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社区首页 >问答首页 >ConstraintLayout没有在RecyclerView上单击项的NavController设置

问ConstraintLayout没有在RecyclerView上单击项的NavController设置
EN

Stack Overflow用户
提问于 2020-04-01 02:00:01
回答 3查看 9.7K关注 0票数 4

当我点击一个项目时，它有时会工作，有时会崩溃。

下面是单击某项后的致命异常。

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2020-03-31 21:59:18.087 15383-15383/com.aliton.myapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.aliton.myapp, PID: 15383
    java.lang.IllegalStateException: View androidx.constraintlayout.widget.ConstraintLayout{b3bb13b V.E...C.. .......D 0,336-720,518} does not have a NavController set
        at androidx.navigation.Navigation.findNavController(Navigation.java:84)
        at com.aliton.myapp.Adapter.StoreSelectAdapter$StoreSelectViewHolder$1.onChanged(StoreSelectAdapter.java:147)
        at com.aliton.myapp.Adapter.StoreSelectAdapter$StoreSelectViewHolder$1.onChanged(StoreSelectAdapter.java:142)
        at androidx.lifecycle.LiveData.considerNotify(LiveData.java:131)
        at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:149)
        at androidx.lifecycle.LiveData.setValue(LiveData.java:307)
        at androidx.lifecycle.MutableLiveData.setValue(MutableLiveData.java:50)
        at androidx.lifecycle.LiveData$1.run(LiveData.java:91)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6351)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:896)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:786)

在这种情况下，首先我需要将一个项目(StoreEntity)插入到我的房间数据库中，侦听它的id，然后导航到带有在direction中定义的对象的其他片段。

下面是我的适配器：

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public class StoreSelectAdapter extends RecyclerView.Adapter<StoreSelectAdapter.StoreSelectViewHolder> {

    private static final String TAG = "debinf SummaryAdapter";

    private FragmentActivity fragmentActivity;

    public StoreSelectAdapter(FragmentActivity fragmentActivity) {
        this.fragmentActivity = fragmentActivity;
    }

    private static final DiffUtil.ItemCallback<StoreModel> DIFF_CALLBACK = new DiffUtil.ItemCallback<StoreModel>() {
        @Override
        public boolean areItemsTheSame(@NonNull StoreModel oldItem, @NonNull StoreModel newItem) {
            return oldItem.getKey().equals(newItem.getKey());
        }

        @Override
        public boolean areContentsTheSame(@NonNull StoreModel oldItem, @NonNull StoreModel newItem) {
            return oldItem.getKey().equals(newItem.getKey()) && oldItem.getName().equals(newItem.getName()) && oldItem.getAddress().equals(newItem.getAddress());
        }
    };

    private AsyncListDiffer<StoreModel> differ = new AsyncListDiffer<StoreModel>(this, DIFF_CALLBACK);

    @NonNull
    @Override
    public StoreSelectViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_select_store, parent, false);
        return new StoreSelectViewHolder(view, fragmentActivity);
    }

    @Override
    public void onBindViewHolder(@NonNull StoreSelectViewHolder holder, int position) {
        StoreModel store = differ.getCurrentList().get(position);
        Log.i(TAG, "onBindViewHolder: "+store.getName());

        holder.storeName.setText(store.getName());
        holder.storeAddress.setText(store.getAddress());

        if (store.getImage() != null && !store.getImage().isEmpty()) {
            Picasso.get().load(store.getImage()).networkPolicy(NetworkPolicy.OFFLINE).into(holder.storeImage, new Callback() {
                @Override
                public void onSuccess() {

                }

                @Override
                public void onError(Exception e) {
                    Picasso.get().load(store.getImage()).into(holder.storeImage);
                }
            });
        } else {
            holder.storeImage.setImageResource(android.R.drawable.stat_sys_phone_call_on_hold);
        }

