如何重新附加片段（片段未附加到 activity Kotlin）

Question

我对这个错误 Fragment not attached to an activity 感到很沮丧，我有一个片段开始一个 activity 并且 activity 开始另一个 activity 所以等等 F -> A1 -> A2 -> A3，在我完成最后一个 A3 之后，我打电话回到托管 activity

val intent = Intent(applicationContext, TabbarActivity::class.java)
        intent.putExtra("finish", "true")
        intent.flags = Intent.FLAG_ACTIVITY_CLEAR_TASK.or(Intent.FLAG_ACTIVITY_NEW_TASK)
        startActivity(intent)
        finish()

但是当我设置 Intent.FLAG_ACTIVITY_CLEAR_TASK 时，它从 activity 中分离了我的片段，然后我得到了这个错误 Fragment not attached to an activity，如果我重新运行我的应用程序，一切都会正常工作。

这里是主机Activity

private var bottomNavigation: BottomNavigationView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_tabbar)


        val finish = intent.getStringExtra("finish")

        bottomNavigation = findViewById(R.id.bottomNavigationView)
        val navigationController = findNavController(R.id.fragment)

        bottomNavigation?.setupWithNavController(navigationController)
        bottomNavigation?.itemIconTintList = null


        val firstFragment: Fragment = Fragment1()
        val secondFragment: Fragment = Fragment2()
        val thirdFragment: Fragment = Fragment3()
        val forthFragment: Fragment = Fragment4()
        var active = firstFragment


        supportFragmentManager.beginTransaction().add(R.id.containerb, forthFragment, "4").hide(forthFragment).commit()
        supportFragmentManager.beginTransaction().add(R.id.containerb, thirdFragment, "3").hide(thirdFragment).commit()
        supportFragmentManager.beginTransaction().add(R.id.containerb, secondFragment, "2").hide(secondFragment).commit()
        supportFragmentManager.beginTransaction().add(R.id.containerb, firstFragment, "1").commit()

        if (finish.equals("true")){

            bottomNavigation?.setSelectedItemId(R.id.ordersFragment);
            supportFragmentManager.beginTransaction().hide(active).show(thirdFragment).commit()
            active = thirdFragment
        }


        bottomNavigation?.setOnNavigationItemReselectedListener {
            when (it.itemId) {
                R.id.Fragment1 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(firstFragment).commit()
                    active = firstFragment

                }
                R.id.Fragment2 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(secondFragment).commit()
                    active = secondFragment

                }
                R.id.Fragment3 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(thirdFragment).commit()
                    active = thirdFragment

                }
                R.id.Fragment4 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(forthFragment).commit()
                    active = forthFragment

                }
            }
            true
        }


        bottomNavigation?.setOnNavigationItemSelectedListener { item ->
            when (item.itemId) {
                R.id.Fragment1 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(firstFragment).commit()
                    active = firstFragment

                }
                R.id.Fragment2 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(secondFragment).commit()
                    active = secondFragment
                }
                R.id.Fragment3 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(thirdFragment).commit()
                    active = thirdFragment
                }
                R.id.Fragment4 -> {
                    supportFragmentManager.beginTransaction().hide(active).show(forthFragment).commit()
                    active = forthFragment
                }
            }
            true
        }

    }

我什么时候收到这个错误？

在完成最后一个 activity 并且用户向后导航后，用户可以收到通知，当通知请求上下文时，错误从这个方法开始，我已经尝试过 requireContext(), this@..Activity, applicationContext, activity.context，以及所有可能性获取上下文这是 Fragment3

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        createNotificationChannele()
}
private fun newOrderOffers() {
        val uid = FirebaseAuth.getInstance().uid ?: ""
        val firestore = FirebaseFirestore.getInstance()
        val fireRef = firestore.collection("inProcess").whereEqualTo("userUid", uid)
        fireRef.addSnapshotListener { value, error ->
            if (value != null) {
                value.documentChanges.forEach {
                    if (it.type == DocumentChange.Type.ADDED) {

                        SendNotificationWhenSelected()

                    }
                }
            }
        }

    }

private fun createNotificationChannele(){
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
            val channel = NotificationChannel(chanal_id, chanale_name,
                NotificationManager.IMPORTANCE_HIGH).apply {
                lightColor = Color.RED
                enableLights(true)
            }
            val manager = this.context?.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            manager.createNotificationChannel(channel)
        }

    }
private fun SendNotificationWhenSelected(){
        val notification =
            NotificationCompat.Builder(requireContext(), chanal_id) // the error in this line
                .setContentTitle("...")
                .setContentText("....")
                .setSmallIcon(R.drawable.....)
                .setPriority(Notification.PRIORITY_HIGH)
                .setAutoCancel(true)
                .build()

        val notificationManager = NotificationManagerCompat.from(requireView().context)
        notificationManager.notify(notification_id, notification)
}

logcat 错误

java.lang.IllegalStateException: Fragment Fragment3{3131d71} (ee9f090f-fa37-46a0-9fda-b7e9831db10d)} not attached to an activity.
        at androidx.fragment.app.Fragment.requireActivity(Fragment.java:833)
        at com.qp.dele.fragment.Fragment3.SendNotificationWhenSelected(3Fragment.kt:295)
        at com.qp.dele.fragment.Fragment3.access$SendNotificationWhenSelected(Fragment3.kt:40)
        at com.qp.dele.fragment.Fragment3$newOrderOffers.onEvent(Fragment3.kt:272)
        at com.qp.dele.fragment.Fragment3$newOrderOffers.onEvent(Fragment3.kt:40)
        at com.google.firebase.firestore.Query.lambda$addSnapshotListenerInternal(Query.java:1133)
        at com.google.firebase.firestore.Query$$Lambda.onEvent(Unknown Source:6)
        at com.google.firebase.firestore.core.AsyncEventListener.lambda$onEvent[=14=](AsyncEventListener.java:42)
        at com.google.firebase.firestore.core.AsyncEventListener$$Lambda.run(Unknown Source:6)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Answer 1

看起来问题在于旧的 Fragment 仍然存在，并且在与旧的 Activity 分离后仍在获取 Firebase 回调。当旧 Fragment 为 detached/destroyed.

时，您需要删除 Firebase 回调

这就是为什么您在 return 返回 TabbarActivity 时会看到此问题，但在您首次启动应用程序时却不会。

如何重新附加片段（片段未附加到 activity Kotlin）

How to reattach Fragment (fragment Not not attached to an activity Kotlin)

android

android-fragments

android-activity

kotlin