将自动完成片段放在无法启动活动的片段中

Question

我已经在活动中使用 Google Places API 实现了AutoCompleteFragment，但是当我尝试在片段中实现它时，返回无法启动活动错误。

片段与DrawerMenu处于MainActivity中

日志猫：

2020-06-23 20:19:14.240 5546-5546/com.aitorramos.dogtravel E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.aitorramos.dogtravel, PID: 5546
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.aitorramos.dogtravel/com.aitorramos.dogtravel.MainActivity}: kotlin.KotlinNullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: kotlin.KotlinNullPointerException
at com.aitorramos.dogtravel.Fragments.SearchFragment.setupAutoComplete(SearchFragment.kt:59)
at com.aitorramos.dogtravel.Fragments.SearchFragment.onCreateView(SearchFragment.kt:45)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2600)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:881)
at androidx.fragment.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManagerImpl.java:1238)
at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManagerImpl.java:1303)
at androidx.fragment.app.BackStackRecord.executeOps(BackStackRecord.java:439)
at androidx.fragment.app.FragmentManagerImpl.executeOps(FragmentManagerImpl.java:2079)
at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManagerImpl.java:1869)
at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManagerImpl.java:1824)
at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManagerImpl.java:1727)
at androidx.fragment.app.FragmentManagerImpl.dispatchStateChange(FragmentManagerImpl.java:2663)
at androidx.fragment.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManagerImpl.java:2613)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:246)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:542)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:201)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1333)
at android.app.Activity.performStart(Activity.java:6992)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2780)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
at android.app.ActivityThread.-wrap11(Unknown Source:0) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
at android.os.Handler.dispatchMessage(Handler.java:105) 
at android.os.Looper.loop(Looper.java:164) 
at android.app.ActivityThread.main(ActivityThread.java:6541) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 

SearchFragment.kt：

override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
// Inflate the layout for this fragment
_view = inflater.inflate(R.layout.fragment_search, container, false)
setupAutoComplete(R.id.gCityFrom, 0)
return view
}
private fun setupAutoComplete(fragment: Int, flag: Int){
if (!Places.isInitialized()) {
Places.initialize(requireContext(), apiKey)
}

//Return null
val autocompleteFragment = fragmentManager!!.findFragmentById(fragment) as AutocompleteSupportFragment?
//error here
autocompleteFragment!!.setPlaceFields(Arrays.asList(Place.Field.ID, Place.Field.NAME, Place.Field.LAT_LNG)) 
.....

fragment_search.xml

<androidx.cardview.widget.CardView
android:id="@+id/cardView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:layout_marginEnd="16dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<fragment
android:id="@+id/gCityFrom"
android:name="com.google.android.libraries.places.widget.AutocompleteSupportFragment"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</androidx.cardview.widget.CardView>

Answer 1

试试

val autocompleteFragment = fragmentManager!!.findFragmentById(R.id.gCityFrom) as AutocompleteSupportFragment?

而不是

val autocompleteFragment = fragmentManager!!.findFragmentById(fragment) as AutocompleteSupportFragment?

Answer 2

使用

val autocompleteFragment = childFragmentManager.findFragmentById(fragment) as AutocompleteSupportFragment?