I try to write an Android app which uses the Navigation Component from androidx, a toolbar and a drawer layout to slide in a setting menu from the left. I followed the guides Get started with the Navigation component and tried to add a top app bar and a setting using this guide Update UI components with NavigationUI.
When my apps starts, the following exception is thrown:
java.lang.IllegalStateException: Activity ....MainActivity@e686cd8 does not have a NavController set on 2131230993
Side remark: If I open nav_graph.xml
in design mode, the hosts pane reports "No NavHostFragments found. This nav graph must be referenced from a NavHostFragment in a layout in order to be accessible." Maybe this error and the exception are related and share the same root cause. However, my navigation graph is referenced by a NavHostFragment
though, see below.
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.drawerlayout.widget.DrawerLayout 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/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="@+id/main_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
android:theme="?attr/actionBarTheme" />
<androidx.fragment.app.FragmentContainerView
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
</LinearLayout>
<com.google.android.material.navigation.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:fitsSystemWindows="true"
app:menu="@menu/drawer_view"
app:headerLayout="@layout/nav_header" />
</androidx.drawerlayout.widget.DrawerLayout>
This layout
- contains a
FragmentContainerView
- references
@navigation/nav_graph
(pasted below) - contains a
NavigationView
- references
@layout/nav_header
(pasted below) - references
@menu/drawer_view
(pasted below)
nav_header.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.widget.LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="192dp"
android:background="?attr/colorPrimaryDark"
android:gravity="bottom"
android:padding="16dp"
android:theme="@style/ThemeOverlay.AppCompat.Dark">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/app_name"
android:textAppearance="@style/TextAppearance.AppCompat.Body1" />
</android.widget.LinearLayout>
drawer_view.xml:
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<group android:checkableBehavior="single">
<item
android:id="@+id/nav_home"
android:icon="@drawable/ic_home"
android:title="@string/home"/>
<item
android:id="@+id/nav_settings"
android:icon="@drawable/ic_settings"
android:title="@string/settings" />
</group>
</menu>
fragment_home.xml:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".HomeFragment"/>
This fragment is referenced by nav_graph
(pasted below) as the home fragment (start destination).
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/homeFragment">
<fragment
android:id="@+id/homeFragment"
android:name="de.mhnnet.lychee4android.HomeFragment"
android:label="fragment_home"
tools:layout="@layout/fragment_home" />
</navigation>
MainActivity.java:
protected void onCreate( Bundle savedInstanceState ) {
super.onCreate( savedInstanceState );
setContentView( R.layout.activity_main );
NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment );
AppBarConfiguration appBarConfiguration =
new AppBarConfiguration.Builder(navController.getGraph()).build();
Toolbar toolbar = findViewById( R.id.main_toolbar );
NavigationUI.setupWithNavController( toolbar, navController, appBarConfiguration );
}
Further Remarks:
I already found some tips which says that androidx.fragment.app.FragmentContainerView
should be replaced by fragment
. However, this feels wrong as the linter recommends to use FragmentContainerView
instead of fragment
and the official Android docs use FragmentContainerView
, too.
findFragmentById()
must be used, becausefindNavController
does not work inonCreate()
. But the latter is what the Google Android Docs recommend. – Bumboat