ViewPager2 崩溃

Question

我正在使用带 BottomNavigationView 的高级导航组件。

在 一个选项卡中 我有 ViewPager2。当我第一次点击标签时，它运行良好。

尽管是第二次，但该选项卡应用程序一直崩溃。下面是崩溃日志。我该如何解决这个问题？

java.lang.IllegalArgumentException
at androidx.core.util.Preconditions.checkArgument(Preconditions.java:36)
at androidx.viewpager2.adapter.FragmentStateAdapter.onAttachedToRecyclerView(FragmentStateAdapter.java:140)
at androidx.recyclerview.widget.RecyclerView.setAdapterInternal(RecyclerView.java:1206)
at androidx.recyclerview.widget.RecyclerView.setAdapter(RecyclerView.java:1158)
at androidx.viewpager2.widget.ViewPager2.setAdapter(ViewPager2.java:460)
at com..ui.home.history.HistoryFragment.setupAdapter(HistoryFragment.kt:25)
at com..ui.home.history.HistoryFragment.viewSetup(HistoryFragment.kt:21)
at com.****.base.BaseFragment.onViewCreated(BaseFragment.kt:37)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:332)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1356)
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1434)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1497)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2625)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2577)
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2722)
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1188)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1997)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
at androidx.fragment.app.FragmentManager.run(FragmentManager.java:413)
at android.os.Handler.handleCallback(Handler.java:873)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:6940)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

这是我的片段代码：

private val adapter by lazy {
    HistoryPagerAdapter(this)
}

override fun viewSetup() {
    binding.vpBuySell.adapter = adapter
    TabLayoutMediator(
        binding.tabBuySell,
        binding.vpBuySell,
        TabLayoutMediator.TabConfigurationStrategy { tab: TabLayout.Tab, i: Int ->
           tab.text = when (i) {
                0 -> getString(R.string.buy)
                1 -> getString(R.string.sell)
                else -> getString(R.string.buy)
            }
        })
}

这里是 UI 代码：

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/blue_122e47">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?actionBarSize"
        android:background="@color/blue_06233e"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:titleTextColor="@color/white">

        <androidx.appcompat.widget.AppCompatTextView
            android:id="@+id/tvTitle"
            style="@style/ToolbarTitleTextStyle"
            android:text="@string/history" />

        <TextView
            android:id="@+id/btnExport"
            android:layout_width="wrap_content"
            android:layout_height="@dimen/_24sdp"
            android:layout_gravity="end"
            android:layout_marginEnd="@dimen/_8sdp"
            android:fontFamily="@font/helvetica_neue_medium"
            android:insetLeft="0dp"
            android:gravity="center"
            android:background="@drawable/shape_export_button"
            android:insetTop="0dp"
            android:insetRight="0dp"
            android:insetBottom="0dp"
            android:foreground="?selectableItemBackground"
            android:paddingBottom="@dimen/_2sdp"
            android:paddingStart="@dimen/_8sdp"
            android:paddingEnd="@dimen/_8sdp"
            android:text="@string/export"
            android:textAllCaps="false"
            android:textColor="@color/white"
            android:textSize="@dimen/_12ssp" />

    </androidx.appcompat.widget.Toolbar>


    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabBuySell"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/blue_122e47"
        app:tabIndicatorFullWidth="false"
        app:tabIndicatorGravity="bottom"
        app:tabTextAppearance="@style/HistoryTabTextStyle"
        app:tabTextColor="@color/gray_697b8b"
        app:tabSelectedTextColor="@color/white"
        app:tabIndicatorHeight="@dimen/_2sdp"
        app:tabIndicatorColor="@color/blue_47cfff"
        app:layout_constraintTop_toBottomOf="@id/toolbar"
        app:tabGravity="start"
        app:tabMode="scrollable" />

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/vpBuySell"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="@id/tabBuySell" />

</androidx.constraintlayout.widget.ConstraintLayout>

这是我的适配器代码：

class HistoryPagerAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {

    override fun getItemCount(): Int {
        return 2
    }

    override fun createFragment(position: Int): Fragment {
        return when (position) {
            0 -> HistoryBuyFragment()
            1 -> HistorySellFragment()
            else -> HistoryBuyFragment()
        }
    }

