片段中的 ViewPager2 在通过导航组件导航替换其所在的片段后泄漏
ViewPager2 inside a fragment leaks after replacing the fragment it's in by Navigation Component navigate
起初，我在 BottomNavigationView 和数据绑定的选项卡内遇到了 ViewPager2 的问题，数据绑定也与 ViewPager2 一起泄漏，应该在 [=20= 中取消]，泄漏并设法将问题缩小到 ViewPager2，同时使用 findNavController().navigate.
从包含 ViewPager2 的片段导航到另一个片段
它是这样发生的，它发生在我导航到另一个用 ViewPager2 替换当前片段的片段时。
这是代码
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
activity_main.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"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.fragment.app.FragmentContainerView
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
nav_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<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_parent"
app:startDestination="@id/parent_dest">
<fragment
android:id="@+id/parent_dest"
android:name="com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.viewpagerfragment.ViewPagerContainerFragment"
android:label="MainFragment"
tools:layout="@layout/fragment_viewpager_container">
<!-- Login -->
<action
android:id="@+id/action_main_dest_to_loginFragment2"
app:destination="@id/loginFragment2" />
</fragment>
<!-- Login -->
<fragment
android:id="@+id/loginFragment2"
android:name="com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.blankfragment.LoginFragment2"
android:label="LoginFragment2"
tools:layout="@layout/fragment_login2"/>
</navigation>
包含 ViewPager2 和 TabLayout
的片段
class ViewPagerContainerFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_viewpager_container, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// ViewPager2
val viewPager = view.findViewById<ViewPager2>(R.id.viewPager)
/*
Set Adapter for ViewPager inside this fragment using this Fragment,
more specifically childFragmentManager as param
*/
viewPager.adapter = ChildFragmentStateAdapter(this)
// TabLayout
val tabLayout = view.findViewById<TabLayout>(R.id.tabLayout)
// Bind tabs and viewpager
TabLayoutMediator(tabLayout, viewPager) { tab, position ->
when (position) {
0 -> tab.text = "Home"
1 -> tab.text = "Dashboard"
2 -> tab.text = "Notification"
3 -> tab.text = "Login"
}
}.attach()
}
}
fragment_viewpager_container
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.material.tabs.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:tabMode="scrollable" />
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tabLayout" />
</androidx.constraintlayout.widget.ConstraintLayout>
片段没什么特别的，但我添加了一种布局，也许 Material 小部件泄漏，我不知道
<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/fragment_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorHome1"
android:padding="8dp">
<com.google.android.material.textview.MaterialTextView
android:id="@+id/tvTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Home Fragment1"
android:textColor="#fff"
android:textSize="32sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.3" />
<com.google.android.material.button.MaterialButton
android:id="@+id/btnNextPage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Next Page"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvTitle" />
</androidx.constraintlayout.widget.ConstraintLayout>
以及来自 Leak Canary 的堆转储
┬───
│ GC Root: System class
│
├─ android.app.ActivityThread class
│ Leaking: NO (MainActivity↓ is not leaking and a class is never leaking)
│ ↓ static ActivityThread.sCurrentActivityThread
├─ android.app.ActivityThread instance
│ Leaking: NO (MainActivity↓ is not leaking)
│ ↓ ActivityThread.mTopActivityClient
├─ android.app.ActivityThread$ActivityClientRecord instance
│ Leaking: NO (MainActivity↓ is not leaking)
│ ↓ ActivityThread$ActivityClientRecord.activity
├─ com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.MainActivity instance
│ Leaking: NO (NavHostFragment↓ is not leaking and Activity#mDestroyed is false)
│ ↓ MainActivity.mFragments
├─ androidx.fragment.app.FragmentController instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentController.mHost
├─ androidx.fragment.app.FragmentActivity$HostCallbacks instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentActivity$HostCallbacks.mFragmentManager
├─ androidx.fragment.app.FragmentManagerImpl instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentManagerImpl.mPrimaryNav
├─ androidx.navigation.fragment.NavHostFragment instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking and Fragment#mFragmentManager is not null)
│ ↓ NavHostFragment.mChildFragmentManager
├─ androidx.fragment.app.FragmentManagerImpl instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentManagerImpl.mFragmentStore
├─ androidx.fragment.app.FragmentStore instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentStore.mActive
├─ java.util.HashMap instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap.table
├─ java.util.HashMap$Node[] array
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap$Node[].[0]
├─ java.util.HashMap$Node instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap$Node.value
