I'm building an android application with 3 menus using bottom navigation. I created new project in Android Studio using Bottom Navigation Activity.
I renamed the fragment to:
InfoFragment.kt
DetectFragment.kt
AboutFragment.kt
Renamed the layout in src/main/res/layout to:
fragment_info.xml
fragment_detect.xml
fragment_about.xml
Renamed the menu in src/main/res/menu to:
navigation_info
navigation_detect
navigation_about
In the fragment_about.xml I added a Button buttonGoToFAQ to navigate to fragment_faq like this with this code in AboutFragment.kt
buttonGoToFAQ.setOnClickListener {
val action = AboutFragmentDirections.actionFAQ()
Navigation.findNavController(it).navigate(action)
}
After I clicked BottomNavigationView menu either navigation_info or navigation_detect, and go back by clicking navigation_about menu, the selected menu on the BottomNavigationView is not changed.
See this picture.
What I want is the menu navigation_about should have been selected instead of other menu.
I already tried overriding fun onStart() and fun onResume() in FAQFragment.kt but to no avail.
nav_view is my BottomNavigationView.
override fun onStart() {
super.onStart()
(requireActivity().findViewById<View>(R.id.nav_view) as BottomNavigationView).selectedItemId =
R.id.navigation_about
}
I also recognize that all the BottomNavigationView menu's id have the same ids as the id in the src/main/res/navigation xml file
After some days, I finally get the answer by myself. First, I need to get the BottomNavigationView from MainActivity, after that, you can just change the menu item value from another fragment.
In MainActivity.kt:
companion object {
lateinit var binding: ActivityMainBinding
{
On Fragment,
Define BottomNavigationView and set the desired index in onResume():
class FAQFragment : Fragment() {
private val navView: BottomNavigationView = MainActivity.binding.navView
...
override fun onResume() {
super.onResume()
navView.menu.getItem(2).isChecked = true
}
}