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Cannot hide back button on action bar

My application have two top level fragment A and B controlled by a bottom navigation bar and fragment C can be navigated only from fragment B. I don't want the action bar on fragment C shows back button while it cannot be hidden by setDisplayShowHomeEnabled() or setDisplayHomeAsUpEnabled()
How can I hide the back button?
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val navController = findNavController(R.id.navHostFragment)
val appBarConfiguration = AppBarConfiguration(
setOf(R.id.aFragment, R.id.bFragment)
)
setupActionBarWithNavController(navController, appBarConfiguration)
binding.navView.setupWithNavController(navController)
}
}

Try to set home fragment destination
var navHostFragment = supportFragmentManager
.findFragmentById(R.id.container) as NavHostFragment
var mNavController = navHostFragment.findNavController()
override fun onSupportNavigateUp(): Boolean {
return when (mNavController.currentDestination?.id) {
R.id.homeFrg -> {
true
}
else -> mNavController.navigateUp()
}
}

How to change fragment after a certain time?

My application consists of 3 main screens (fragments that switch between themselves bottom navigation).
Launching the app opens the Home screen (shown in code)
The question is the following. I want to add a welcome snippet that will run the very first one, where I'll make an animation and write something like "Hi, I'm an application!".
How can I make this fragment run first, and most importantly, how can I set it a time, for example 3 seconds, after which the Home fragment will start (that is, it will go to the fragment that I have right now when I start the application)?
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
var binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
replaceFragment(HomeFragment())
binding.bottomNavigationView.setOnItemSelectedListener { item ->
when(item.itemId) {
R.id.home -> {
replaceFragment(HomeFragment())
true
}
R.id.profile -> {
replaceFragment(ProfileFragment())
true
}
R.id.settings -> {
replaceFragment(SettingsFragment())
true
}
else -> false
}
}
}
private fun replaceFragment(fragment: Fragment){
val transaction = supportFragmentManager.beginTransaction()
transaction.replace(R.id.frame_layout, fragment)
transaction.commit()
}
}

Use this code change time (3000, 1000) according to your requeirment
var countDownTimer = object : CountDownTimer(30000, 1000) {
override fun onTick(millisUntilFinished: Long) {
}
override fun onFinish() {
//Replace fragment method here
}
}.start()

onItemSelectedListener for bottomnavigationbar

I am new to android and Kotlin, developing a bottom navigation bar using onitemselectedListener, since setOnNavigationItemSelectedListener is deprecated and I couldn't find any youtube tutorial that explains how to used onitemselectedlistener for navigationbar. navigation shows up on the emulator, but fragments are not showing up when i click on navigation Icons. here are my codes.
adding image of activity_main and emulator error image
fragmentWord image, that is connected to the first icon of "A" but doesn't show up
MainActivity
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.fragment.app.Fragment
import com.aryanvedh.vocabapp2.databinding.ActivityMainBinding
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val wordFragment = WordFragment()
val memorisedFragment = MemorisedFragment()
setCurrentFragment(wordFragment)
binding.bottomNavigationView.setOnItemSelectedListener { item ->
when (item.itemId) {
R.id.words -> setCurrentFragment(wordFragment)
R.id.memorised -> setCurrentFragment(memorisedFragment)
}
true
}
}
private fun setCurrentFragment(fragment: Fragment) =
supportFragmentManager.beginTransaction().apply {
replace(R.id.flFragment, fragment)
commit()
}
}```
any help? thanks

Use the function like this:
val navBar = findViewById<NavigationBarView>(R.id.navBar)
navBar.setOnItemSelectedListener {
when(it.itemId) {
R.id.item01 -> {
setCurrentFragment(Fragment01())
true
}
R.id.item02 -> {
setCurrentFragment(Fragment02())
true
}
R.id.item03 -> {
setCurrentFragment(Fragment03())
true
}
else -> {
false
}
}
}
It now should raise the fragments when each navigation bar item is selected.