}

Answer 1

试试这个解决方案：

import androidx.viewpager2.adapter.FragmentStateAdapter

class HistoryPagerAdapter(activity: AppCompatActivity, private var itemCount: Int): FragmentStateAdapter(activity) {

    override fun getItemCount(): Int {
        return 2
    }

    override fun createFragment(position: Int): Fragment {
        return when (position) {
            0 -> HistoryBuyFragment()
            1 -> HistorySellFragment()
            else -> HistoryBuyFragment()
        }
    }

片段代码：

private val TAB_ITEMS_COUNT = 2

adapter = HistoryPagerAdapter((activity as AppCompatActivity), TAB_ITEMS_COUNT)
binding.vpBuySell.adapter = adapter

TabLayoutMediator(binding.tabBuySell, binding.vpBuySell) { tab, position ->
    when(position)
    {
        0 -> tab.text = getString(R.string.buy)
        1 -> tab.text = getString(R.string.sell)
    }
}.attach()

binding.tabBuySell.addOnTabSelectedListener(object: TabLayout.OnTabSelectedListener
{
    override fun onTabReselected(tabItem: TabLayout.Tab?) {}
    override fun onTabUnselected(tabItem: TabLayout.Tab?) {}
    override fun onTabSelected(tabItem: TabLayout.Tab) {
        binding.vpBuySell.currentItem = tabItem.position
    }
})

Answer 2

实际错误是适配器的延迟初始化。我也不知道为什么会这样。

Answer 3

我的 ViewPager2 实现也遇到了同样的崩溃。在我的例子中，我在 onCreate 中创建了一个适配器，并在 onViewCreated 中将其设置为 ViewPager。像这样：

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    adapter = FragmentAdapter(this)
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    binding?.viewPager?.adapter = adapter
}

我已经修复了崩溃，将适配器创建和设置合并到一个方法中 - onViewCreated。像这样：

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    adapter = FragmentAdapter(this, month)
    binding?.viewPager?.adapter = adapter
}

Answer 4

当我回到片段时我有同样的错误，我在阅读后解决了这个问题说：

I assume that on a retained fragment lazy property cause memory leak because of holding a reference to the old view which leads to crash

于是我像这段代码在onPause中将adapter设置为null，然后问题就消失了：

override fun onPause() {
    super.onPause()
    binding?.run {
        viewPager.adapter = null
    }
}

Answer 5

当你设置viewpager2适配器时，首先检查viewpager已经适配器，否则设置适配器。

例如，

if(viewPager.adapter == null) {
     viewPager.adapter = adapter
}

Answer 6

如果您使用的是导航组件，则当您返回时会重新创建片段的视图。出于某种原因，在我的例子中，当片段的视图被销毁时，适配器没有自动分离。错误是：我保留了一个已经附加的适配器引用，并试图将它添加到一个新的寻呼机视图中。在我的案例中，在 onDestroyView() 中设置 adapter = null 有效。

override fun onDestroyView() {
    pager.adapter = null
    super.onDestroyView()
}

Answer 7

我运行在片段之间来回切换时遇到了 BottomNavigationView 的这个问题。问题是我使用了 Kotlin 的 by lazy {} 值定义，并且我在 onViewCreated 中设置了适配器。出于某种原因，无法正确恢复片段状态，即使我使用了此 post 中的一些“技巧”，如修改某些生命周期方法等，也无法设置适配器

寻呼机适配器在状态恢复期间自动恢复。这就是为什么您可能不想保留您的适配器，而是总是在 onViewCreated 中设置一个新的。然后就等着自动恢复触发，还有你之前的状态。

修复：

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

    // Anything you set here will be overriden during restoration
    viewBinding.pager.adapter = DemoCollectionPagerAdapter(this)

    var mediator = TabLayoutMediator(viewBinding.tabLayout, viewBinding.pager) { tab, position ->
        when (position){
            0 -> tab.text = getString(R.string.global_rooms).uppercase()
            1 -> tab.text = getString(R.string.global_devices).uppercase()
            2 -> tab.text = getString(R.string.global_presets).uppercase()
        }
    }.attach()
}

ViewPager2 崩溃

ViewPager2 crash

android

android-recyclerview

android-jetpack

android-jetpack-navigation

android-viewpager2

修复：