条件成立时如何在片段中实现特定的后退按钮功能，否则使用默认的后退按钮功能？

Question

I want to clear selection on back button pressed on selection tracker when there are selected items and use default back button functionallity if there are no selected items.

I use Navigation Components for working with fragments.

Code in my fragment which implements OnBackPressedListener interface:

override fun onBackPressed() {
    if (tracker?.hasSelection() == true) tracker?.clearSelection()
    else findNavController().popBackStack()
}

Clear selection condition is working, but else block does not.

Code from my BaseActivity which determines how to use back button.

override fun onBackPressed() {
    val currentFragment = navHost.childFragmentManager.fragments[0]
    if (currentFragment is OnBackPressedListener) {
        currentFragment.onBackPressed()
    } else {
        super.onBackPressed()
    }
}

So, question is how to exit fragment (or pop backstack) when there are no selected items in selection tracker? It is working when I call

requireActivity().finish() 

, but I do not know if this is correct solution.

Answer 1

For this case, you could try registering OnBackPressedCallback on your Fragments via addOnBackPressedCallback. For more detail follow the below-given link:

https://developer.android.com/guide/navigation/navigation-custom-back