You need to use the OnNavigationItemSelectedListener Method to capture once the item is selected in Bottom Navigation.
Here is the sample code attached from Documentation.
BottomNavigationView.OnNavigationItemSelectedListener { item ->
when(item.itemId) {
R.id.item1 -> {
// Respond to navigation item 1 click
true
}
R.id.item2 -> {
// Respond to navigation item 2 click
true
}
else -> false
}
}
Please refer to the Official Documentation for more information about BottomNavigationView.

how to put 2 different Fragments in a BottomNavigationView?

I try to put a BottomNavigationView like this in my main Activity, and I have a recycler view too :
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
loadFragment(HomeFragment(this))
//import the bottomNavigationView
val navigationView = findViewById<BottomNavigationView>(R.id.barre_nav)
navigationView.setOnNavigationItemSelectedListener {
when(it.itemId) {
R.id.nav_home -> {
loadFragment(HomeFragment(this))
return#setOnNavigationItemSelectedListener true
}
R.id.nav_choose -> {
loadFragment(ChooserFragment(ChooserActivity()))
return#setOnNavigationItemSelectedListener true
}
else -> false
}
}
}
private fun loadFragment(fragment: Fragment) {
val transactionMuscle = supportFragmentManager.beginTransaction()
transactionMuscle.replace(R.id.fragment_container, fragment)
transactionMuscle.addToBackStack(null)
transactionMuscle.commit()
}
But my problem with this code which is fine if I would to put the two view in the same container, but I wouldn't, is : I have a ChooserActivity and I would the second part of my bottomNavigationView to redirect to this page, and not the MainActivity Fragment with the Chooser composant. I would do the same as it do for the main Activity but with the ChooserActivity.
I doesn't know if I am clear, but I Thank you in advance.
EDIT to clarify :
My aim is to with mybottomNavigationView, when we click on the first button, it redirect to the MainActivity, and when we click on the second button, it redirect to the ChooserActivity. Th two must have there own containers. Hopefully it is better...

Solution
try this code:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val bottomNavigation: BottomNavigationView = findViewById(R.id.barre_nav)
bottomNavigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener)
} //onCreate() end here
private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item ->
when (item.itemId) {
R.id.nav_home -> {
val homeFragment = HomeFragment.newInstance()
loadFragment(homeFragment)
return#OnNavigationItemSelectedListener true
}
R.id.nav_choose -> {
val chooserFragment = ChooserFragment.newInstance()
loadFragment(chooserFragment)
return#OnNavigationItemSelectedListener true
}
}
false
}
private fun loadFragment(fragment: Fragment) {
val transactionMuscle = supportFragmentManager.beginTransaction()
transactionMuscle.replace(R.id.fragment_container, fragment)
transactionMuscle.addToBackStack(null)
transactionMuscle.commit()
}
In You Fragments OnCreateView() Method add these lines too :
1.HomeFragment
companion object {
fun newInstance(): HomeFragment = HomeFragment()
}
2.ChooserFragment
companion object {
fun newInstance(): ChooserFragment= ChooserFragment()
}
Hope so it works :)
If you still face any issue , please add it into comments

Disable multiple instance of fragment

In my main activity when user clicks button it shows him specific fragment. But if he clicks it again it adds another instance to backstack. And then the user needs to click back many times as click on the button.
class AppActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_app)
SharedPreferenceHelper.init(this)
GRPCClient.init(this)
DataBaseHelper.init(this)
imageViewDot.setOnClickListener {
findNavController(this, R.id.navHostFragmentApp).navigate(R.id.syncFragment)
}
}}
How can I prevent it from happening. What I need to do is if fragment is visible the button will not do anything.

try to flag that you already added this fragment and don't do that again
class AppActivity : AppCompatActivity() {
var navigated: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_app)
SharedPreferenceHelper.init(this)
GRPCClient.init(this)
DataBaseHelper.init(this)
imageViewDot.setOnClickListener {
if(navigated) return
findNavController(this, R.id.navHostFragmentApp).navigate(R.id.syncFragment)
navigated = true
}
}
override fun onBackPressed() {
super.onBackPressed() // removes from back stack if present in there
navigated = false
}
}
or you can use getBackStackEntry or getCurrentBackStackEntry from NavController instance to check that this Fragment is already on the position