I am attempting to set a navHostFragment in my MainActivity.kt file, but the code below results in the error:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lunchtray/com.example.lunchtray.MainActivity}: java.lang.NullPointerException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment
class MainActivity : AppCompatActivity() {
private lateinit var navController: NavController
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val navHostFragment = supportFragmentManager // NULL CANNOT BE CAST TO NON NULL TYPE
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
navController = navHostFragment.navController
setupActionBarWithNavController(navController)
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp() || super.onSupportNavigateUp()
}
}
activity_main.xml layout file:
<androidx.constraintlayout.widget.ConstraintLayout
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">
<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/mobile_navigation"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
What am I doing wrong? Similar questions exist on SO but they involve using menu IDs or initializing the navHostFragment from within a fragment, this is a much more straightforward situation and I do not understand why any value should be null.
You forgot to call setContentView(R.layout.activity_main), which means you have no FragmentContainerView and no fragment within it, hence why findFragmentById(R.id.nav_host_fragment) returns null.
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
navController = navHostFragment.navController
As an alternative, you can also call the AppCompatActivity construct that takes a LayoutRes, which will automatically call setContentView for you as part of super.onCreate():
class MainActivity : AppCompatActivity(R.ayout.activity_main) {
Related
I am using nav component, just Activity Frag1,Frag2 , however moving from Frag1 to Frag2 is working, but When phone back button is pressed, Frag1 is appearing But nothing works, Clicklistner is nothing, init code does working
class CarActivity : AppCompatActivity() {
fun getLayoutId(): Int = R.layout.activity_car
private lateinit var appBarConfiguration: AppBarConfiguration
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(getLayoutId())
setSupportActionBar(toolbar_details)
val navController = findNavController(R.id.nav_host_fragment_content_main)
appBarConfiguration = AppBarConfiguration(navController.graph)
setupActionBarWithNavController(navController, appBarConfiguration)
}
}
Activity
<fragment
android:id="#+id/nav_host_booking_fragment_content_main"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="#navigation/nav_graph" />
nav_graph.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"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/nav_graph_cars"
app:startDestination="#id/carFragment">
<fragment
android:id="#+id/Frag1"
android:label=" ">
in activity
override fun onSupportNavigateUp(): Boolean {
val navController = findNavController(R.id.nav_host_fragment_content_main)
return navController.navigateUp(appBarConfiguration)
|| super.onSupportNavigateUp()
}
is seems like a new view is created, or a view is disconnected from fragment
using ViewBinding solve everything but ?
I am using Navigation Component for navigating in my app. It works fine inside fragments but it fails to find the nav host in the activity that holds the actual navigation host.
I am trying to open a new fragment when the user clicks on FAB, which I included in Main activity's XML. When I call findNavController() it fails to find the controller. The nav host controller is in the XML layout. I can't understand why it fails to find it.
MainActivity
class MainActivity : AppCompatActivity(), OnActivityComponentRequest {
override fun getTabLayout(): TabLayout {
return this.tabLayout
}
override fun getFap(): FloatingActionButton {
return this.floatingActionButton
}
private lateinit var tabLayout: TabLayout
private lateinit var floatingActionButton: FloatingActionButton
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
fab.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
}
Activity main XML
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
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"
tools:context=".domain.MainActivity"
android:animateLayoutChanges="true">
<com.google.android.material.appbar.AppBarLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:theme="#style/AppTheme.AppBarOverlay">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay"/>
<com.google.android.material.tabs.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.tabs.TabItem
android:text="Test 1"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
<com.google.android.material.tabs.TabItem
android:text="Test 2"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
</com.google.android.material.tabs.TabLayout>
</com.google.android.material.appbar.AppBarLayout>
<fragment
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/main_navigation" />
<com.google.android.material.bottomappbar.BottomAppBar
android:id="#+id/bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_anchorGravity="right|top"
app:layout_anchor="#+id/bar"
android:src="#drawable/ic_add_black_24dp"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
I was getting the same exeception until I managed to get the navController this way:
val navHostFragment = supportFragmentManager.findFragmentById(R.id.my_fragment_container_view_id) as NavHostFragment
val navController = navHostFragment.navController
Obtained from this answer:
Before finding the nav controller, you need to set the view, if you are using binding:
binding = BaseLayoutBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
If not:
setContentView(R.layout.activity_main)
Use the corresponding binding for fragments.
