我有两个片段，我想要创建他们之间的互动使用向后按钮在动作栏。 理想情况下，我希望保存上一个片段的状态。 我只能找到活动的信息。

我找到了这个碎片

private fun setupBackButton() {
        if (activity is AppCompatActivity) {
            (activity as AppCompatActivity?)?.supportActionBar?.setDisplayHomeAsUpEnabled(true)
        }
    }

但它只显示后退按钮，点击后不会发生任何事情。

编辑

在第一个片段中，我将第二个片段称为:

val fragment = UserContentFragment()
fragment.setUser(item.user)

if (fragmentManager != null) {
    fragmentManager!!
      .beginTransaction()
      .replace(R.id.main_layout, fragment)
      .addToBackStack(null)
      .commit()
}

这是我的UserContentFragment第二个片段:

class UserContentFragment : Fragment() {

    private lateinit var user: SearchUser

    fun setUser(user: SearchUser) {
        this.user = user
    }

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

        val userImage = root.findViewById(R.id.user_img) as ImageView
        if (context != null) {
            Glide.with(context!!)
                .load(user.profile_pic_url)
                .circleCrop()
                .into(userImage)
        }

        val userName: TextView = root.findViewById(R.id.user_name)
        userName.text = user.full_name

        val toolbar: Toolbar = root.findViewById(R.id.toolbar)
        toolbar.setNavigationOnClickListener { requireActivity().onBackPressed() }

        setupBackButton()
        
        return root
    }

    private fun setupBackButton() {
        if (activity is AppCompatActivity) {
            (activity as AppCompatActivity?)?.supportActionBar?.setDisplayHomeAsUpEnabled(true)
        }
    }
}

下面是its的。xml文件:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:background="@color/colorBlack">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/user_title"
        android:layout_width="match_parent"
        android:layout_height="100dp">

        <ImageView
            android:id="@+id/user_img"
            android:layout_width="80dp"
            android:layout_height="80dp"
            android:layout_marginStart="16dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:ignore="ContentDescription" />

        <TextView
            android:id="@+id/user_name"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="32dp"
            android:layout_marginEnd="16dp"
            android:textColor="@color/colorWhite"
            android:textSize="22sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/user_img"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</RelativeLayout>