implement back button navigation and toolbar labeling

app/src/main/java/com/hako/friendlists/view/MainActivity.kt

@@ -3,6 +3,7 @@ package com.hako.friendlists.view
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
 import androidx.navigation.findNavController
+import androidx.navigation.ui.NavigationUI.setupActionBarWithNavController
 import com.hako.base.extensions.observeNonNull
 import com.hako.base.navigation.NavigationRouter
 import com.hako.friendlists.BuildConfig
@@ -36,10 +37,17 @@ class MainActivity : AppCompatActivity() {
             // Pair.second is a Bundle
             navController.navigate(pair.first, pair.second)
         }
+
+        setupActionBarWithNavController(this, navController)
     }
 
     private fun setupPicasso() {
         // Show cache indicator on images just for debug builds
         picasso.setIndicatorsEnabled(BuildConfig.DEBUG)
     }
+
+    override fun onSupportNavigateUp(): Boolean {
+        navController.navigateUp()
+        return super.onSupportNavigateUp()
+    }
 }

app/src/main/java/com/hako/friendlists/viewmodel/NavigationViewmodel.kt

@@ -12,6 +12,9 @@ import com.hako.friendlists.R
 import com.hako.photolist.feature.PHOTOLIST_FRAGMENT_BUNDLE_ALBUM_ID
 import com.hako.userlist.navigation.UserlistNavigation
 
+// This sets the fragment title, it's referenced in every navigation
+const val FRAGMENT_TITLE = "actionTitle"
+
 class NavigationViewmodel : ViewModel() {
 
     val navigate = MutableLiveData<Pair<@IdRes Int, Bundle>>()
@@ -29,6 +32,7 @@ class NavigationViewmodel : ViewModel() {
             is UserlistNavigation.ClickedOnUser -> navigate.postValue(
                 buildNavigation(R.id.action_userlistFragment_to_albumlistFragment, Bundle().apply {
                     putInt(ALBUMLIST_FRAGMENT_BUNDLE_USER_ID, event.userId)
+                    putString(FRAGMENT_TITLE, event.userName)
                 })
             )
         }