        /*holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Log.i(TAG, "onClick: onBindViewHolder");
                Toast.makeText(context, "onClick: onBindViewHolder", Toast.LENGTH_SHORT).show();
                AddstoreFragmentDirections.ActionAddstoreFragmentToBarcodeFragment direction = AddstoreFragmentDirections.actionAddstoreFragmentToBarcodeFragment(store);
                Navigation.createNavigateOnClickListener()
            }
        });*/
    }

    @Override
    public int getItemCount() {
        return differ.getCurrentList().size();
    }

    public void submitList(List<StoreModel> stores) {
        differ.submitList(stores);
    }

    public List<StoreModel> getCurrentItemList() {
        return differ.getCurrentList();
    }

    public class StoreSelectViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        //private static final String TAG = "StoreSelectViewHolder";

        public ImageView storeImage;
        public TextView storeName, storeAddress;

        private FragmentActivity fragmentActivity;
        private LocalDatabaseViewModel localDatabaseViewModel;

        public StoreSelectViewHolder(@NonNull View itemView, FragmentActivity fragmentActivity) {
            super(itemView);

            storeImage = (ImageView) itemView.findViewById(R.id.item_store_image);
            storeName = (TextView) itemView.findViewById(R.id.item_store_name);
            storeAddress = (TextView) itemView.findViewById(R.id.item_store_address);

            this.fragmentActivity = fragmentActivity;

            itemView.setOnClickListener(this);

        }

        @Override
        public void onClick(View v) {
            StoreModel store = differ.getCurrentList().get(getAdapterPosition());
            Log.i(TAG, "onClick: storeName selected: "+store.getName());
            Log.i(TAG, "onClick: storeKey selected: "+store.getKey());
            StoreEntity storeEntity = new StoreEntity(store.getName(), store.getImage());
            storeEntity.setKey(store.getKey());
            localDatabaseViewModel = ViewModelProviders.of(fragmentActivity).get(LocalDatabaseViewModel.class);
            localDatabaseViewModel.getStoreIdFromInsertedItem().observe(fragmentActivity, new Observer<Long>() {
                @Override
                public void onChanged(Long itemId) {
                    Log.i(TAG, "onChanged: itemId in adapter is "+itemId);
                    SelectstoreFragmentDirections.ActionSelectstoreFragmentToBarcodeFragment direction = SelectstoreFragmentDirections.actionSelectstoreFragmentToBarcodeFragment(store, itemId); 
                    Navigation.findNavController(v).navigate(direction); // this is the StoreSelectAdapter.java:147
                }
            });
            localDatabaseViewModel.insertStore(storeEntity);


        }

    }
}

我很感谢为解决这个问题提供的任何帮助。

编辑

下面是我的activity_main.xml，其中声明了我的片段NavHost。

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<androidx.drawerlayout.widget.DrawerLayout
    android:id="@+id/main_drawer"
    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="match_parent"
    tools:context=".MainActivity">


    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <fragment
            android:id="@+id/main_fragment"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:name="androidx.navigation.fragment.NavHostFragment"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toTopOf="@id/main_bottomnav"
            app:defaultNavHost="true"
            app:navGraph="@navigation/mainnav_graph"/>

        <com.google.android.material.bottomnavigation.BottomNavigationView
            android:id="@+id/main_bottomnav"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:menu="@menu/main_navmenu"
            android:background="@color/colorAccent"
            app:itemIconTint="@drawable/botton_item_color"
            app:itemTextColor="@drawable/botton_item_color">

        </com.google.android.material.bottomnavigation.BottomNavigationView>

    </androidx.constraintlayout.widget.ConstraintLayout>

    <com.google.android.material.navigation.NavigationView
        android:id="@+id/main_sidebar"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/main_sidebarmenu"/>

</androidx.drawerlayout.widget.DrawerLayout>

下面是我的mainnav_graph.xml

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...
<fragment
    android:id="@+id/barcodeFragment"
    android:name="com.aliton.myapp.BarcodeFragment"
    android:label="fragment_barcode"
    tools:layout="@layout/fragment_barcode" >

