為什么 Firestore 數據庫中的數據在 FirestoreRecyclerAdapter 中返回為“null”？

Question

在從 Firestore 寫入和讀取數據成功后，我現在嘗試使用 FirestoreRecyclerAdapter 在RecyclerView中顯示該數據。 但是，在我的onBindViewHolder中，我嘗試使用數據庫中的數據設置 textView，我得到了 NullPointerException，其中我的客戶端名稱是 null。

這是我的 FirestoreAdapter class：

public class FirestoreAdapter extends FirestoreRecyclerAdapter<ServiceOrder, FirestoreAdapter.ViewHolder> {

    public FirestoreAdapter(@NonNull FirestoreRecyclerOptions<ServiceOrder> options) {
        super(options);
    }

    @Override
    protected void onBindViewHolder(@NonNull ViewHolder holder, int position, @NonNull ServiceOrder model) {
        holder.osIdItem.setText(String.valueOf(getItem(position).getId()));
        holder.osClientItem.setText(getItem(position).getClient().getName()); //Line with error
        holder.osDateItem.setText(getItem(position).getDate());
        holder.osValueItem.setText(String.valueOf(getItem(position).getTotalValue()));
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());

        View view = layoutInflater.inflate(R.layout.layout_os_item, parent, false);

        return new FirestoreAdapter.ViewHolder(view);
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        private  TextView osIdItem;
        private  TextView osClientItem;
        private  TextView osDateItem;
        private  TextView osValueItem;

        public ViewHolder(View itemView) {
            super(itemView);

            osIdItem =  itemView.findViewById(R.id.osIDItem);
            osClientItem =   itemView.findViewById(R.id.osClientNameItem);
            osDateItem =  itemView.findViewById(R.id.osDateItem);
            osValueItem =  itemView.findViewById(R.id.osValueItem);
        }
    }
}

這是我的 Logcat

 2022-09-09 09:58:38.479 1147-1147/com.leonardomaito.autocommobile E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.leonardomaito.autocommobile, PID: 1147
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.leonardomaito.autocommobile.models.Client.getName()' on a null object reference
        at com.leonardomaito.autocommobile.adapters.FirestoreAdapter.onBindViewHolder(FirestoreAdapter.java:27)
        at com.leonardomaito.autocommobile.adapters.FirestoreAdapter.onBindViewHolder(FirestoreAdapter.java:18)
        at com.firebase.ui.firestore.FirestoreRecyclerAdapter.onBindViewHolder(FirestoreRecyclerAdapter.java:157)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7254)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7337)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6194)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6460)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6300)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6296)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2330)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1631)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1591)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:668)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4309)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:4012)
        at androidx.recyclerview.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:2028)
        at androidx.recyclerview.widget.RecyclerView$1.run(RecyclerView.java:417)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
        at android.view.Choreographer.doCallbacks(Choreographer.java:723)
        at android.view.Choreographer.doFrame(Choreographer.java:655)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
        at android.os.Handler.handleCallback(Handler.java:789)
        at android.os.Handler.dispatchMessage(Handler.java:98)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

我的Client class 正在使用 Builder 設計模式，以及 Firestore 所需的默認構造函數，以及用於通過活動傳輸數據的 Parcelable，我只是添加它，因為我不確定它是否會影響 Firestore 讀取我的方式數據。

那么，為什么我可以使用讀寫數據到數據庫，但我似乎無法顯示呢？ 我的數據庫中有一個Client “名稱”，它不應該顯示嗎？

如果有幫助，我的ServiceOrder class 需要Vehicle和Client object 才能構建。

這就是我的數據在 Firestore 中的結構方式：

第1部分

第2部分

謝謝你。

編輯

根據要求，Firestore 參考：

public class OsActivity extends AppCompatActivity {

    private FirestoreAdapter listAdapter;
    private FirebaseFirestore db = FirebaseFirestore.getInstance();
    private CollectionReference osRef = db.collection("cliente");

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_os);


        setupRecyclerView();

        }

        private void setupRecyclerView() {

            RecyclerView recyclerView = findViewById(R.id.recyclerViewOs);

            Query query = osRef.orderBy("ServiceOrder",
                    Query.Direction.ASCENDING);

