java - 如何解决 androidx.recyclerview.widget.RecyclerView$ViewHolder.shouldIgnore()' 上的 NullPointer 异常
问题描述
我在我的应用程序的 RecyclerView.java 代码中得到一个空异常指针。我在异常点附上了调试条目的屏幕截图。可以看到，执行 holder.shouldIngnore() 方法时，holder 对象为 null。
该应用程序在使用 tablayout 的活动中的另一个片段中具有两个片段（每个片段具有不同的回收器视图和 LiveData）。
我怀疑识别子片段存在问题，需要帮助解决。
已提供尽可能多的相关信息以提供帮助。这是我第一次尝试一个片段中的两个片段。
为了适应 StackOverFlow 的大小限制，我只包含了第一个子片段代码。第二个片段反映了第一个片段。
[![调试截图][2]][2]
日志猫条目
2020-04-02 07:44:27.814 10294-10294/com.grgapps.checkingin E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.grgapps.checkingin, PID: 10294
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean androidx.recyclerview.widget.RecyclerView$ViewHolder.shouldIgnore()' on a null object reference
at androidx.recyclerview.widget.RecyclerView.findMinMaxChildLayoutPositions(RecyclerView.java:4311)
at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:4045)
at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3849)
at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
at android.view.View.layout(View.java:17523)
at android.view.ViewGroup.layout(ViewGroup.java:5612)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:17523)
at android.view.ViewGroup.layout(ViewGroup.java:5612)
以下是活动选项卡中的框架布局 (fragment_check_in_new_recipients.xml)
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".CheckInNewRecipients">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<include layout="@layout/fragment_contacts_selection_list_display" />
<include layout="@layout/fragment_contacts_filter_and_display" />
</LinearLayout>
</FrameLayout>
以下是来自活动选项卡的框架内的第一个子框架 (fragment_contacts_selection_list_display.xml)。
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="200dp"
tools:context=".ContactsSelectionListDisplay">
<!-- TODO: Update blank fragment layout -->
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/check_in_recipient_selection_list_recycler_view"
android:layout_width="match_parent"
android:layout_height="200dp"
android:divider="#467FD7"
android:dividerHeight="10dp"
tools:listitem="@layout/recycler_view_check_in_recipient_selected_list"/>
</FrameLayout>
以下是选项卡片段中的第二个子片段 (fragment_contacts_filter_and_display.xml)。
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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:layout_width="match_parent"
android:layout_height="350dp"
tools:context=".ContactsFilterAndDisplay">
<!-- TODO: Update blank fragment layout -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="108dp">
<RadioGroup
android:layout_width="wrap_content"
android:layout_height="55dp"
android:orientation="horizontal">
</RadioGroup>
<RadioButton
android:id="@+id/radio_all_contacts"
android:layout_width="80dp"
android:layout_height="55dp"
android:layout_marginTop="44dp"
android:layout_marginEnd="328dp"
android:buttonTint="#2196F3"
android:drawableTint="#2196F3"
android:onClick="onRadioButtonClicked"
android:text="@string/radio_contact_filter_all"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<RadioButton
android:id="@+id/radio_app_users"
android:layout_width="100dp"
android:layout_height="55dp"
android:layout_marginTop="44dp"
android:layout_marginEnd="228dp"
android:buttonTint="#2196F3"
android:drawableTint="#2196F3"
android:onClick="onRadioButtonClicked"
android:text="@string/radio_contact_filter_app_users"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<RadioButton
android:id="@+id/radio_by_group"
android:layout_width="100dp"
android:layout_height="55dp"
android:layout_marginTop="44dp"
android:layout_marginEnd="120dp"
android:buttonTint="#2196F3"
android:drawableTint="#2196F3"
android:onClick="onRadioButtonClicked"
android:text="@string/radio_contact_filter_by_group"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<RadioButton
android:id="@+id/radio_filter_search"
android:layout_width="100dp"
android:layout_height="55dp"
android:layout_marginStart="304dp"
android:layout_marginTop="44dp"
android:buttonTint="#2196F3"
android:drawableTint="#2196F3"
android:onClick="onRadioButtonClicked"
android:text="@string/radio_contact_filter_search"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textView14"
android:layout_width="match_parent"
android:layout_height="30dp"
android:text="@string/title_contacts_filter"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/check_in_recipient_contacts_list_recycler_view"
android:layout_width="match_parent"
android:layout_height="250dp"
android:divider="#467FD7"
android:dividerHeight="10dp"
tools:listitem="@layout/recycler_view_check_in_contacts_list" />
</LinearLayout>
</FrameLayout>
以下是 tablayout 中第一个片段 (CheckInNewRecipients) 的 java 代码。
/**
* A simple {@link Fragment} subclass.