    <argument
        android:name="store"
        app:argType="com.aliton.myapp.Model.StoreModel" />
    <action
        android:id="@+id/action_barcodeFragment_to_productdetailFragment"
        app:destination="@id/productdetailFragment" />
    <argument
        android:name="storeId"
        app:argType="long" />
</fragment>
<fragment
    android:id="@+id/selectstoreFragment"
    android:name="com.aliton.myapp.SelectstoreFragment"
    android:label="fragment_selectstore"
    tools:layout="@layout/fragment_selectstore" >
    <action
        android:id="@+id/action_selectstoreFragment_to_addstoreFragment"
        app:destination="@id/addstoreFragment" />
    <action
        android:id="@+id/action_selectstoreFragment_to_barcodeFragment"
        app:destination="@id/barcodeFragment" />
</fragment>
...

下面是我的fragment_selectstore.xml作为SelectstoreFragment.java的内容。

代码语言：javascript
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<androidx.constraintlayout.widget.ConstraintLayout
    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="match_parent"
    tools:context=".SelectstoreFragment">

    <androidx.cardview.widget.CardView
        android:id="@+id/selectstore_cardview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="8dp"
        app:cardCornerRadius="10dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent">

        <TextView
            android:id="@+id/selectstore_question"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Are you at any of the store shown below?"
            android:textSize="28sp"
            android:gravity="center"
            android:textStyle="bold"/>


    </androidx.cardview.widget.CardView>

    <FrameLayout
        android:id="@+id/selectstore_framelayout"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginTop="2dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/selectstore_cardview">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/selectstore_recyclerview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scrollbars="vertical">

        </androidx.recyclerview.widget.RecyclerView>

        <TextView
            android:id="@+id/selectstore_nodata"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:gravity="center"
            android:text="No store found!"
            android:textSize="22sp" />

    </FrameLayout>

    <com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton
        android:id="@+id/selectstore_fab"
        style="@style/Widget.MaterialComponents.ExtendedFloatingActionButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="8dp"
        android:contentDescription="Outra loja desc"
        android:text="Outra loja"
        app:icon="@drawable/common_full_open_on_phone"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

更新

1)我还实现了一个interface，用于Adapter和Fragment之间的通信，以便在onViewCreated()中获取view，但是应用程序不断崩溃。

2)我还尝试使用以下命令在片段布局中定义我的navController的NavHostFragment

代码语言：javascript
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@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    Log.i(TAG, "onViewCreated: ");

    // https://stackoverflow.com/a/53902696/4300670
    // NOT WORKING
    adapter = new StoreSelectAdapter(getActivity(), new StoreSelectAdapter.OnStoreSelectListener() {
        @Override
        public void onStoreSelected(StoreModel storeModel, Long itemId) {
            SelectstoreFragmentDirections.ActionSelectstoreFragmentToBarcodeFragment direction = SelectstoreFragmentDirections.actionSelectstoreFragmentToBarcodeFragment(storeModel, itemId);
            Navigation.findNavController(getActivity(), R.id.main_fragment).navigate(direction);
        }
    });
    storeRecyclerview.setAdapter(adapter);
}

但现在我得到了NullPointerException

代码语言：javascript
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2020-04-02 17:11:22.163 6015-6015/com.aliton.myapp E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.aliton.myapp, PID: 6015
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.app.Activity.requireViewById(int)' on a null object reference
        at androidx.core.app.ActivityCompat.requireViewById(ActivityCompat.java:363)
        at androidx.navigation.Navigation.findNavController(Navigation.java:58)
        at com.aliton.myapp.SelectstoreFragment$4.onStoreSelected(SelectstoreFragment.java:221)
        at com.aliton.myapp.Adapter.StoreSelectAdapter$StoreSelectViewHolder$1.onChanged(StoreSelectAdapter.java:149)
        at com.aliton.myapp.Adapter.StoreSelectAdapter$StoreSelectViewHolder$1.onChanged(StoreSelectAdapter.java:145)
        at androidx.lifecycle.LiveData.considerNotify(LiveData.java:131)
        at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:149)
        at androidx.lifecycle.LiveData.setValue(LiveData.java:307)
        at androidx.lifecycle.MutableLiveData.setValue(MutableLiveData.java:50)
        at androidx.lifecycle.LiveData$1.run(LiveData.java:91)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

3)为了了解导致错误的原因，我在Navigation类中复制了这些方法，如下所示：

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@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    Log.i(TAG, "onViewCreated: ");

    adapter = new StoreSelectAdapter(getActivity(), new StoreSelectAdapter.OnStoreSelectListener() {
        @Override
        public void onStoreSelected(StoreModel storeModel, Long itemId) {
            SelectstoreFragmentDirections.ActionSelectstoreFragmentToBarcodeFragment direction = SelectstoreFragmentDirections.actionSelectstoreFragmentToBarcodeFragment(storeModel, itemId);
            NavController navController = myFindViewNavController(view);
            if (navController == null) {
                Log.i(TAG, "onStoreSelected: ISSUE NavController set");
            }                

        }
    });

    storeRecyclerview.setAdapter(adapter);
}

private NavController myFindViewNavController(View view) {
    while (view != null) {
        Log.i(TAG, "myFindViewNavController: view != null - "+view);
        NavController controller = myGetViewNavController(view);
        if (controller != null) {
            Log.i(TAG, "myFindViewNavController: controller != null");
            return controller;
        }
        ViewParent parent = view.getParent();
        view = parent instanceof View ? (View) parent : null;
        Log.i(TAG, "myFindViewNavController: view.getParent() - "+view);
    }
    return null;
}

private NavController myGetViewNavController(View view) {
    Object tag = view.getTag(R.id.nav_controller_view_tag);
    Log.i(TAG, "myGetViewNavController: tag is "+tag);
    NavController controller = null;
    if (tag instanceof WeakReference) {
        Log.i(TAG, "myGetViewNavController: tag instanceof WeakReference");
        controller = ((WeakReference<NavController>) tag).get();
    } else if (tag instanceof NavController) {
        Log.i(TAG, "myGetViewNavController: tag instanceof NavController");
        controller = (NavController) tag;
    }
    return controller;
}

验证logcat之后，在导航到下一个片段之后，似乎再次触发了Myadapter中的adapter：

代码语言：javascript
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debinf SummaryAdapter: onClick: storeName selected: Posto Shell Convem
debinf SummaryAdapter: onClick: storeKey selected: M0Ysk5jRIdtiJ9zyUhXG
debinf SummaryAdapter: onChanged: itemId in adapter is 40, view id: -1
debinf SelStoreFrag: myFindViewNavController: view != null - androidx.constraintlayout.widget.ConstraintLayout{fb9835d V.E...... ........ 0,0-1080,1437}
debinf SelStoreFrag: myGetViewNavController: tag is null
debinf SelStoreFrag: myFindViewNavController: view.getParent() - android.widget.FrameLayout{4af5206 V.E...... ........ 0,0-1080,1437 #7f090137 app:id/main_fragment}
debinf SelStoreFrag: myFindViewNavController: view != null - android.widget.FrameLayout{4af5206 V.E...... ........ 0,0-1080,1437 #7f090137 app:id/main_fragment}
debinf SelStoreFrag: myGetViewNavController: tag is androidx.navigation.NavController@47f0c7
debinf SelStoreFrag: myGetViewNavController: tag instanceof NavController
debinf SelStoreFrag: myFindViewNavController: controller != null
debinf BarcodeFrag: onCreateView: 
debinf BarcodeFrag: onCreateView: fragArgs is com.aliton.myapp.Model.StoreModel@77fbfcb
debinf BarcodeFrag: onPermissionGranted: 
debinf BarcodeFrag: startCamera: 
debinf ExtFun: isFlashSupported: false
debinf ExtFun: startCameraForAllDevices: 
debinf BarcodeFrag: onResume:
debinf SummaryAdapter: onChanged: itemId in adapter is 41, view id: -1
debinf SelStoreFrag: myFindViewNavController: view != null - androidx.constraintlayout.widget.ConstraintLayout{fb9835d V.E...... .......D 0,0-1080,1437}
debinf SelStoreFrag: myGetViewNavController: tag is null
debinf SelStoreFrag: myFindViewNavController: view.getParent() - null
debinf SelStoreFrag: onStoreSelected: ISSUE NavController set

