调用findNavController().popBackStack()不会恢复堆栈上的前一个片段
调用findNavController().popBackStack()不会恢复堆栈上的前一个片段
提问于 2022-02-03 23:47:05
我刚刚设置了一个带有Android导航组件的projet，下面是我的图表结构：
<navigation 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/nav_graph"
app:startDestination="@id/a">
<fragment
android:id="@+id/a"
android:name="com.example.tutorial.fragmentA"
android:label="a">
<action android:id="@+id/action_a_to_b"
app:destination="@id/b"
app:enterAnim="@anim/nav_default_enter_anim"
app:exitAnim="@anim/nav_default_exit_anim"
app:popEnterAnim="@anim/nav_default_pop_enter_anim"
app:popExitAnim="@anim/nav_default_pop_exit_anim"/>
</fragment>
<fragment
android:id="@+id/b"
android:name="com.example.tutorial.fragmentB"
android:label="b">
</fragment>
</navigation>在片段A中，我像这样导航到B：
findNavController().navigate(R.id.action_a_to_b)在片段B中，我有一个自定义工具栏，其想法是单击左上角箭头应该关闭片段B并恢复A：
(activity as AppCompatActivity).setSupportActionBar(binding.toolbar)
binding.toolbar.setNavigationOnClickListener {
findNavController().popBackStack()
}如果我点击按下键按钮，情况也是一样：
requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner){
findNavController().popBackStack()
}我仍然困在片段B中的问题:退出动画开始和结束，而我仍然在片段B中。有什么办法来解决这个问题吗？
回答 3
Stack Overflow用户
发布于 2022-02-04 00:00:07
我创建了一个包含两个片段的小项目，它没有流程。我们有一个登录屏幕和一个带有密码的屏幕。
LoginFragment
class LoginFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_login, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val toolbar = view.findViewById<androidx.appcompat.widget.Toolbar>(R.id.loginToolbar)
toolbar.navigationIcon = null
// Set the Toolbar as your activity's ActionBar
(requireActivity() as AppCompatActivity).setSupportActionBar(toolbar)
// Find this Fragment's NavController
val navController = NavHostFragment.findNavController(this);
// And set up the ActionBar
NavigationUI.setupActionBarWithNavController(
requireActivity() as AppCompatActivity,
navController
)
val b = view.findViewById<MaterialButton>(R.id.loginButton)
b.setOnClickListener {
this.findNavController().navigate(R.id.passwordsFragment)
}
}
}PasswordFragment
class PasswordsFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_passwords, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val toolbar = view.findViewById<androidx.appcompat.widget.Toolbar>(R.id.myToolbar)
// Set the Toolbar as your activity's ActionBar
(requireActivity() as AppCompatActivity).setSupportActionBar(toolbar)
// Find this Fragment's NavController
val navController = NavHostFragment.findNavController(this);
// And set up the ActionBar
NavigationUI.setupActionBarWithNavController(
requireActivity() as AppCompatActivity,
navController
)
toolbar.setNavigationOnClickListener {
navController.navigateUp()
}
}
}LoginFragment XML中的工具栏
<androidx.appcompat.widget.Toolbar
android:id="@+id/loginToolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/black"
app:layout_constraintTop_toTopOf="parent" />PasswordFragment XML中的工具栏
<androidx.appcompat.widget.Toolbar
android:id="@+id/myToolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/black"
app:layout_constraintTop_toTopOf="parent" />MainActivity XML
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/constraintLayout3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:elevation="6dp"
android:fillViewport="true"
android:orientation="vertical">
<androidx.fragment.app.FragmentContainerView
android:id="@+id/my_nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>我从loginFragment导航到PasswordFragment，然后按up按钮，然后进入前面的片段:)
如果能用，请告诉我。
Stack Overflow用户
发布于 2022-03-17 07:08:43
private lateinit var appBarConfiguration: AppBarConfiguration
//onCreate
val navHostFragment =
supportFragmentManager.findFragmentById(R.id.fragment4) as NavHostFragment
val navController = navHostFragment.navController
appBarConfiguration = AppBarConfiguration(navController.graph, drawerLayout)
setupActionBarWithNavController(navController, appBarConfiguration)
navDrawView.setupWithNavController(navController)
bottomAppBar.background = null
bottomAppBar.setupWithNavController(navController)
//automatic NavigateUp setup
override fun onSupportNavigateUp(): Boolean {
val navController = findNavController(R.id.fragment4)
return navController.navigateUp(appBarConfiguration)
|| super.onSupportNavigateUp()
}你能在你的主要活动中尝试这个设置吗，它为我工作，我使用bottomNav导航抽屉和appbar在一起。
如果您想使用自定义工具栏
//in fragment or activity
private fun handleToolbarChanges() {
with(binding.toolbarDataAnalysis) {
setNavigationOnClickListener { onBackPressed() }
title = "your title here"
}
}
//in xml file
<androidx.appcompat.widget.Toolbar
android:id="@+id/toolbarDataAnalysis"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/green"
app:navigationIcon="@drawable/ic_baseline_arrow_back_24"
app:titleTextColor="@color/white" />Stack Overflow用户
发布于 2022-07-21 12:16:21
现在，我们可以使用popBackStack()为第二个片段的返回值创建观察者
假设我们有，firstFragment，和firstFragment
在firstFragment中，使用这个作为观察者:-
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
val navController = findNavController()
navController.currentBackStackEntry?.savedStateHandle?.getLiveData<String>("isDelete")
?.observe(viewLifecycleOwner) {
if(it.lowercase().compareTo("true")==0)
{
//write code here
}
else
{
//write code here
}
}
}在secondFragment中使用以下代码
val navController = findNavController()
navController.previousBackStackEntry?.savedStateHandle?.set("isDelete", "true/false")
navController.popBackStack()页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/70979880
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