Try setting up onClickListener of Fab button in onStart of the Activity as in onCreate Activity is just inflating the View and haven't set the NavHostController. So if you setup onClickListener in onStart of activity is will work as expected.
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
}
override fun onStart() {
super.onStart()
floatingActionButton.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
In Java you can find NavController inside activity this way:
Navigation.findNavController(this,R.id.nav_host).navigate(R.id.YourFragment);
The problem might be that FAB was added to the activity or a fragment different from the one used by NavHost fragment. In this case, when you call it.findNavController() it cannot find the navigation controller.
You can either check that your FAB belongs to the fragment pulled by NavHost or call an Activity's findNavController(<id>) and pass it id of the fragment you're looking up
override fun onCreate(savedInstanceState: Bundle?) {
...
fab.setOnClickListener {
findNavController(R.id.nav_host_fragment)
.navigate(R.id.addNewWorkoutFragment)
}
}
Retrieve it later, in onPostCreate. like this:
#Override
public void onPostCreate(Bundle savedInstanceState ) {
super.onPostCreate(savedInstanceState);
navController = Navigation.findNavController(this, R.id.fragment_container_view);
}
Turns out that activity that holds navigation controller... doesn't have navigation component.
The solution is to manually set the NavController to each view contained in the activity.
val navController = findNavController(R.id.nav_host_fragment)
Navigation.setViewNavController(fab, navController)
Now this would work:
fab.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
I still don't understand why this works the way it works so any explanation would be more than welcome :)
As of now, Android API simply doesn't make much sense.
Source: Navigate to fragment on FAB click (Navigation Architecture Components)
Kotlin Only
Android Navigation KTX provides an extension function for Activity
All I had to do was
findNavController(R.id.myNavHostFragment).navigate(R.id.to_someFragment)
I do have the following dependencies in my app/gradle.build.kts file (
implementation ("androidx.navigation:navigation-fragment-ktx:2.3.5")
implementation ("androidx.navigation:navigation-runtime-ktx:2.3.5")
implementation ("androidx.navigation:navigation-ui-ktx:2.3.5")
Using Directions
Alternatively you could also use generated Directions class. Since this is a global action the Directions class is found in the NavigationDirections.to_someFragment()
//very useful if you're passing args then you could do something like
//NavigationDirections.to_someFragment(myArg)
NavigationDirections.to_someFragment()findNavController(R.id.myNavHostFragment).navigate(NavigationDirections.to_someFragment())
Side-note the specific extension function is being contributed from the runtime-ktx aar
you can still get access in your oncreate by doing
//the id would be the id of the Fragment Element In Your Activity XML File
val navGraph = Navigation.findNavController(this, R.id.activity_main)
binding.mainFab.setOnClickListener {
navGraph.navigate(R.id.destinationFragment)
}
I found this answer helpful. In your activity paste this code
Navigation.findNavController(this, R.id.nav_host_fragment).navigate(R.id.yourDestination)
This is Extension version for Kotlin:
fun AppCompatActivity.findNavController(
#IdRes navHostViewId: Int
): NavController {
val navHostFragment =
supportFragmentManager.findFragmentById(navHostViewId) as NavHostFragment
return navHostFragment.navController
}
The navHostViewId is id of your androidx.fragment.app.FragmentContainerView.
The best way to access navController in OnCreate of Activity is to access it after inflating the layout
that can achieved by kotlin extention function doOnPreDraw()
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private val navController: NavController
get() = Navigation.findNavController(this, R.id.nav_host_fragment)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.root.doOnPreDraw {
// here you can safely use navController
binding.toolbar.setupWithNavController(navController)
}
}
}
You can use binding.root.findNavController().navigate(id)
I have the following code:
activity_reminders.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"
tools:context=".locationreminders.RemindersActivity">
<fragment
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_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
ReminderActivity.kt
class RemindersActivity : AppCompatActivity() {
private lateinit var binding: ActivityRemindersBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityRemindersBinding.inflate(layoutInflater)
setContentView(binding.root)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
when (item.itemId) {
android.R.id.home -> {
(binding.navHostFragment as NavHostFragment).navController.popBackStack()
return true
}
}
return super.onOptionsItemSelected(item)
}
}
binding.navHostFragment in unresolved and i don't understand why, if i change the type of view in anything differnt then "fragment" the view binding works.
Is possible to use view vbinding for a fragment inside another view?
