, container, false)
return view }
}
/****************************/
activity_main.xml
/****************************/
<?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"
android:orientation="vertical"
tools:context="com.example.amadoutirera.progressbar2.MainActivity">
<ProgressBar
android:id="#+id/progress_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="#style/Base.Widget.AppCompat.ProgressBar.Horizontal" />
<FrameLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="#+id/progress_bar"/>
</RelativeLayout>
/****************************/
MainActivity
/****************************/
class MainActivity : AppCompatActivity(), Fragment1.Fragment1Listner, Fragment2.Fragment2Listner {
lateinit var progressBar : ProgressBar
private lateinit var fragment1: Fragment1
private lateinit var fragment2: Fragment2
private lateinit var fragment3: Fragment3
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
/*------------------------------------------*/
progressBar = findViewById<ProgressBar>(R.id.progress_bar)
progressBar.max = 90
progressBar.progress = 30
/*------------------------------------------*/
fragment1 = Fragment1()
fragment2 = Fragment2()
fragment3 = Fragment3()
/*------------------------------------------*/
fragment1.a1 = this
fragment2.a2 = this
/*------------------------------------------*/
supportFragmentManager.beginTransaction()
.replace(R.id.container, fragment1)
.commit()
}
/*--------------- Onclik interface implementation -------------------*/
override fun onClickFragment1() {
supportFragmentManager.beginTransaction()
.replace(R.id.container, fragment2)
.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.addToBackStack(null)
.commit()
progressBar.incrementProgressBy(30)
}
override fun onClickFragment2() {
supportFragmentManager.beginTransaction()
.replace(R.id.container, fragment3)
.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.addToBackStack(null)
.commit()
progressBar.incrementProgressBy(30)
}
/*------------------------------------------*/
override fun onBackPressed() {
super.onBackPressed()
if(progressBar.progress ==60 || progressBar.progress ==90) progressBar.incrementProgressBy(-30)
}
}

try to Put your code in onCreateView() method.
Hope it works!!

Try
parentmain_progress?.post({
parentmain_progress?.progress = 3
})
instead of parentmain_progress?.setProgress(3)