小编Аза*_*ков的帖子

我正在尝试使用带有底部导航视图的 androidx 导航。所以当我在 xml 文件中放置带有 android:name = "androidx.navigation.fragment.NavHostFragment" 的片段时，它给了我一个错误。我猜 xml 没有看到这个库或这个 Fragment

Here is xml file :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".weather.WeatherActivity"
        android:orientation="vertical"
        android:weightSum="10"
>
    <androidx.appcompat.widget.Toolbar
            android:id="@+id/w_toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay"
            android:theme="@style/ToolbarColoredBackArrow"
    />
        <fragment
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="9.6"
                android:id="@+id/nav_host_fragment"
                app:defaultNavHost = "true"
                app:navGraph = "@navigation/mobile_navigation"
                android:name="androidx.navigation.fragment.NavHostFragment"
                  />
        <com.google.android.material.bottomnavigation.BottomNavigationView
                android:id="@+id/bottom_nav"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="0.4"
                app:menu="@menu/bottom_nav"
        >

        </com.google.android.material.bottomnavigation.BottomNavigationView>

</LinearLayout>


Activity class:
class WeatherActivity : AppCompatActivity() {
    private lateinit var navController: NavController
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(com.example.upgrade.R.layout.activity_weather)
        val …