├─ androidx.fragment.app.FragmentStateManager instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentStateManager.mFragment
├─ com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.viewpagerfragment.ViewPagerContainerFragment instance
│ Leaking: NO (Fragment#mFragmentManager is not null)
│ ↓ ViewPagerContainerFragment.mLifecycleRegistry
│ ~~~~~~
├─ androidx.lifecycle.LifecycleRegistry instance
│ Leaking: UNKNOWN
│ ↓ LifecycleRegistry.mObserverMap
│ ~~~~
├─ androidx.arch.core.internal.FastSafeIterableMap instance
│ Leaking: UNKNOWN
│ ↓ FastSafeIterableMap.mEnd
│ ~~
├─ androidx.arch.core.internal.SafeIterableMap$Entry instance
│ Leaking: UNKNOWN
│ ↓ SafeIterableMap$Entry.mKey
│ ~~
├─ androidx.viewpager2.adapter.FragmentStateAdapter$FragmentMaxLifecycleEnforcer instance
│ Leaking: UNKNOWN
│ Anonymous class implementing androidx.lifecycle.LifecycleEventObserver
│ ↓ FragmentStateAdapter$FragmentMaxLifecycleEnforcer.this
│ ~~
├─ androidx.viewpager2.adapter.FragmentStateAdapter$FragmentMaxLifecycleEnforcer instance
│ Leaking: UNKNOWN
│ ↓ FragmentStateAdapter$FragmentMaxLifecycleEnforcer.mViewPager
│ ~~~~
├─ androidx.viewpager2.widget.ViewPager2 instance
│ Leaking: YES (View detached and has parent)
│ mContext instance of com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.MainActivity with mDestroyed = false
│ View#mParent is set
│ View#mAttachInfo is null (view detached)
│ View.mID = R.id.viewPager
│ View.mWindowAttachCount = 1
│ ↓ ViewPager
如果您想自己检查或重现问题，我还会添加 github link。
在片段的 onDestroyView 方法中从 ViewPager2 中删除适配器解决了 FragmentStateAdapter
的内存泄漏问题
override fun onDestroyView() {
val viewPager2 = dataBinding?.viewPager
viewPager2?.let {
it.adapter = null
}
super.onDestroyView()
}
还在片段的 onDestroyView 中将数据绑定设置为 null，我在基本片段中进行了设置，这导致了与数据绑定相关的内存泄漏。或如前所述here用于viewBinding，它适用于数据绑定。
private var _binding: ResultProfileBinding? = null
// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = ResultProfileBinding.inflate(inflater, container, false)
val view = binding.root
return view
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
Note: Fragments outlive their views. Make sure you clean up any
references to the binding class instance in the fragment's
onDestroyView() method.
另一个防止片段中 ViewPager2 内存泄漏的方法是使用 viewLifeCycleOwner 的生命周期，它在 onCreateView 和 onDestroyView 之间而不是 this 与提到的 FragmentStateAdapter here.
FragmentManager fm = getChildFragmentManager();
Lifecycle lifecycle = getViewLifecycleOwner().getLifecycle();
fragmentAdapter = new FragmentAdapter(fm, lifecycle);
起初，我在 BottomNavigationView 和数据绑定的选项卡内遇到了 ViewPager2 的问题，数据绑定也与 ViewPager2 一起泄漏，应该在 [=20= 中取消]，泄漏并设法将问题缩小到 ViewPager2，同时使用 findNavController().navigate.
它是这样发生的，它发生在我导航到另一个用 ViewPager2 替换当前片段的片段时。
这是代码
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
}
activity_main.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"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.fragment.app.FragmentContainerView
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
</androidx.constraintlayout.widget.ConstraintLayout>
nav_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<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_parent"
app:startDestination="@id/parent_dest">
<fragment
android:id="@+id/parent_dest"
android:name="com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.viewpagerfragment.ViewPagerContainerFragment"
android:label="MainFragment"
tools:layout="@layout/fragment_viewpager_container">
<!-- Login -->
<action
android:id="@+id/action_main_dest_to_loginFragment2"
app:destination="@id/loginFragment2" />
</fragment>
<!-- Login -->
<fragment
android:id="@+id/loginFragment2"
android:name="com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.blankfragment.LoginFragment2"
android:label="LoginFragment2"
tools:layout="@layout/fragment_login2"/>
</navigation>
包含 ViewPager2 和 TabLayout
class ViewPagerContainerFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
return inflater.inflate(R.layout.fragment_viewpager_container, container, false)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// ViewPager2
val viewPager = view.findViewById<ViewPager2>(R.id.viewPager)
/*
Set Adapter for ViewPager inside this fragment using this Fragment,
more specifically childFragmentManager as param
*/
viewPager.adapter = ChildFragmentStateAdapter(this)
// TabLayout
val tabLayout = view.findViewById<TabLayout>(R.id.tabLayout)
// Bind tabs and viewpager
TabLayoutMediator(tabLayout, viewPager) { tab, position ->
when (position) {
0 -> tab.text = "Home"
1 -> tab.text = "Dashboard"
2 -> tab.text = "Notification"
3 -> tab.text = "Login"
}
}.attach()
}
}
fragment_viewpager_container
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.material.tabs.TabLayout
android:id="@+id/tabLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:tabMode="scrollable" />
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tabLayout" />
</androidx.constraintlayout.widget.ConstraintLayout>
片段没什么特别的，但我添加了一种布局，也许 Material 小部件泄漏，我不知道
