Firestore 查询未获取最新文档

Question

I am currently building an Android application for a basic inventory management system for a haberdashery and the one feature/function I would like to implement is the ability to choose categories that when selected will filter the products. I am pretty much just playing around with the idea for now, but I currently have a CardView set up, where each Card contains a button that are labelled according to the category's name. I am currently using Google's Firestore to store all my information, which you can see below.

As you can see, there are 9 categories currently, each containg a different id value starting from 1 and ending on 9. I want to be able to add new categories within my application. So I figured that in order to add a new category, I first need to find the latest one that was added, obtain its id value, increment it by 1 and then write the new category with its new name(which is obtained through the application) and id to the database. This worked the first time, however if I start to consecutively add items the database it does not seem to find the latest document whenever I click the button to do so, for example, if the latest document is "ONAYBHFDTII6rcRbKxSf" with id value 9, then the first time will work whereby it will create a new document with id value 10, but when I try to add an 11th document, the query does not find the previously created document with id value 10, and instead uses document "ONAYBHFDTII6rcRbKxSf" again, giving me now two documents with id value 10, but with different category names.

I have pasted below the method I used to perform this action. This method is called in my button's onClickListener() . I first took in my new category name using an AlertDialog and then performed my read for the latest document by using an orderBy() and limit() method, to obtain the latest id, to which I then incremented and then wrote a new document back to the database.

I am still very new when it comes to Firestore/Firebase and I am trying to delve deeper into it, therefore my question is, am I doing something wrong? Is my logic out of place? If possible I would like to keep the structure of my database, but if it is absolutely necessary to change it in order for it to function properly then I won't mind.

private void showTextDialog(View view)
    {
        AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
        builder.setTitle("Enter Category");
        final EditText input = new EditText(getContext());
        input.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_DATETIME_VARIATION_NORMAL);
        builder.setView(input);

        builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                final String newCategory = input.getText().toString();
                db = FirebaseFirestore.getInstance();
                newCategories = new HashMap<>();
                db.collection("categories")
                        .orderBy("id", Query.Direction.DESCENDING)
                        .limit(1)
                        .get()
                        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                            @Override
                            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                                int latestID = 0;
                                for(QueryDocumentSnapshot document : task.getResult())
                                {
                                    latestID = Integer.parseInt(document.get("id").toString());
                                    Log.d("Latest Document", document.getId().toString());
                                }
                                latestID++;
                                newCategories.put("id", latestID);
                                newCategories.put("categoryName", newCategory);
                                db.collection("categories")
                                        .add(newCategories)
                                        .addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
                                            @Override
                                            public void onSuccess(DocumentReference documentReference) {
                                                Log.d("fragment", "Successfully added document");
                                                getCategories();
                                            }
                                        })
                                        .addOnFailureListener(new OnFailureListener() {
                                            @Override
                                            public void onFailure(@NonNull Exception e) {
                                                Log.d("fragment", "Failed to add document");
                                            }
                                        });
                            }
                        });


            }
        });
        builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });
        builder.show();
    }

Answer 1

I figured out the solution to my little problem stated above. Simply put, ensure that all the value in your database are exactly the same. In my case, some of the id values were strings and not number types