Android Jetpack Navigation How to handle the Toolbar and BottomNavBar content

问题

I am a bit confused on how the Navigation component fits in the app behavior. It all looks nice and shiny in tutorials where you don't do things too complex but when implementing in real app, things seem different.

Before Navigation

Before implementing navigation I had to manually run fragment transactions. In order to do this, my fragment would implement an interface onFragmentAction which passed a bundle to the main Activity and in the activity based on the actions, replace the current fragment with another one.

The second part that needs handling is the top toolbar and the BottomAppBar. For instance BottomAppBar needs to have the FAB aligned differently on some fragments or hidden in others. Also the top ToolBar needs to be expanded on some or collapsed on others. To do this, I listened to FragmentManager.OnBackStackChangedListener and based on the fragment tag getSupportFragmentManager().getBackStackEntryAt(size - 1).getName() change the layout accordingly.

With Navigation

The first part seems to be easy to do: pass params and start new fragments. But I have no idea if navigation can handle the toolbars management or I need to keep managing it from my Activity.

回答1:

The toolbar title is set based on 'label' value inside navigation graph, if you want to do something different with toolbar or BottomAppBar you can add addOnNavigatedListener inside your activity, and based on current destination do something.

findNavController(nav_host_fragment).addOnNavigatedListener { controller, 
 destination ->
 when(destination.id) {
    R.id.destination1 -> {
        //Do something with your toolbar or BottomAppBar
    }
    R.id.destination2 -> {
        //Do something with your toolbar or BottomAppBar
    }

 }
}

回答2:

Even though Alex's solution works, I would not recommend it for the purpose of managing the toolbar.

The toolbar should be part of your fragment's layout and each fragment should manage its own toolbar. you can inflate different menus for each fragment. even in the case of wanting to have the toolbar in the activity, I would recommend getting a reference to the toolbar form activity (through an interface) and then adding and manipulating its items in the fragment itself.

This would decouple your activity and fragment (which is one of the goals of having navigation graph and a router). a good rule of thumb is that imagine you want to remove the fragment, then you should not need to make any change to the activity.

回答3:

In your fragment:

NavController navHostFragment = NavHostFragment.findNavController(this);
NavigationUI.setupWithNavController(toolbar, navHostFragment);

When I click item on list item (Explore Fragment) it will negation to DetailFragment and when I click the back button on the toolbar it will return MainFragment.

回答4:

if you want to reach to another fragment by calling on menu item, you must give to item id the the same id which is in the destination id.

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return 
       item.onNavDestinationSelected(findNavController(R.id.nav_host_fragment))
            || super.onOptionsItemSelected(item)
}


<item android:id="@+id/dailyInfoFragment"
      android:title="@string/action_settings"
      android:orderInCategory="100"
      app:showAsAction="never"/>


    <fragment
        android:id="@+id/dailyInfoFragment"
        android:name="com.example.sonyadmin.infoPerDay.DailyInfoFragment"
        android:label="fragment_daily_info"
        tools:layout="@layout/fragment_daily_info"
        />

来源：https://stackoverflow.com/questions/51376447/android-jetpack-navigation-how-to-handle-the-toolbar-and-bottomnavbar-content