Question

我有2个收藏集；预订信息和停车区。从ParkingArea文档中，我想将“ areanumber”字段的最新值保存到具有字段名称“ Area”的BookingInformation集合中。

我尝试了以下方法。在logcat中，我可以查看所需的数据，但不知道如何分配它们。我没有找到任何资源。请帮忙。

final List<String> parkingDocList = new ArrayList<>();

dataStore.collection("ParkingArea").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            for (QueryDocumentSnapshot documentSnapshot : task.getResult()) {
                parkingDocList.add(documentSnapshot.getId());
            }
        } 
    }
});

final Map<String, Object> reserveInfo = new HashMap<>();

reserveInfo.put("date", date.getText().toString());
reserveInfo.put("startTime", startTime.getText().toString());
reserveInfo.put("endTime", endTime.getText().toString());
reserveInfo.put("userId", currentUserId);
reserveInfo.put("area", allocatedArea[0]);

dataStore.collection("BookingInformation").document(id).set(reserveInfo)
    .addOnCompleteListener(new OnCompleteListener<Void>() {
        @Override
        public void onComplete(@NonNull Task<Void> task) {
            Toast toast4 =
                    Toast.makeText(getActivity().getApplicationContext(),
                            "Area reserved successfully", Toast.LENGTH_SHORT);
            toast4.show();
        }
    })
    .addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Toast toast5 = Toast.makeText(getActivity().getApplicationContext(), "Reservation failed", Toast.LENGTH_SHORT);
            toast5.show();
        }
    });

Answer 1

从Firestore（和大多数云API）异步加载数据。这意味着需要从数据库中获取数据的任何代码都必须在内部内，onComplete处理程序在加载数据时被调用。

所以在您的情况下：

final List<String> parkingDocList = new ArrayList<>();

dataStore.collection("ParkingArea").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        if (task.isSuccessful()) {
            for (QueryDocumentSnapshot documentSnapshot : task.getResult()) {
                parkingDocList.add(documentSnapshot.getId());
            }

            final Map<String, Object> reserveInfo = new HashMap<>();

            reserveInfo.put("date", date.getText().toString());
            reserveInfo.put("startTime", startTime.getText().toString());
            reserveInfo.put("endTime", endTime.getText().toString());
            reserveInfo.put("userId", currentUserId);
            reserveInfo.put("area", allocatedArea[0]);

            dataStore.collection("BookingInformation").document(id).set(reserveInfo)
                .addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        Toast toast4 =
                                Toast.makeText(getActivity().getApplicationContext(),
                                        "Area reserved successfully", Toast.LENGTH_SHORT);
                        toast4.show();
                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Toast toast5 = Toast.makeText(getActivity().getApplicationContext(), "Reservation failed", Toast.LENGTH_SHORT);
                        toast5.show();
                    }
                });
        } 
    }
});

如何使用Java将集合文档的字段值作为Firestore中的值分配给另一个集合文档字段？

1 个答案: