我正在嘗試在某些條件下使用從我的主片段導航到相應片段的導航來開發單活動應用程式（請參閱下面的代碼片段）。但是當我使用條件啟動應用程式時isLoggedIn == true，會出現例外：
2022-05-01 17:42:22.888 14974-14974/com.example.shercofaqapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.shercofaqapp, PID: 14974
java.lang.IllegalStateException: Fragment LoginFragment{d69320f} (2bebfc01-ce4e-435e-be4f-821b5d142eb8 id=0x7f0a0096) did not return a View from onCreateView() or this was called before onCreateView().
at androidx.fragment.app.Fragment.requireView(Fragment.java:2008)
at com.example.shercofaqapp.view.LoginFragment.onCreateView(LoginFragment.kt:47)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2995)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:523)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:113)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1374)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2841)
at androidx.fragment.app.FragmentManager.dispatchViewCreated(FragmentManager.java:2777)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:3020)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:551)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:113)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1374)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2841)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2784)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:262)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:478)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:246)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425)
at android.app.Activity.performStart(Activity.java:7825)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
這是我的代碼片段：
package com.example.shercofaqapp.view
import android.content.Context
import android.os.Bundle
import android.text.TextUtils
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Toast
import androidx.databinding.DataBindingUtil
import androidx.navigation.Navigation
import com.example.shercofaqapp.R
import com.example.shercofaqapp.databinding.FragmentLoginBinding
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import kotlin.properties.Delegates
class LoginFragment : Fragment() {
lateinit var binding: FragmentLoginBinding
private var isLoggedIn by Delegates.notNull<Boolean>()
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
val sharedPref = requireActivity()
.getSharedPreferences("MyPreferences", Context.MODE_PRIVATE)
val editor = sharedPref.edit()
var isLoggingIn = false
binding = DataBindingUtil.inflate(
inflater, R.layout.fragment_login, container, false)
binding.apply {
//Log in / sign up logic
isLoggedIn = sharedPref.getBoolean("isLoggedIn", false)
if (isLoggedIn) {
Navigation.findNavController(requireView())
.navigate(R.id.action_loginFragment_to_garageFragment)
}
}
return binding.root
}
}問題是：我怎樣才能在回傳view之前獲得導航onCreateView()？
我嘗試使用此解決方案，但我不明白.findNavController(...)在我的情況下我應該傳遞什么論點。
PS NavHostFragment 在 MainActivity 中：
<?xml version="1.0" encoding="utf-8"?>
<layout
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"
tools:context=".MainActivity">
<androidx.fragment.app.FragmentContainerView
android:id="@ id/containerView"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
</layout>
uj5u.com熱心網友回復：
根據Navigate to a destination 檔案，您應該使用findNavController()Kotlin 擴展Fragment，它是呼叫的便捷包裝器NavHostFragment.findNavController(this)：
binding.apply {
//Log in / sign up logic
isLoggedIn = sharedPref.getBoolean("isLoggedIn", false)
if (isLoggedIn) {
// Make sure to:
// 1. Add a dependency on navigation-fragment-ktx in your build.gradle
// 2. import androidx.navigation.fragment.findNavController
findNavController()
.navigate(R.id.action_loginFragment_to_garageFragment)
}
}
uj5u.com熱心網友回復：
findNavController(requireActivity()) .navigate(R.id.action_loginFragment_to_garageFragment)
使用此行代碼，我認為它對您有幫助
轉載請註明出處，本文鏈接：https://www.uj5u.com/qianduan/469418.html