<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/fragment_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorHome1"
android:padding="8dp">
<com.google.android.material.textview.MaterialTextView
android:id="@+id/tvTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Home Fragment1"
android:textColor="#fff"
android:textSize="32sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.3" />
<com.google.android.material.button.MaterialButton
android:id="@+id/btnNextPage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Next Page"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvTitle" />
</androidx.constraintlayout.widget.ConstraintLayout>
以及来自 Leak Canary 的堆转储
┬───
│ GC Root: System class
│
├─ android.app.ActivityThread class
│ Leaking: NO (MainActivity↓ is not leaking and a class is never leaking)
│ ↓ static ActivityThread.sCurrentActivityThread
├─ android.app.ActivityThread instance
│ Leaking: NO (MainActivity↓ is not leaking)
│ ↓ ActivityThread.mTopActivityClient
├─ android.app.ActivityThread$ActivityClientRecord instance
│ Leaking: NO (MainActivity↓ is not leaking)
│ ↓ ActivityThread$ActivityClientRecord.activity
├─ com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.MainActivity instance
│ Leaking: NO (NavHostFragment↓ is not leaking and Activity#mDestroyed is false)
│ ↓ MainActivity.mFragments
├─ androidx.fragment.app.FragmentController instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentController.mHost
├─ androidx.fragment.app.FragmentActivity$HostCallbacks instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentActivity$HostCallbacks.mFragmentManager
├─ androidx.fragment.app.FragmentManagerImpl instance
│ Leaking: NO (NavHostFragment↓ is not leaking)
│ ↓ FragmentManagerImpl.mPrimaryNav
├─ androidx.navigation.fragment.NavHostFragment instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking and Fragment#mFragmentManager is not null)
│ ↓ NavHostFragment.mChildFragmentManager
├─ androidx.fragment.app.FragmentManagerImpl instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentManagerImpl.mFragmentStore
├─ androidx.fragment.app.FragmentStore instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentStore.mActive
├─ java.util.HashMap instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap.table
├─ java.util.HashMap$Node[] array
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap$Node[].[0]
├─ java.util.HashMap$Node instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ HashMap$Node.value
├─ androidx.fragment.app.FragmentStateManager instance
│ Leaking: NO (ViewPagerContainerFragment↓ is not leaking)
│ ↓ FragmentStateManager.mFragment
├─ com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.viewpagerfragment.ViewPagerContainerFragment instance
│ Leaking: NO (Fragment#mFragmentManager is not null)
│ ↓ ViewPagerContainerFragment.mLifecycleRegistry
│ ~~~~~~
├─ androidx.lifecycle.LifecycleRegistry instance
│ Leaking: UNKNOWN
│ ↓ LifecycleRegistry.mObserverMap
│ ~~~~
├─ androidx.arch.core.internal.FastSafeIterableMap instance
│ Leaking: UNKNOWN
│ ↓ FastSafeIterableMap.mEnd
│ ~~
├─ androidx.arch.core.internal.SafeIterableMap$Entry instance
│ Leaking: UNKNOWN
│ ↓ SafeIterableMap$Entry.mKey
│ ~~
├─ androidx.viewpager2.adapter.FragmentStateAdapter$FragmentMaxLifecycleEnforcer instance
│ Leaking: UNKNOWN
│ Anonymous class implementing androidx.lifecycle.LifecycleEventObserver
│ ↓ FragmentStateAdapter$FragmentMaxLifecycleEnforcer.this
│ ~~
├─ androidx.viewpager2.adapter.FragmentStateAdapter$FragmentMaxLifecycleEnforcer instance
│ Leaking: UNKNOWN
│ ↓ FragmentStateAdapter$FragmentMaxLifecycleEnforcer.mViewPager
│ ~~~~
├─ androidx.viewpager2.widget.ViewPager2 instance
│ Leaking: YES (View detached and has parent)
│ mContext instance of com.smarttoolfactory.tutorial6_7navigationui_memoryleakcheck.MainActivity with mDestroyed = false
│ View#mParent is set
│ View#mAttachInfo is null (view detached)
│ View.mID = R.id.viewPager
│ View.mWindowAttachCount = 1
│ ↓ ViewPager
如果您想自己检查或重现问题，我还会添加 github link。
在片段的 onDestroyView 方法中从 ViewPager2 中删除适配器解决了 FragmentStateAdapter
override fun onDestroyView() {
val viewPager2 = dataBinding?.viewPager
viewPager2?.let {
it.adapter = null
}
super.onDestroyView()
}
还在片段的 onDestroyView 中将数据绑定设置为 null，我在基本片段中进行了设置，这导致了与数据绑定相关的内存泄漏。或如前所述here用于viewBinding，它适用于数据绑定。
private var _binding: ResultProfileBinding? = null
// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = ResultProfileBinding.inflate(inflater, container, false)
val view = binding.root
return view
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
Note: Fragments outlive their views. Make sure you clean up any references to the binding class instance in the fragment's onDestroyView() method.
另一个防止片段中 ViewPager2 内存泄漏的方法是使用 viewLifeCycleOwner 的生命周期，它在 onCreateView 和 onDestroyView 之间而不是 this 与提到的 FragmentStateAdapter here.
FragmentManager fm = getChildFragmentManager();
Lifecycle lifecycle = getViewLifecycleOwner().getLifecycle();
fragmentAdapter = new FragmentAdapter(fm, lifecycle);