解决方案似乎是通过在id中通过ViewModel正确地解决插入项adapter的侦听问题来实现的。

android-recyclerview
navigation
android
EN

回答 3

Stack Overflow用户

回答已采纳

发布于 2020-04-06 18:48:33

IllegalStateException或NullPointerException不再发生，因为我已经从adapter中删除了ViewModel并将其放置在fragment中。

代码语言：javascript
运行
复制
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    Log.i(TAG, "onViewCreated: ");

    localDatabaseViewModel = ViewModelProviders.of(getActivity()).get(LocalDatabaseViewModel.class);
    adapter = new StoreSelectAdapter(new StoreSelectAdapter.OnStoreSelectListener() {
        @Override
        public void onStoreSelected(StoreModel storeModel) {
            StoreEntity storeEntity = new StoreEntity(storeModel.getName(), storeModel.getImage());
            storeEntity.setKey(storeModel.getKey());
            localDatabaseViewModel.getStoreIdFromInsertedItem().observe(getViewLifecycleOwner(), new Observer<Long>() {
                @Override
                public void onChanged(Long itemId) {
                    SelectstoreFragmentDirections.ActionSelectstoreFragmentToBarcodeFragment direction = SelectstoreFragmentDirections.actionSelectstoreFragmentToBarcodeFragment(storeModel, itemId);
                    Navigation.findNavController(view).navigate(direction);
                }
            });
            localDatabaseViewModel.insertStore(storeEntity);

        }
    });

    storeRecyclerview.setAdapter(adapter);
}

停止监听房间数据库中插入项的id。

代码语言：javascript
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@Override
public void onStop() {
    Log.i(TAG, "onStop: ");
    if (localDatabaseViewModel != null) {
        localDatabaseViewModel.getStoreIdFromInsertedItem().removeObservers(getViewLifecycleOwner());
    }
    super.onStop();
}
票数 0
EN

Stack Overflow用户

发布于 2020-07-19 08:03:43

对于适配器的绑定方法，我遇到了一些类似的问题，对我起作用的是更改这一行。

代码语言：javascript
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复制
navController = Navigation.findNavController(itemView)

至

代码语言：javascript
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navController = Navigation.findNavController(activity, R.id.nav_host_fragment)
票数 7
EN

Stack Overflow用户

发布于 2020-04-03 22:21:43

在将接口实现移动到片段.之前，使用

您正在从错误的位置或使用错误的访问权限访问NavController。

您必须将此操作移动到承载回收器视图的片段中。然后你可以导航到你想要的目的地。

代码语言：javascript
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findNavController().navigate(R.id.your_destination)

将接口实现移动到片段.之后的

通过错误的访问器访问NavController，只需调用findNavController()方法即可。

对于摘要，可以初始化适配器。

代码语言：javascript
运行
复制
adapter = new StoreSelectAdapter(getActivity(), new StoreSelectAdapter.OnStoreSelectListener() {
        @Override
        public void onStoreSelected(StoreModel storeModel, Long itemId) {
            SelectstoreFragmentDirections.ActionSelectstoreFragmentToBarcodeFragment direction = SelectstoreFragmentDirections.actionSelectstoreFragmentToBarcodeFragment(storeModel, itemId);
            findNavController().navigate(direction);
        }
    });

findNavController()函数/方法是在包androidx.navigation.fragment下找到的片段的扩展函数。

希望你能明白我想要说明的。

票数 1
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/60962539

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