Kotlin 如何从 Firestore 查询中排除元素

After days and days of struggling with this issue, I finally found the answer. I could not solve this without the help of @Raj. Thank you so much @Raj for the patience and guidance.

First off all, according to the answer provided by @Frank van Puffelen in his answer from this post, I stopped searching for a solution that can help me pass two queries to a single adapter.

在这个问题中，我想要实现的就是查询数据库以获得除我之外的所有用户.因此，因为我们不能将两个查询组合成一个实例，所以我发现我们可以将两个查询的结果组合在一起.因此，我创建了两个查询:

FirebaseFirestore db = FirebaseFirestore.getInstance();
Query firstQuery = db.collection("users").whereLessThan("uid", uid);
Query secondQuery = db.collection("users").whereGreaterThan("uid", uid);

I'm having a UserModel (POJO) class for my user object. I found not one, but two ways to solve the problem. The first one would be to query the database to get all user objects that correspond to the first criteria and add them to a list. After that, query the database again and get the other user objects that correspond to the second criteria and add them to the same list. Now I have a list that contains all the users that I need but one, the one with that particular id from the queries. This is the code for future visitors:

firstQuery.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
    @Override
    public void onComplete(@NonNull Task<QuerySnapshot> task) {
        List<UserModel> list = new ArrayList<>();
        if (task.isSuccessful()) {
            for (DocumentSnapshot document : task.getResult()) {
                UserModel userModel = document.toObject(UserModel.class);
                list.add(userModel);
            }

            secondQuery.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                @Override
                public void onComplete(@NonNull Task<QuerySnapshot> task) {
                    if (task.isSuccessful()) {
                        for (DocumentSnapshot document : task.getResult()) {
                            UserModel userModel = document.toObject(UserModel.class);
                            list.add(userModel);
                        }

                        //Use the list of users
                    }
                }
            });
        }
    }
});

The second approach would be much shorter because I use Tasks.whenAllSuccess() like this:

Task firstTask = firstQuery.get();
Task secondTask = secondQuery.get();

Task combinedTask = Tasks.whenAllSuccess(firstTask, secondTask).addOnSuccessListener(new OnSuccessListener<List<Object>>() {
        @Override
        public void onSuccess(List<Object> list) {
            //This is the list that I wanted
        }
});