Custom “navigate up” behavior for certain fragment using Navigation component

Question

I want to add custom up navigation from fragment using Navigation component

In my build.gradle(app) I use androidx.appcompat:appcompat:1.1.0-

Answer 1

You need to call onBackPressed() from onBackPressedDispatcher property. Assuming your Toolbar is properly setup you can use the code below in your Activity.

override fun onOptionsItemSelected(menuItem : MenuItem?) : Boolean {
    if (menuItem.getItemId() == android.R.id.home) {
        onBackPressedDispatcher.onBackPressed()
        return true // must return true to consume it here

    }
    return super.onOptionsItemSelected(menuItem)
}

on Fragment override

override fun onAttach(context: Context) {
        super.onAttach(context)            

        //enable menu
        setHasOptionsMenu(true)

        requireActivity()
                .onBackPressedDispatcher
                .addCallback(this){
                   //true means that the callback is enabled
                    this.isEnabled = true
                    exitDialog() //dialog to conform exit
                }
    }

What this does is :

Trigger a call to the currently added OnBackPressedCallback callbacks in reverse order in which they were added. Only if the most false from its OnBackPressedCallback#handleOnBackPressed() will any previously added callback be called.

I am using AndroidX in my example therefore my import will look like

import androidx.appcompat.app.AppCompatActivity.