* Activities that contain this fragment must implement the
* {@link CheckInNewRecipients.OnFragmentInteractionListener} interface
* to handle interaction events.
* Use the {@link CheckInNewRecipients#newInstance} factory method to
* create an instance of this fragment.
*/
public class CheckInNewRecipients extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
public CheckInNewRecipients() {
// Required empty public constructor
Log.i(TAG, "CheckInNewRecipients: ");
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment CheckInNewRecipients.
*/
// TODO: Rename and change types and number of parameters
public static CheckInNewRecipients newInstance(String param1, String param2) {
CheckInNewRecipients fragment = new CheckInNewRecipients();
Log.i(TAG, "CheckInNewRecipients newInstance: ");
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i(TAG, "CheckInNewRecipients onCreate: ");
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.i(TAG, "CheckInNewRecipients onCreateView: ");
// Inflate the layout for this fragment
ContactsSelectionListDisplay contactsSelectionListDisplay = new
ContactsSelectionListDisplay(R.layout.activity_check_in_new, getActivity());
ContactsFilterAndDisplay contactsFilterAndDisplay =
new ContactsFilterAndDisplay(R.layout.activity_check_in_new, getActivity());
FragmentManager fm = getActivity().getSupportFragmentManager();
fm.beginTransaction().add(R.id.check_in_recipient_contacts_list_recycler_view,
contactsFilterAndDisplay).commit();
fm.beginTransaction().add(R.id.check_in_recipient_selection_list_recycler_view,
contactsSelectionListDisplay).commit();
return inflater.inflate(R.layout.fragment_check_in_new_recipients, container, false);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
Log.i(TAG, "CheckInNewRecipients onButtonPressed: ");
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.i(TAG, "CheckInNewRecipients onAttach: ");
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
以下是第一个子片段（ContactsSelectionListDisplay.java）的java代码
/**
* A simple {@link Fragment} subclass.
* Activities that contain this fragment must implement the
* {@link ContactsSelectionListDisplay.OnFragmentInteractionListener} interface
* to handle interaction events.
* Use the {@link ContactsSelectionListDisplay#newInstance} factory method to
* create an instance of this fragment.
*/
public class ContactsSelectionListDisplay extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private RecyclerView recyclerView;
private RecyclerView.Adapter checkInContactSelectionListAdapter;
//private RecyclerView.LayoutManager layoutManager;
private MainViewModel mViewModel;
private CheckInContactsSelectionListDisplayAdapter mAdapter;
private MainViewModelProviderFactory viewModelFactory;
private TextView checkInContactsPhotoThumbnail;
private TextView checkInContactsDisplayLastName;
private TextView checkInContactsDisplayFirstName;
private TextView checkInContactsListGroups;
private Context context;
private ContactsSelectionListDisplay.OnFragmentInteractionListener mListener;
public ContactsSelectionListDisplay(int layoutID, Context context) {
// Required empty public constructor
Log.i(TAG, "ContactsSelectionListDisplay: ");
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
//* @param param1 Parameter 1.
//* @param param2 Parameter 2.
* @return A new instance of fragment ContactsSelectionLIstDisplay.
