如何解决“没有NavController设置”。

Question

我想从主要碎片中获取细节片段。

错误 w/system.err：java.lang.illegalstateException：view androidx.cardview.widget.cardview {7fe29a5 vfe ... c .. ... c .. ...没有NavController集 w/system.err：at androidx.navigation.navigation.findnavcontroller（navigation.kt：71） w/system.err：在com.isilon.beinconnect.ui.main.Adapter.mainadapter.onbindviewholder $ lambda-0（mainadapter.kt：68） w/system.err：at com.isilon.beinconnect.ui.Main.Adapter.MainAdapter。$ R8 $ LAMBDA $ J_WJTHWACOLMQLIL361QLBA-I6M（未知来源：0） w/system.err：at com.isilon.beinconnect.ui.main.Adapter.MainAdapter $$ externalsyntheticlambda0.onclick（未知来源：6） 适配器

 override fun onBindViewHolder(holder: DataViewHolder, position:   Int) {
              holder.bind(data[position])
    
            holder.itemView.setOnClickListener{
    
                val resultData = data[position]
    
    
                val action =          MainFragmentDirections.actionMainFragmentToDetailFragment()
                action.releaseDate = resultData.release_date
                val navController = Navigation.findNavController(holder.itemView)
                navController.navigate(action)
            }
        }

xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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/scrollView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/navigation" />
</LinearLayout>

详细信息xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="horizontal"
    tools:context=".ui.main.view.DetailFragment">

    <ImageView
        android:id="@+id/iv_detail_avatar"
        android:layout_width="wrap_content"
        android:layout_height="150dp"
        android:layout_margin="15dp"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        <TextView
            android:id="@+id/tv_adult"
            android:layout_width="wrap_content"
            android:textSize="20sp"
            android:textColor="@android:color/background_dark"
            android:layout_height="wrap_content"
            android:layout_margin="15dp"/>

        <TextView
            android:id="@+id/tv_release_date"
            android:layout_width="wrap_content"
            android:textSize="20sp"
            android:textColor="@android:color/background_dark"
            android:layout_height="wrap_content"
            android:layout_margin="15dp"/>
    </LinearLayout>

</LinearLayout>

导航

<?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/navigation"
    app:startDestination="@id/mainFragment">

    <fragment
        android:id="@+id/mainFragment"
        android:name="com.isilon.beinconnect.ui.main.view.MainFragment"
        android:label="fragment_main"
        tools:layout="@layout/fragment_main" >
        <action
            android:id="@+id/action_mainFragment_to_detailFragment"
            app:destination="@id/detailFragment" />
    </fragment>
    <fragment
        android:id="@+id/detailFragment"
        android:name="com.isilon.beinconnect.ui.main.view.DetailFragment"
        android:label="fragment_detail"
        tools:layout="@layout/fragment_detail" >
        <argument
            android:name="releaseDate"
            app:argType="string"
            app:nullable="true"
            android:defaultValue="No Release Date" />
        <argument
            android:name="avatar"
            app:argType="string"
            app:nullable="true"
            android:defaultValue="No Avatar Img" />
        <argument
            android:name="adult"
            app:argType="boolean"
            android:defaultValue="false" />
    </fragment>
</navigation>

Answer 1

我会那样做

(itemView.context as AppCompatActivity).findNavController(R.id.fragmentContainerView).navigate(action)

Answer 2

FindNavController无法编程添加的视图，而不会像viweweholder一样附加到父母视图上
因此，您需要找到用于recyclerview的NAV控制器，而不是ViewHolder ItMeview

private var mRecyclerView : RecyclerView? = null
override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
    super.onAttachedToRecyclerView(recyclerView)
    mRecyclerView = recyclerView
}

override fun onDetachedFromRecyclerView(recyclerView: RecyclerView) {
    super.onDetachedFromRecyclerView(recyclerView)
    mRecyclerView = null// to avoid memory leak
}
override fun onBindViewHolder(holder: DataViewHolder, position:   Int) {
    holder.bind(data[position])
    holder.itemView.setOnClickListener{
        val resultData = data[position]
        val action =          MainFragmentDirections.actionMainFragmentToDetailFragment()
        action.releaseDate = resultData.release_date
        val navController = Navigation.findNavController(mRecyclerView!!)
        navController.navigate(action)
    }
}

Q：为什么FindNavController无法编程添加的视图？
答：因为nav控制器在创建弱参考自身时将标签添加到所有视图中，因此当您以编程方式添加视图且不附加到父级时，FindNavController将无法获得您的根视图，因此将无法找到它的参考较弱。