Not navigating back to previous fragment with DrawerLayout and BottomNavigationView-CodePudding

The

MainActivity

public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mBinding = ActivityMainBinding.inflate(getLayoutInflater()); setContentView(mBinding.getRoot()); setSupportActionBar(mBinding.appBarMain.mainToolbar); mBottomNav = mBinding.appBarMain.mainBottomBar; mDrawerLayout = mBinding.drawerLayout; NavigationView navigationView = mBinding.navView; mAppBarConfiguration = new AppBarConfiguration.Builder( R.id.home, R.id.readings, R.id.graph) .setOpenableLayout(mDrawerLayout) .build(); NavController navController = Navigation.findNavController(this, R.id.main_fragments_container); NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration); NavigationUI.setupWithNavController(navigationView, navController); NavigationUI.setupWithNavController(mBottomNav, navController); } @Override public boolean onOptionsItemSelected(MenuItem item) { NavController navController = Navigation.findNavController(this, R.id.main_fragments_container); return NavigationUI.onNavDestinationSelected(item, navController) || super.onOptionsItemSelected(item); } @Override public boolean onSupportNavigateUp() { NavController navController = Navigation.findNavController(this, R.id.main_fragments_container); return NavigationUI.navigateUp(navController, mAppBarConfiguration) || super.onSupportNavigateUp(); } }

nav_graph.xml

<?xml version="1.0" encoding="utf-8"?> <navigation xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:id="@ id/nav_graph" app:startDestination="@ id/home"> <fragment android:id="@ id/home" android:name="com.myapp.ui.tabs.HomeFragment" android:label="@string/menu_title_home" tools:layout="@layout/fragment_home" /> <fragment android:id="@ id/readings" android:name="com.myapp.ui.tabs.ReadingsFragment" android:label="@string/menu_title_readings" tools:layout="@layout/fragment_readings" /> <fragment android:id="@ id/graph" android:name="com.myapp.ui.tabs.GraphFragment" android:label="@string/menu_title_graph" tools:layout="@layout/fragment_graph" /> <fragment android:id="@ id/about" android:name="com.myapp.ui.about.AboutFragment" android:label="@string/general_about" tools:layout="@layout/fragment_about" /> </navigation>

NOTE As a test, if I make the FAB button (visible on all BottomNavigation fragment screens) go to AboutFragment, then when I click 'up' arrow in the AboutFragment it DOES take me back to Readings. It seems that accessing AboutFragment via the DrawerLayout acts differently to accessing AboutFragment from the FAB.

CodePudding user response：

Can you try to:

override fun onSupportNavigateUp(): Boolean { val navController = this.findNavController(R.id.mainNavHostFragment) return when(navController.currentDestination?.id) { R.id.about-> { popBackStack() true } else -> navController.navigateUp() } }

Let me know if it works for you

CodePudding user response：

Answering my own question here for anyone else who has this problem. Solution is to put android:menuCategory="secondary" in the AboutFragment item in the DrawerLayout menu file.

menu_drawer.xml

<item android:id="@ id/nav_about" android:menuCategory="secondary" android:icon="@drawable/vic_about" android:title="@string/general_about" />

Reason this works is:

By default, the back stack will be popped back to the navigation graph's start destination. Menu items that have android:menuCategory="secondary" will not pop the back stack.

I found the solution in this post https://stackoverflow.com/a/60516769/728002