*/
// TODO: Rename and change types and number of parameters
public static ContactsSelectionListDisplay newInstance(int layoutid, Context context) {
ContactsSelectionListDisplay fragment =
new ContactsSelectionListDisplay(R.layout.activity_check_in_new, context);
Bundle args = new Bundle();
//args.putString(ARG_PARAM1, param1);
//args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
Log.i(TAG, "ContactsSelectionListDisplay newInstance: ");
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i(TAG, "ContactsSelectionListDisplay onCreate: ");
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
viewModelFactory = new MainViewModelProviderFactory(this.context);
mViewModel = new ViewModelProvider(this, viewModelFactory).get(MainViewModel.class);
Log.i(TAG, "ContactsSelectionListDisplay onCreateView: ");
mAdapter = new CheckInContactsSelectionListDisplayAdapter(R.layout.fragment_contacts_selection_list_display, context);
RecyclerView recyclerView = getActivity().findViewById(R.id.check_in_recipient_selection_list_recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(mAdapter);
recyclerView.addItemDecoration(new DividerItemDecoration(getContext(),
LinearLayoutManager.VERTICAL));
return inflater.inflate(R.layout.fragment_contacts_selection_list_display, container, false);
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.i(TAG, "ContactsSelectionListDisplay : OnAttach");
viewModelFactory = new MainViewModelProviderFactory(context.getApplicationContext());
mViewModel = new ViewModelProvider(this, viewModelFactory).get(MainViewModel.class);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.i(TAG, "ContactsSelectionListDisplay: On Activity Created");
context = this.getContext();
mViewModel = new ViewModelProvider(this, viewModelFactory).get(MainViewModel.class);
mAdapter = new CheckInContactsSelectionListDisplayAdapter(R.layout.fragment_contacts_selection_list_display, context);
RecyclerView recyclerView = getView().findViewById(R.id.check_in_recipient_selection_list_recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
recyclerView.setAdapter(mAdapter);
recyclerView.addItemDecoration(new DividerItemDecoration(getContext(),
LinearLayoutManager.VERTICAL));
observerSetup();
Log.i(TAG, "ContactsSelectionListDisplay onActivityCreated: Observer SetUp");
ItemTouchHelper.SimpleCallback callback = new
ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT | ItemTouchHelper.LEFT) {
public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
return false;
}
@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
int position = viewHolder.getAdapterPosition();
mAdapter.deleteItem(position);
Snackbar snackbar = Snackbar.make(viewHolder.itemView, "Item " + (direction == ItemTouchHelper.RIGHT ? "deleted" : "archived") + ".", Snackbar.LENGTH_LONG);
snackbar.setDuration(3000);
snackbar.setAction(android.R.string.cancel, new View.OnClickListener() {
@Override
public void onClick(View view) {
mAdapter.undoDelete();
}
});
snackbar.show();
}
@Override
public void onChildDraw (Canvas c, RecyclerView
recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY,
int actionState, boolean isCurrentlyActive){
new RecyclerViewSwipeDecorator.Builder(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
.addSwipeLeftBackgroundColor(ContextCompat.getColor(getContext(), R.color.recycler_view_item_swipe_left_background))
.addSwipeLeftActionIcon(R.drawable.ic_archive_white_24dp)
.addSwipeRightBackgroundColor(ContextCompat.getColor(getContext(), R.color.recycler_view_item_swipe_right_background))
.addSwipeRightActionIcon(R.drawable.ic_delete_white_24dp)
.addSwipeRightLabel(getString(R.string.action_delete))
.setSwipeRightLabelColor(Color.WHITE)
.addSwipeLeftLabel(getString(R.string.action_archive))
.setSwipeLeftLabelColor(Color.WHITE)
.create()
.decorate();
super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
}
};
ItemTouchHelper itemTouchHelper = new ItemTouchHelper(callback);
itemTouchHelper.attachToRecyclerView(recyclerView);
CustomToast newtoast = new CustomToast(getContext(),"you clicked on this" );
newtoast.show();
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
private void observerSetup() {
Log.i(TAG, "ContactsSelectionListDisplay observerSetup:");
checkInContactsPhotoThumbnail = getView().findViewById(R.id.checkInRecipientSelectedPhotoThumbnail);
checkInContactsDisplayLastName = getView().findViewById(R.id.checkInRecipientSelectedLastName);
checkInContactsDisplayFirstName = getView().findViewById(R.id.checkInRecipientSelectedFirstName);
checkInContactsListGroups = getView().findViewById(R.id.checkInRecipientSelectedGroups);
if(mViewModel.getSelectionListContacts() != null)
Log.i(TAG, "ContactsSelectionListDisplay getSelectionListContacts != null observerSetup: ");
Objects.requireNonNull(mViewModel.getSelectionListContacts()).observe(getViewLifecycleOwner(),
new Observer<List<ContactTable>>() {
@Override
public void onChanged(@Nullable final List<ContactTable> allSelectionListContacts) {
Log.i(TAG, "ContactsSelectionListDisplay observer setup onChanged: ");
