Bottom Navigation with Drawer Layout | onBackPressed in Fragment-CodePudding

I have an interesting and confusing question.

I have a Drawer Layout that opens from the Bottom Navigation like in the photo

Screens:

In order for Drawer Layout to open from the Bottom Navigation, I used this code:

    bottomNavigationView.setOnItemSelectedListener { item ->
            when (item.itemId) {
                R.id.itemDrawer -> {
                    drawerLayout.openDrawer(GravityCompat.END)
                    return@setOnItemSelectedListener false
                }
                R.id.homeFragment -> navController.navigate(R.id.homeFragment)
                R.id.booksFragment -> navController.navigate(R.id.booksFragment)
                R.id.grammarFragment -> navController.navigate(R.id.grammarFragment)
                R.id.translatorFragment -> navController.navigate(R.id.translatorFragment)
            }
            true
        }

This is what my problem is

When I override listener for Bottom Navigation, in my opinion, the onBackPressed behaviour gets confused default.

I mean that when I click on Home, then another element, then Home again, and so on several times, and I stay on the Home Fragment and click on onBackPressed, then instead of leaving the app, I go back to the fragment where I was before

I think this is not normal for the user

What should I do?

I thought to somehow override onBackPressed for Home Fragment but I don't understand how to do it

CodePudding user response：

You can use onBackPressedDispatcher in your HomeFragment

private lateinit var onBackPressedCallback: OnBackPressedCallback

and instantiate the implementation and add the callback to activity in onResume()

override fun onResume() {
    super.onResume()
    onBackPressedCallback = object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                activity?.moveTaskToBack(true)
                exitProcess(ZERO)
            }
        }
    
    activity?.onBackPressedDispatcher?.addCallback(onBackPressedCallback)
}

Due to this callback added on activity, then the callback should be removed on leaving HomeFragment

override fun onPause() {
    onBackPressedCallback.remove()
    super.onPause()
}

CodePudding user response：

I found the answer.

Everything is as in the selected answer, but need to remove this callback in the onPause of this fragment. To prevent the app from closing from all fragments

1. Create a variable for callback

private lateinit var mCallback: OnBackPressedCallback

2. In onViewCreated :

mCallback = object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                activity?.moveTaskToBack(true)
                exitProcess(0)
            }
        }

activity?.onBackPressedDispatcher?.addCallback(mCallback)

3. Remove callback when closing the fragment

 override fun onPause() {
        mCallback.remove()
        super.onPause()
    }