Develop Reference

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()
}
}

NavigationUI.setupActionBarWithNavController and setupActionBarWithNavController

I'm learning android development, Im looking up information about navigation components and fragments but I havent understood what is the diferent between
NavigationUI.setupActionBarWithNavController(this,navHostFragment.navController) and setupActionBarWithNavController(navController,appBarConfig).
bellow you can find two codes, In one Im using NavigationUI but In the other I dont.
First one:
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding= ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
NavigationUI.setupActionBarWithNavController(this,navHostFragment.navController)
binding.bnNavBar.setupWithNavController(navHostFragment.navController)
}
override fun onSupportNavigateUp(): Boolean {
val navController = this.findNavController(R.id.nav_host_fragment)
return navController.navigateUp()
}
}
Second one:
class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {
private lateinit var mainBinding: ActivityMainBinding
private lateinit var appBarConfiguration: AppBarConfiguration
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
mainBinding = ActivityMainBinding.inflate(layoutInflater)
setContentView(mainBinding.root)
val toolBar = mainBinding.activityMainContent.mainToolbar
//Setting up the tool bar as the app bar for the activity
setSupportActionBar(toolBar)
val host: NavHostFragment =
supportFragmentManager.findFragmentById(R.id.nav_host_fragment_container) as NavHostFragment
val navController = host.navController
//appBarConfiguration = AppBarConfiguration(navController.graph)
appBarConfiguration = AppBarConfiguration(
setOf(R.id.continentFragment),
mainBinding.drawerLayout
)
//First
setUpActionBar(navController,appBarConfiguration)
//Second
setUpNavigationView(navController)
}
private fun setUpActionBar(navController: NavController, appBarConfig : AppBarConfiguration) {
setupActionBarWithNavController(navController,appBarConfig)
}
private fun setUpNavigationView(controller: NavController) {
mainBinding.navView.setupWithNavController(controller)
}
override fun onNavigationItemSelected(item: MenuItem): Boolean {
mainBinding.drawerLayout.closeDrawer(GravityCompat.START)
return true
}
override fun onSupportNavigateUp(): Boolean {
val navController = findNavController(R.id.nav_host_fragment_container)
return navController.navigateUp(appBarConfiguration)|| super.onSupportNavigateUp()
}
override fun onBackPressed() {
if (mainBinding.drawerLayout.isDrawerOpen(GravityCompat.START)) {
mainBinding.drawerLayout.closeDrawer(GravityCompat.START)
} else {
super.onBackPressed()
}
}
}
Please, I'd be very thankful if someone can explain me the diference.
Ive read a lot about navigation but I havent found anything useful

Add custom layout to standard Toolbar

I want to add my custom layout to the side of the existing Toolbar, keeping all features with NavigationUI (Up button, animations, placing up buttons and drawers, etc)
How can i achieve this?

After some research i`ve found out the solution
MainActivity.kt
class MainActivity : AppCompatActivity() {
private val navController by lazy { findNavController(R.id.main_nav_host_fragment) }
private val appBarConfiguration by lazy { AppBarConfiguration(navController.graph) }
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val navController = this.findNavController(R.id.main_nav_host_fragment)
NavigationUI.setupActionBarWithNavController(this, navController)
NavigationUI.setupWithNavController(
findViewById<NavigationView>(R.id.navigation_view),
navController
)
}
override fun onSupportNavigateUp(): Boolean {
val navController = this.findNavController(R.id.main_nav_host_fragment)
return NavigationUI.navigateUp(navController, appBarConfiguration)
}
}
FragmentToolbar.kt interface
interface FragmentToolbar {
fun clearActionBar()
fun setCustomActionBar()
}
MainFragment.kt
Next class MainFragment.kt is abstract with methods clearActionBar() and setCustomActionBar() that can be overridden. They are defined in FragmentToolbar.kt interface, because if you set custom layout in first fragment, you will see it also in all other fragments. So, you will almost always have to clear your ActionBar and this class is responsible for standard realisation. setCustomActionBar() is up to you\
abstract class MainFragment : Fragment(), FragmentToolbar {
val actionBar: ActionBar? by lazy { (requireActivity() as AppCompatActivity).supportActionBar }
override fun clearActionBar() {
actionBar?.apply {
setDisplayShowCustomEnabled(false)
setDisplayShowTitleEnabled(true)
}
}
override fun setCustomActionBar() {}
}
MyFragment.kt
class MyFragment : MainFragment() {
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View {
clearActionBar() // defined in MainFragment
// Your code
}
override fun setCustomActionBar() {
actionBar?.apply {
setDisplayShowCustomEnabled(true)
setCustomView(R.layout.view_cart_and_bill)
}
actionBar?.customView?.apply { /* Here use findViewById to find necessary views inside your custom layout */ }
}
}
Hope my answer helps you. It also would be great, if ViewBinding could be used with this layout added in runtime, but i have not solved this issue yet

Nav component don't navigate from blocking screen's notification

I am receiving notification from firebase, it navigates correctly if receive it on foreground or background. But if I tap on notification from blocking screen it does not work. I think the problem is from not finding navController. But don't know what to do
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
setTheme(R.style.MainTheme)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main2)
mainviewModel.navigateToMainFragmentEvent.observe(this, EventObserver {
Log.d("A","notification")`
Navigation.findNavController(this, R.id.nav_host_fragment)
.navigate(R.id.action_global_mainFragment)
})
}
}
SplashFragment is a homeFragment
class SplashFragment : Fragment(R.layout.activity_splash) {
val splashViewModel: SplashViewModel by sharedViewModel()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
getStringExtra(NOTIFICATION_TYPE)?.let {
splashViewModel.notificationRecived(it)
}
}
}
when I debug this code:
Navigation.findNavController(this, R.id.nav_host_fragment)
IllegalStateException: ID does not reference a View inside this Activity

Why Nav Controller can't be declared as class variable?

I'm new to android and working through some tutorials. Currently working on implementing the Navigation controller and overriding the up button functionality. Part of doing this is to link the action bar with the Nav controller and overriding onSupportNavigateUp(). In doing this I noticed that we have to fetch the Nav Controller by id twice so I decided to create a class variable that does this and re-use the variable. The problem is the App crashes on startup when I do this. My guess is this is because I'm trying to get the Nav Controller before inflating the views?
So my question is why does this work:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
#Suppress("UNUSED_VARIABLE")
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
val navController = this.findNavController(R.id.myNavHostFragment)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
val navController = this.findNavController(R.id.myNavHostFragment)
return navController.navigateUp()
}
}
But this doesn't work:
class MainActivity : AppCompatActivity() {
private val navController = this.findNavController(R.id.myNavHostFragment)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
#Suppress("UNUSED_VARIABLE")
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
NavigationUI.setupActionBarWithNavController(this, navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}

You are right, you are assigning the navController before the view is inflated and passed the null to setupActionBarWithNavController
You can do it like this,
class MainActivity : AppCompatActivity() {
private lateinit var navController: NavController
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
#Suppress("UNUSED_VARIABLE")
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)
NavigationUI.setupActionBarWithNavController(this, navController)
navController = this.findNavController(R.id.myNavHostFragment)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp()
}
}