Android 如何从片段管理底部导航？

我试图将navController设置为bottomNavigation，但它需要活动，问题是我的borromNavigation托管在片段中，所以我没有活动实例

我试过了

bottom_nav_view.setupWithNavController(findNavController())

以及：

home_fragment.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
        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"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        tools:context=".ui.fragments.home.HomeFragment">

    <fragment
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toTopOf="@id/bottom_nav_view"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:id="@+id/my_nav_host_fragment"
            android:name="androidx.navigation.fragment.NavHostFragment"
            app:navGraph="@navigation/main_navigation"
            app:defaultNavHost="true"
            />

    <com.google.android.material.bottomnavigation.BottomNavigationView
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:id="@+id/bottom_nav_view"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:menu="@menu/bottom_menu" />

</androidx.constraintlayout.widget.ConstraintLayout>

bottom_menu.xml：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
            android:icon="@drawable/ic_schedule"
            android:id="@+id/scheduleFragment"
            android:title="Schedule"/>

    <item
            android:icon="@drawable/ic_database"
            android:id="@+id/archiveFragment"
            android:title="Database"/>
    <item
            android:id="@+id/teachersFragment"
            android:icon="@drawable/ic_teachers"
            android:title="Teachers"/>

    <item
            android:id="@+id/settingsFragment"
            android:icon="@drawable/ic_settings_"
            android:title="Settings"/>

</menu>

main_navigation.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/main_navigation"
            app:startDestination="@id/scheduleFragment">
    <fragment
            android:id="@+id/scheduleFragment"
            android:name="andy.schedulekpi.ui.fragments.schedule.ScheduleFragment"
            android:label="schedule_fragment"
            tools:layout="@layout/schedule_fragment"/>
    <fragment
            android:id="@+id/archiveFragment"
            android:name="andy.schedulekpi.ui.fragments.archive.ArchiveFragment"
            android:label="archive_fragment"
            tools:layout="@layout/archive_fragment"/>
    <fragment
            android:id="@+id/teachersFragment"
            android:name="andy.schedulekpi.ui.fragments.teachers.TeachersFragment"
            android:label="teachers_fragment"
            tools:layout="@layout/teachers_fragment"/>
    <fragment
            android:id="@+id/settingsFragment"
            android:name="andy.schedulekpi.ui.fragments.settings.SettingsFragment"
            android:label="settings_fragment"
            tools:layout="@layout/settings_fragment"/>

</navigation>

---

我本想从fragment处理bottomNavigation，但现在我单击了菜单项，没有发生任何问题或错误。

在HomeFragment中，在BottomNavigationView上设置navController：

import androidx.navigation.findNavController

然后，当您想从底部导航视图获取导航控制器时：

bottom_nav_view.findNavController()

---

在HomeFragment中，在BottomNavigationView上设置navController：

import androidx.navigation.findNavController

然后，当您想从底部导航视图获取导航控制器时：

bottom_nav_view.findNavController()

如前所述，在onActivityCreated中的HomeFragment中，我只需要添加

bottom_nav_view.setupWithNavController(activity!!.findNavController(R.id.my_nav_host_fragment))

因此，现在在HomeFragment中，我有：

package andy.schedulekpi.ui.fragments.home

import androidx.lifecycle.ViewModelProviders
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.navigation.Navigation
import androidx.navigation.findNavController
import androidx.navigation.fragment.navArgs
import androidx.navigation.ui.setupWithNavController

import andy.schedulekpi.R
import kotlinx.android.synthetic.main.home_fragment.*

import kotlinx.android.synthetic.main.home_fragment.view.*

class HomeFragment : Fragment() {

    companion object {
        fun newInstance() = HomeFragment()
    }

    private lateinit var viewModel: HomeViewModel


    val safeArgs : HomeFragmentArgs by navArgs()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view =  inflater.inflate(R.layout.home_fragment, container, false)


        return view
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProviders.of(this).get(HomeViewModel::class.java)
        // TODO: Use the ViewModel
        //Navigation.setViewNavController(bottom_nav_view, activity!!.findNavController(R.id.my_nav_host_fragment))
        bottom_nav_view.setupWithNavController(activity!!.findNavController(R.id.my_nav_host_fragment))

        Toast.makeText(this.context, safeArgs.currentWeek.toString(), Toast.LENGTH_SHORT).show()
    }

}

多亏了

如前所述，在onActivityCreated中的HomeFragment中，我只需添加

bottom_nav_view.setupWithNavController(activity!!.findNavController(R.id.my_nav_host_fragment))

因此，现在在HomeFragment中，我有：

package andy.schedulekpi.ui.fragments.home

import androidx.lifecycle.ViewModelProviders
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.navigation.Navigation
import androidx.navigation.findNavController
import androidx.navigation.fragment.navArgs
import androidx.navigation.ui.setupWithNavController

import andy.schedulekpi.R
import kotlinx.android.synthetic.main.home_fragment.*

import kotlinx.android.synthetic.main.home_fragment.view.*

class HomeFragment : Fragment() {

    companion object {
        fun newInstance() = HomeFragment()
    }

    private lateinit var viewModel: HomeViewModel


    val safeArgs : HomeFragmentArgs by navArgs()

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val view =  inflater.inflate(R.layout.home_fragment, container, false)


        return view
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProviders.of(this).get(HomeViewModel::class.java)
        // TODO: Use the ViewModel
        //Navigation.setViewNavController(bottom_nav_view, activity!!.findNavController(R.id.my_nav_host_fragment))
        bottom_nav_view.setupWithNavController(activity!!.findNavController(R.id.my_nav_host_fragment))

        Toast.makeText(this.context, safeArgs.currentWeek.toString(), Toast.LENGTH_SHORT).show()
    }

}

---

多亏了

请注意，如果您的导航主机是FragmentContainerView，则此解决方案不起作用！这个解决方案有效。我在导航主机FragmentContainerView上以这种方式使用它。请注意，如果您的导航主机是FragmentContainerView，则此解决方案不起作用！这个解决方案有效。我在导航主机FragmentContainerView上以这种方式使用它。请注意，如果您的导航主机是FragmentContainerView，则此解决方案不起作用！请注意，如果您的导航主机是FragmentContainerView，则此解决方案不起作用！