            FirestoreRecyclerOptions<ServiceOrder> options =
                    new FirestoreRecyclerOptions.Builder<ServiceOrder>()
                            .setQuery(query, ServiceOrder.class)
                            .build();

            listAdapter = new FirestoreAdapter(options);


            recyclerView.setHasFixedSize(true);
            recyclerView.setLayoutManager(new LinearLayoutManager(this));
            recyclerView.setAdapter(listAdapter);
        }

    @Override
    protected void onStart() {
        super.onStart();
        listAdapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        listAdapter.stopListening();
    }

運行另一個調試器並收到以下消息No setter/field for ServiceOrder found on class com.leonardomaito.autocommobile.models.ServiceOrder

數據庫模式

Firebase 控制台

服務訂單 Class

public class ServiceOrder {

    public Client client;
    public Vehicle vehicle;
    private String service;
    private String observation;
    private String paymentForm;
    private String date;
    private double totalValue;
    private int id;

    public ServiceOrder() {
    }

    private ServiceOrder(ServiceOrderBuilder serviceOrderBuilder){
        this.client = serviceOrderBuilder.client;
        this.vehicle = serviceOrderBuilder.vehicle;
        this.service = serviceOrderBuilder.service;
        this.paymentForm = serviceOrderBuilder.paymentForm;
        this.observation = serviceOrderBuilder.observation;
        this.totalValue = serviceOrderBuilder.value;
        this.date = serviceOrderBuilder.date;

    }



    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public double getTotalValue() {
        return totalValue;
    }

    public void setTotalValue(double totalValue) {
        this.totalValue = totalValue;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

   public Client getClient() {
        return client;
    }

    public void setClient(Client client) {
        this.client = client;
    }

    public Vehicle getVehicle() {
        return vehicle;
    }

    public void setVehicle(Vehicle vehicle) {
        this.vehicle = vehicle;
    }

    public String getService() {
        return service;
    }

    public void setService(String service) {
        this.service = service;
    }

    public String getObservation() {
        return observation;
    }

    public void setObservation(String observation) {
        this.observation = observation;
    }

    public String getPaymentForm() {
        return paymentForm;
    }

    public void setPaymentForm(String paymentForm) {
        this.paymentForm = paymentForm;
    }

    public static class ServiceOrderBuilder {

        private Vehicle vehicle;
        private Client client;
        private final String service;
        private final String paymentForm;
        private final int id;
        private final double value;
        private final String date;
        private String observation;

        public ServiceOrderBuilder(Client client, Vehicle vehicle,
                                   String service, String paymentForm,
                                   int id, double value, String date) {
            this.client = client;
            this.vehicle = vehicle;
            this.service = service;
            this.paymentForm = paymentForm;
            this.id = id;
            this.value = value;
            this.date = date;
        }

        public ServiceOrder.ServiceOrderBuilder observation(String observation) {
            this.observation = observation;
            return this;
        }

        public ServiceOrder build() {
            ServiceOrder serviceOrder = new ServiceOrder(this);
            return serviceOrder;

        }
    }
}

Answer 1

由於您使用的是 Firebase-UI 庫，因此當您使用以下方法調用時：

.setQuery(query, ServiceOrder.class)

這意味着您正在嘗試將查詢返回的所有文檔 map 轉換為ServiceOrder類型的對象。 但這實際上是不可能的，因為您的實際文檔如下所示：

clienteTeste (document)
  |
  --- ServiceOrder (map)
        |
        --- client: {...} (map)
        |
        --- date: "09/09/2022"
        |
        --- //other fields

而不是這個：

clienteTeste (document)
  |
  --- client: {...} (map)
  |
  --- date: "09/09/2022"
  |
  --- //other fields

看，沒有ServiceOrder額外的object？ 這將是解決此問題的最簡單解決方案，其中字段應直接添加到文檔中，而不是map 內。

但是，如果您無法更改文檔結構，我對此表示懷疑，因為那里只有一個（測試）文檔，那么您應該考慮通過創建另一個 class 來使用封裝，其中包含一個名為ServiceOrder的單個字段，該字段的類型應該是ServiceOrder 。 然后將map的每一個文件變成一個object這個新的class。