I found the following as a workaround solution to get the fragment.
val navHostFragment = findNavController(R.id.nav_host_fragment)
navHostFragment.popBackStack()
I think that is not possible to use view binding with a <fragment> because fragment is not a descendent of View.
Instead of:
(binding.navHostFragment as NavHostFragment).navController.popBackStack()
Use the following code:
(supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment).navController.popBackStack()
I have one activity and few fragments. I set up my activity with NavController and navigation graph like this:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_activity_main) as NavHostFragment
navController = navHostFragment.findNavController()
}
override fun onSupportNavigateUp(): Boolean {
return navController.navigateUp() || super.onSupportNavigateUp()
}
In this navigation graph I take care of splash screen, login, register fragment and going to main fragment which has a BottomNavigationView with two sub fragments.
I made a menu for bottomNavView fragments and made a graph for them, menu id's match with bottom nav graph id's.
My layout looks like this:
<androidx.fragment.app.FragmentContainerView
android:id="#+id/nav_host_fragment_main"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="#+id/bottom_Navigation_view"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="#navigation/bottom_view_nav_graph" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/bottom_Navigation_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/white"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:menu="#menu/bottom_nav_menu" />
</androidx.constraintlayout.widget.ConstraintLayout>
In main fragment I am trying to set up bottom nav view with navigation graph like this:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val appCompat = requireActivity() as AppCompatActivity
val navHostFragment = appCompat.supportFragmentManager.findFragmentById(R.id.nav_host_fragment_main) as NavHostFragment
val navController = navHostFragment.findNavController()
binding.bottomNavigationView.setupWithNavController(navController)
}
However I keep getting this exception:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.ak.chatter, PID: 1937
java.lang.NullPointerException: null cannot be cast to non-null type androidx.navigation.fragment.NavHostFragment
at com.ak.chatter.ui.main.MainFragment.onViewCreated(MainFragment.kt:34)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:332)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java:413)
at android.os.Handler.handleCallback(Handler.java:900)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8347)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)
java.lang.NullPointerException: null cannot be cast to non-null type
androidx.navigation.fragment.NavHostFragment
You try to cast a null to a non-null.
The null is got from appCompat.supportFragmentManager.findFragmentById(R.id.nav_host_fragment_main) statement.
Because the supportFragmentManager is used as the fragment manager of fragments that are hosted by a fragment. Although the supportFragmentManager should manage fragments that are hosted by an activity.
Whereas the childFragmentManager should be used instead to manage fragments that are hosted by another fragment.
So, to solve this replace supportFragmentManager with childFragmentManager in the main fragment class:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val appCompat = requireActivity() as AppCompatActivity
val navHostFragment = appCompat.childFragmentManager.findFragmentById(R.id.nav_host_fragment_main) as NavHostFragment
val navController = navHostFragment.findNavController()
binding.bottomNavigationView.setupWithNavController(navController)
}
I am using Navigation Component for navigating in my app. It works fine inside fragments but it fails to find the nav host in the activity that holds the actual navigation host.
I am trying to open a new fragment when the user clicks on FAB, which I included in Main activity's XML. When I call findNavController() it fails to find the controller. The nav host controller is in the XML layout. I can't understand why it fails to find it.
MainActivity
class MainActivity : AppCompatActivity(), OnActivityComponentRequest {
override fun getTabLayout(): TabLayout {
return this.tabLayout
}
override fun getFap(): FloatingActionButton {
return this.floatingActionButton
}
private lateinit var tabLayout: TabLayout
private lateinit var floatingActionButton: FloatingActionButton
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
fab.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
}
Activity main XML
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
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"
tools:context=".domain.MainActivity"
android:animateLayoutChanges="true">
<com.google.android.material.appbar.AppBarLayout
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:theme="#style/AppTheme.AppBarOverlay">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/AppTheme.PopupOverlay"/>
<com.google.android.material.tabs.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.tabs.TabItem
android:text="Test 1"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
<com.google.android.material.tabs.TabItem
android:text="Test 2"
android:layout_height="match_parent"
android:layout_width="match_parent"/>
</com.google.android.material.tabs.TabLayout>
</com.google.android.material.appbar.AppBarLayout>
<fragment
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/main_navigation" />
<com.google.android.material.bottomappbar.BottomAppBar
android:id="#+id/bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/fab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_anchorGravity="right|top"
app:layout_anchor="#+id/bar"
android:src="#drawable/ic_add_black_24dp"/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
I was getting the same exeception until I managed to get the navController this way:
val navHostFragment = supportFragmentManager.findFragmentById(R.id.my_fragment_container_view_id) as NavHostFragment
val navController = navHostFragment.navController
Obtained from this answer:
Before finding the nav controller, you need to set the view, if you are using binding:
binding = BaseLayoutBinding.inflate(layoutInflater)
val view = binding.root
setContentView(view)
If not:
setContentView(R.layout.activity_main)
Use the corresponding binding for fragments.
Try setting up onClickListener of Fab button in onStart of the Activity as in onCreate Activity is just inflating the View and haven't set the NavHostController. So if you setup onClickListener in onStart of activity is will work as expected.
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(toolbar)
this.tabLayout = tabs
this.floatingActionButton = fab
}
override fun onStart() {
super.onStart()
floatingActionButton.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
}
In Java you can find NavController inside activity this way:
Navigation.findNavController(this,R.id.nav_host).navigate(R.id.YourFragment);
The problem might be that FAB was added to the activity or a fragment different from the one used by NavHost fragment. In this case, when you call it.findNavController() it cannot find the navigation controller.
You can either check that your FAB belongs to the fragment pulled by NavHost or call an Activity's findNavController(<id>) and pass it id of the fragment you're looking up
override fun onCreate(savedInstanceState: Bundle?) {
...
fab.setOnClickListener {
findNavController(R.id.nav_host_fragment)
.navigate(R.id.addNewWorkoutFragment)
}
}
Retrieve it later, in onPostCreate. like this:
#Override
public void onPostCreate(Bundle savedInstanceState ) {
super.onPostCreate(savedInstanceState);
navController = Navigation.findNavController(this, R.id.fragment_container_view);
}
Turns out that activity that holds navigation controller... doesn't have navigation component.
The solution is to manually set the NavController to each view contained in the activity.
val navController = findNavController(R.id.nav_host_fragment)
Navigation.setViewNavController(fab, navController)
Now this would work:
fab.setOnClickListener {
it.findNavController().navigate(R.id.addNewWorkoutFragment)
}
I still don't understand why this works the way it works so any explanation would be more than welcome :)
As of now, Android API simply doesn't make much sense.
Source: Navigate to fragment on FAB click (Navigation Architecture Components)
Kotlin Only
Android Navigation KTX provides an extension function for Activity
All I had to do was
findNavController(R.id.myNavHostFragment).navigate(R.id.to_someFragment)
I do have the following dependencies in my app/gradle.build.kts file (
implementation ("androidx.navigation:navigation-fragment-ktx:2.3.5")
implementation ("androidx.navigation:navigation-runtime-ktx:2.3.5")
implementation ("androidx.navigation:navigation-ui-ktx:2.3.5")
Using Directions
Alternatively you could also use generated Directions class. Since this is a global action the Directions class is found in the NavigationDirections.to_someFragment()
//very useful if you're passing args then you could do something like
//NavigationDirections.to_someFragment(myArg)
NavigationDirections.to_someFragment()findNavController(R.id.myNavHostFragment).navigate(NavigationDirections.to_someFragment())
Side-note the specific extension function is being contributed from the runtime-ktx aar
you can still get access in your oncreate by doing
//the id would be the id of the Fragment Element In Your Activity XML File
val navGraph = Navigation.findNavController(this, R.id.activity_main)
binding.mainFab.setOnClickListener {
navGraph.navigate(R.id.destinationFragment)
}
I found this answer helpful. In your activity paste this code
Navigation.findNavController(this, R.id.nav_host_fragment).navigate(R.id.yourDestination)
This is Extension version for Kotlin:
fun AppCompatActivity.findNavController(
#IdRes navHostViewId: Int
): NavController {
val navHostFragment =
supportFragmentManager.findFragmentById(navHostViewId) as NavHostFragment
return navHostFragment.navController
}
The navHostViewId is id of your androidx.fragment.app.FragmentContainerView.
The best way to access navController in OnCreate of Activity is to access it after inflating the layout
that can achieved by kotlin extention function doOnPreDraw()
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private val navController: NavController
get() = Navigation.findNavController(this, R.id.nav_host_fragment)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.root.doOnPreDraw {
// here you can safely use navController
binding.toolbar.setupWithNavController(navController)
}
}
}
You can use binding.root.findNavController().navigate(id)