为什么我的Fragment中的TabLayout只能在第一次使用？

Question

我在片段上使用TabLayout时遇到问题。它只是通过显示另一个片段来执行，但是在我单击其他应用程序部分然后返回到包含TabLayout的片段之后，则不显示TabLayout内容。

My TabLayout Problem Ilustrate

class favoriteFragment：Fragment（）{

    private var tabLayout: TabLayout? = null
    private var viewPager: ViewPager? = null

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment_favorites, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        tabLayout = view.findViewById(R.id.tabs) as TabLayout
        viewPager = view.findViewById(R.id.viewpager) as ViewPager
        super.onViewCreated(view, savedInstanceState)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        viewPager!!.setAdapter(MyAdapter(fragmentManager))
        tabLayout!!.post(Runnable { tabLayout!!.setupWithViewPager(viewPager) })
        super.onActivityCreated(savedInstanceState)
    }

    private inner class MyAdapter(fm: FragmentManager?) : FragmentPagerAdapter(fm!!, FragmentPagerAdapter.BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
        private val int_items = 2

        override fun getItem(position: Int): Fragment {
            var fragment: Fragment? = null
            when (position) {
                0 -> fragment = MoviesFavoritesFragment()
                1 -> fragment = TvSeriesFavoritesFragment()
            }
            return fragment!!
        }

        override fun getCount(): Int {
            return int_items
        }

        override fun getPageTitle(position: Int): CharSequence? {
            when (position) {
                0 -> return "Movie Favorites"
                1 -> return "Tv Series  Favorites"
            }
            return null
        }
    }
} 

这里是我的XML

   <?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:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/material_blue_grey_800"
        app:tabGravity="fill"
        app:tabIndicatorColor="@color/colorPrimary"
        app:tabSelectedTextColor="@color/white"
        app:tabTextColor="@color/colorPrimary"
        app:layout_constraintTop_toTopOf="parent"/>

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toBottomOf="@id/tabs"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

最有可能的错误是在这里：

viewPager!!.setAdapter(MyAdapter(fragmentManager))

尝试在此处传递childFragmentManager