implementation 'com.google.android.material:material:1.0.0'

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout

        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/container"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        tools:context=".MainActivity">

    <androidx.viewpager.widget.ViewPager

            android:id="@+id/viewpager"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            app:layout_constraintEnd_toEndOf="parent"

            app:layout_constraintStart_toStartOf="parent"

            app:layout_constraintTop_toTopOf="parent"

            app:layout_constraintBottom_toTopOf="@id/nav_view"/>

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

            android:id="@+id/nav_view"

            android:layout_width="0dp"

            android:layout_height="wrap_content"

            android:layout_marginEnd="0dp"

            android:layout_marginStart="0dp"

            android:background="?android:attr/windowBackground"

            app:layout_constraintBottom_toBottomOf="parent"

            app:layout_constraintLeft_toLeftOf="parent"

            app:layout_constraintRight_toRightOf="parent"

            app:menu="@menu/bottom_nav_menu"/>

</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>

<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item

            android:id="@+id/navigation_home"

            android:icon="@drawable/ic_home_black_24dp"

            android:title="@string/title_home"/>

    <item

            android:id="@+id/navigation_dashboard"

            android:icon="@drawable/ic_dashboard_black_24dp"

            android:title="@string/title_dashboard"/>

    <item

            android:id="@+id/navigation_notifications"

            android:icon="@drawable/ic_notifications_black_24dp"

            android:title="@string/title_notifications"/>

</menu>

import androidx.fragment.app.Fragment

import androidx.fragment.app.FragmentManager

import androidx.fragment.app.FragmentPagerAdapter

class MyPagerAdapter(fm: FragmentManager,val fts:List<Fragment>) : FragmentPagerAdapter(fm) {

    override fun getItem(position: Int): Fragment {

        return fts[position]

    }

    override fun getCount(): Int {

        return fts.size

    }

}

class HomeFragment : Fragment() {

    private var param: String? = null

    private lateinit var baseView:View

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        arguments?.let {

            param = it.getString("param")

        }

    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,

                              savedInstanceState: Bundle?): View? {

        baseView = inflater.inflate(R.layout.fragment_home, container, false)

        baseView.text.text = param

        return baseView

    }

}

class MainActivity : AppCompatActivity() {

    private val onNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener {

        when(it.itemId){

            R.id.navigation_home -> {

                viewpager.currentItem = 0

                return@OnNavigationItemSelectedListener true

            }

            R.id.navigation_dashboard -> {

                viewpager.currentItem = 1

                return@OnNavigationItemSelectedListener true

            }

            R.id.navigation_notifications -> {

                viewpager.currentItem = 2

                return@OnNavigationItemSelectedListener true

            }

        }

        false

    }

    private val onPageChangeListener = object : ViewPager.OnPageChangeListener {

        override fun onPageScrollStateChanged(state: Int) {

        }

        override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {

        }

        override fun onPageSelected(position: Int) {

            when(position){

                0 -> {nav_view.selectedItemId = R.id.navigation_home}

                1 -> {nav_view.selectedItemId = R.id.navigation_dashboard}

                2 -> {nav_view.selectedItemId = R.id.navigation_notifications}

            }

        }

    }

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        nav_view.setOnNavigationItemSelectedListener(onNavigationItemSelectedListener)

        val f1 = HomeFragment()

        var args = Bundle()

        args.putString("param",getString(R.string.title_home))

        f1.arguments = args

        val f2 = HomeFragment()

        args = Bundle()

        args?.putString("param",getString(R.string.title_dashboard))

        f2.arguments = args

        val f3 = HomeFragment()

        args = Bundle()

        args?.putString("param",getString(R.string.title_notifications))

        f3.arguments = args

        val fts = listOf(f1, f2, f3)

        val fm = supportFragmentManager

        viewpager.adapter = MyPagerAdapter(fm,fts)

        viewpager.addOnPageChangeListener(onPageChangeListener)

    }

}

labeled     所有的标签都是可见的。

unlabeled  只显示图标。

selected    将只显示选定项和移位项的标签。

auto         将根据您拥有的项目数选择“标记”或“选定”。标记为1-3项，选择为3+项。