问题
i am using Advance Navigation Component with BottomNavigationView, In One tab i have viewPager2 first clicked on tab is working fine but second time come on that tab application keep crashing. Below is crashlog if anyone can help thanks.
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$4.run(FragmentManager.java:413) at android.os.Handler.handleCallback(Handler.java:873) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:193) at android.app.ActivityThread.main(ActivityThread.java:6940) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
Here is my code for fragment :
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)
}
})
}
Here is ui code :
<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>
Here is my adapter code:
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()
}
}
}
回答1:
Actual error is of the lazy initialisation of the adapter. I also don't know why that happened
回答2:
Had the same crash with my ViewPager2 implementation. In my case I was creating adapter in onCreate and setting it to ViewPager in onViewCreated. Like this:
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
}
I've fixed crash combining adapter creation and setting into one method - onViewCreated. Like this:
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
adapter = FragmentAdapter(this, month)
binding?.viewPager?.adapter = adapter
}
回答3:
Try out this solution.
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()
}
}
code for fragment
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
}
})
回答4:
I had the same error when i get back to the fragment, and i solved the problem after i read @Oleh comment that said: 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
so i set the adapter to null in onPause like this code , then the problem is disappeared:
override fun onPause() {
super.onPause()
binding?.run {
viewPager.adapter = null
}
}
来源：https://stackoverflow.com/questions/61606656/viewpager2-crash