mAdapter.setContactList(allSelectionListContacts);
}
});
}
}
以下是第一个子片段的回收器适配器（ContactListSelectionAndDisplayAdapter）
public class CheckInContactsSelectionListDisplayAdapter extends
RecyclerView.Adapter<CheckInContactsSelectionListDisplayAdapter.ViewHolder> {
private int contactSelectionListLayout;
private List<ContactTable> contactSelectionList;
private List<ContactTable> foundContact;
private List<ContactTable> foundContactByContract;
private CoordinatorLayout coordinatorLayout;
private RecyclerView recyclerView;
private ContactTable mRecentlyDeletedItem;
private ContactTable mContactToDelete;
private ContactTableDao contactTableDao;
private ContactTableRepository contactTableRepository;
private int mContactTablePrimaryKey;
private int mContactPrimaryKey;
private int mCheckInRecipientsTablePrimaryKey;
private String mContactLastName;
private int mRecentlyDeletedItemPosition;
private Context context;
private MainViewModel mViewModel;
private MainViewModelProviderFactory viewModelFactory;
//private ArrayList recipientsToDelete = new ArrayList(20);
private int indexPosition;
private int index;
private int numberOfRecipientsToDelete;
private List<Integer> tableOfContactsToDelete;
private List<Integer> contactsToDelete;
private List<ContactTable> contactsToInsert ;
private ContactTable mContactsTableRecord;
private MyFirebaseMessagingService myFirebaseMessagingService;
public CheckInContactsSelectionListDisplayAdapter(int layoutId, Context context) {
Log.i(TAG, "CheckInContactsSelectionListDisplayAdapter: ");
contactSelectionListLayout = layoutId;
this.context = context;
}
public void setContactList(List<ContactTable> allSelectionListContacts) {
contactSelectionList = allSelectionListContacts;
Log.i(TAG, "ContactsSelectionListDisplayAdapter setContactList: ");
notifyDataSetChanged();
}
public void deleteItem(int position) {
Log.i(TAG, "ContactsSelectionListDisplayAdapter deleteItem: ");
indexPosition = 0;
mRecentlyDeletedItem = contactSelectionList.get(position);
mRecentlyDeletedItemPosition = position;
mContactTablePrimaryKey = contactSelectionList.get(position).getContactTablePrimaryKey();
mContactPrimaryKey = mContactTablePrimaryKey;
mContactLastName = contactSelectionList.get(position).getContactLastName();
viewModelFactory = new MainViewModelProviderFactory(context.getApplicationContext());
mViewModel = new MainViewModel(context.getApplicationContext());
contactSelectionList.remove(position);
notifyItemRemoved(position);
}
public void undoDelete() {
Log.i(TAG, "ContactsSelectionListDisplayAdapter undoDelete: ");
contactSelectionList.add(mRecentlyDeletedItemPosition,
mRecentlyDeletedItem);
notifyItemInserted(mRecentlyDeletedItemPosition);
//reinsert of record from Contact delete
mViewModel.insertContact(mRecentlyDeletedItem);
//reinsert CheckInRecipientsTable records from CheckIn associated delete
//undoDeleteRecipientsForCheckIn();
}
@Override
public int getItemCount() {
Log.i(TAG, "ContactsSelectionListDisplayAdapter getItemCount: ");
if (contactSelectionList == null)
return 0;
else
return contactSelectionList.size();
//return contactSelectionList == null ? 0 : contactSelectionList.size();
}
@Override
public CheckInContactsSelectionListDisplayAdapter.ViewHolder
onCreateViewHolder(ViewGroup parent, int viewType) {
Log.i(TAG, "ContactsSelectionListDisplayAdapter onCreateViewHolder: ");
View view = LayoutInflater.from(
parent.getContext()).inflate(R.layout.recycler_view_check_in_contacts_list, parent, false);
CheckInContactsSelectionListDisplayAdapter.ViewHolder checkInContactListViewHolder = new CheckInContactsSelectionListDisplayAdapter.ViewHolder(view);
return checkInContactListViewHolder;
}
@Override
public void onBindViewHolder(final CheckInContactsSelectionListDisplayAdapter.ViewHolder holder, final int listPosition) {
TextView contactTablePrimaryKey = holder.contactTablePrimaryKey;
TextView contactLastName = holder.contactLastName;
TextView contactFirstName = holder.contactFirstName;
Log.i(TAG, "ContactsSelectionListDisplayAdapter onBindViewHolder: ");
contactTablePrimaryKey.setText(contactSelectionList.get(listPosition).getContactTablePrimaryKey());
contactLastName.setText(contactSelectionList.get(listPosition).getContactLastName());
contactFirstName.setText(contactSelectionList.get(listPosition).getContactFirstName());
}
static class ViewHolder extends RecyclerView.ViewHolder {
TextView contactTablePrimaryKey;
TextView contactLastName;
TextView contactFirstName;
TextView contactThumbnailPhoto;
TextView contactGroupsList;
Button contactSelectedButton;
ViewHolder(View itemView) {
super(itemView);
Log.i(TAG, "ContactsSelectionListDisplayAdapter ViewHolder: ");
contactTablePrimaryKey = itemView.findViewById(R.id.checkInTablePrimaryKey);
contactLastName = itemView.findViewById(R.id.checkInContactsDisplayLastName);
contactFirstName = itemView.findViewById(R.id.checkInContactsDisplayFirstName);
contactThumbnailPhoto = itemView.findViewById(R.id.checkInContactsListPhotoThumbnail);
}
}
}
解决方案
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