Utlity classes to enable the handling of backpressed in Fragments

FragmentNavigationManager.kt

interface FragmentNavigationManager {

    fun onNavigateUp(): Boolean

    fun registerUpNavigationListener(upNavigationListener: UpNavigationListener)

    fun unregisterUpNavigationListener(upNavigationListener: UpNavigationListener)

}

FragmentNavigationManagerImpl.kt

import android.support.v7.app.AppCompatActivity
import eu.widgetlabs.fleet.core.utility.Collections
import java.util.*

class FragmentNavigationManagerImpl(private val appCompatActivity: AppCompatActivity) : FragmentNavigationManager {

    private val listenerStack: MutableList<UpNavigationListener> = ArrayList<UpNavigationListener>(10)

    override fun onNavigateUp(): Boolean {
        val listener = Collections.lastObject(listenerStack) ?: return false
        return listener.onNavigateUp(appCompatActivity.supportFragmentManager, this)
    }

    override fun registerUpNavigationListener(upNavigationListener: UpNavigationListener) {
        listenerStack.add(upNavigationListener)
    }

    override fun unregisterUpNavigationListener(upNavigationListener: UpNavigationListener) {
        listenerStack.remove(upNavigationListener)
    }
}

UpNavigationListener.kt

import android.support.v4.app.FragmentManager

interface UpNavigationListener {

    fun onNavigateUp(fragmentManager: FragmentManager, fragmentNavigationManager: FragmentNavigationManager): Boolean

}