Question

每次活动开始时，Firebase文档字段都会重置，我需要保留它们。

集合和文档的创建是在onResume中使用“ setOptions.merge（）”完成的，对于String，将文档值设置为null；对于数组，将文档值设置为emptyList。

    @Override
    protected void onResume() {
        super.onResume();

        //Creating the document if it does not already exist.

        Map<String, Object> read_book = new HashMap<>();
        read_book.put("read_pages", Collections.emptyList());
        read_book.put("total_pages", null);

        fireStoreDB.collection("user_" + user.getId).document("book_" + book.getId())
                .set(read_book, SetOptions.merge())
                .addOnSuccessListener(aVoid ->
                        Log.d("Activity", "FirestoreDB => created empty read_pages and total_pages"))
                .addOnFailureListener(e ->
                        Log.d("Activity", "Firestore failed to create empty read_pages and total_pages" + e));
    }

private void pageFlip(String currentPage, String totalPages){

        // Add read page to array (no duplicates)

        fireStoreDB.collection("user_" + user.getId).document("book_" + book.getId())
                .update("read_pages", FieldValue.arrayUnion(currentPage))
                .addOnSuccessListener(aVoid ->
                        Log.d("Activity", "FirestoreDB => updated read_pages " + currentPage))
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.d("Activity", "FirestoreDB => failed to update read_pages" + e);
                    }
                });

        // Set total book pages number

        fireStoreDB.collection("user_" + user.getId).document("book_" + book.getId())
                .update("total_pages", totalPages)
                .addOnSuccessListener(aVoid ->
                        Log.d("Activity", "FirestoreDB => updated total_pages " + totalPages))
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.d("Activity", "FirestoreDB => failed to update total_pages" + e);
                    }
                });
}

使用上述代码，每次调用onResume时，该字段都将重置为null和空列表。

我需要total_pages值和read_pages数组才能在Activity重新启动时持续存在，并且可以使用FieldValue.arrayUnion向read_pages数组添加新值。

实现用例的有效方法是什么？

Answer 1

您可以直接将Set方法与SetOptions.merge（）一起使用，而无需使用空值初始化

private void pageFlip(String currentPage, String totalPages){

  Map<String, Object> data = new HashMap<>();
        data.put("total_pages", totalPages);
        data.put("read_pages", FieldValue.arrayUnion(currentPage));


        // Add read page to array (no duplicates)

        fireStoreDB.collection("user_" + user.getId).document("book_" + book.getId())
                .set(data, SetOptions.merge())
                .addOnSuccessListener(aVoid ->
                        Log.d("Activity", "FirestoreDB => updated read_pages " + currentPage))
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.d("Activity", "FirestoreDB => failed to update read_pages" + e);
                    }
                });


}

如何避免设置Firestore文档字段（如果已设置）

1 个答案: