Is it possible to pass and access arguments in a fragment using a bottom navigation view and the Navigation component?
I'm using a one activity with many fragments approach where my top level fragment requires an argument(Usually done via the newInstance generated method). I've had a look at the Navigation component developer guide and the codelab but it only mentions using safeargs and adding argument tags in the destinations and actions.
Here's my navigation graph:
<navigation xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
app:startDestination="@id/homeFragment">
<fragment android:id="@+id/homeFragment"
android:name="uk.co.homeready.homeready.HomeFragment"
android:label="fragment_home"
tools:layout="@layout/fragment_home">
<!--Do I create an argument block here?-->
</fragment>
<fragment android:id="@+id/calculatorFragment"
android:name="uk.co.homeready.homeready.CalculatorFragment"
android:label="fragment_calculator"
tools:layout="@layout/fragment_calculator"/>
<fragment android:id="@+id/resourcesFragment"
android:name="uk.co.homeready.homeready.ResourcesFragment"
android:label="fragment_resources"
tools:layout="@layout/fragment_resources"/>
</navigation>
Bottom Navigation View menu:
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:id="@+id/homeFragment"
android:icon="@drawable/ic_home_black_24dp"
android:title="@string/title_home"/>
<item
android:id="@+id/calculatorFragment"
android:icon="@drawable/ic_baseline_attach_money_24px"
android:title="@string/title_calculator"/>
<item
android:id="@+id/resourcesFragment"
android:icon="@drawable/ic_baseline_library_books_24px"
android:title="@string/title_resources"/>
</menu>
MainActivity:
override fun onCreate(savedInstanceState: Bundle?) {
...
val navController = Navigation.findNavController(this,
R.id.nav_host_fragment)
bottom_navigation.setupWithNavController(navController)
....
}
activity_main.xml
<android.support.constraint.ConstraintLayout>
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
app:layout_constraintBottom_toTopOf="@id/bottom_navigation"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph"/>
<android.support.design.widget.BottomNavigationView
android:id="@+id/bottom_navigation"
app:menu="@menu/bottom_navigation"/>
</android.support.constraint.ConstraintLayout>
HomeFragment
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val argument = //TODO access argument here
...
}
If I understood you correctly, you want to pass arguments to destinations that is tied to menu items. Try to use 'OnDestinationChangedListener' inside your activity onCreate method, something like this:
navController.addOnDestinationChangedListener { controller, destination, arguments ->
when(destination.id) {
R.id.homeFragment -> {
val argument = NavArgument.Builder().setDefaultValue(6).build()
destination.addArgument("Argument", argument)
}
}
}
Update:
If you want that your start destination will receive default arguments the implementation should be different. First, remove 'app:navGraph="@navigation/nav_graph"' from your 'NavHostFragment' xml tag.
Then, inside your activity onCreate you need to inflate the graph:
val navInflater = navController.navInflater
val graph = navInflater.inflate(R.navigation.nav_graph)
Then add your arguments to graph(this arguments will be attached to start destination)
val navArgument1=NavArgument.Builder().setDefaultValue(1).build()
val navArgument2=NavArgument.Builder().setDefaultValue("Hello").build()
graph.addArgument("Key1",navArgument1)
graph.addArgument("Key2",navArgument2)
Then attach the graph to NavController:
navController.graph=graph
Now your first destination should receive the attached arguments.
The correct way to do this is indeed with an <argument>
block on your destination.
<fragment android:id="@+id/homeFragment"
android:name="uk.co.homeready.homeready.HomeFragment"
android:label="fragment_home"
tools:layout="@layout/fragment_home">
<argument
android:name="Argument"
android:defaultValue="value"
/>
</fragment>
This will automatically populate the arguments of the Fragment with the default value without any additional code needed. As of Navigation 1.0.0-alpha09, this is true whether you use the Safe Args Gradle Plugin or not.
Default values was not usable for me, because I have dynamic menu items that could have multiple of the same destination with different arguments. (changed from server)
Implement BottomNavigationView.OnNavigationItemSelectedListener:
override fun onNavigationItemSelected(item: MenuItem): Boolean {
val fragmentId = item.itemId
val arguments = argumentsByFragmentId[fragmentId] // custom mutableMapOf<Int, Bundle?>() with arguments
navController().navigate(fragmentId, arguments)
return true
}
To use that you will takeover the navigation, by replacing the listener. The order of calls here are important:
bottomNavigationView.setupWithNavController(navController)
bottomNavigationView.setOnNavigationItemSelectedListener(this)
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