Firestore新增数据时RecyclerView自动刷新的原因与阻止方案

向Firestore数据库添加新Student数据时，RecyclerView现有条目会被全部刷新。每次新增学生数据，Firestore都会返回Student集合的所有文档，如何避免这种情况？

现有代码 #

private void load() {
    Query query = createQuery();
    FirestoreRecyclerOptions<Student> options = new FirestoreRecyclerOptions.Builder<Student>()
            .setQuery(query, Student.class)
            .build();

    myStudentAdapter = new MyStudentAdapter(options);
    rv.setAdapter(myStudentAdapter);
    myStudentAdapter.startListening();
}

private Query createQuery() {
    if (!search.isEmpty()) {
        if (!course.isEmpty() && !year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("year", year)
                    .whereEqualTo("block", block)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (!course.isEmpty() && !year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("year", year)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (!course.isEmpty() && year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("block", block)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (course.isEmpty() && !year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("year", year)
                    .whereEqualTo("block", block)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (!course.isEmpty() && year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (course.isEmpty() && !year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("year", year)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else if (course.isEmpty() && year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("block", block)
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        } else {
            return db.collection("Student")
                    .orderBy("fullName")
                    .startAt(search)
                    .endAt(search + '\uf8ff');
        }
    } else {
        if (!course.isEmpty() && !year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("year", year)
                    .whereEqualTo("block", block);
        } else if (!course.isEmpty() && !year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("year", year);
        } else if (!course.isEmpty() && year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course)
                    .whereEqualTo("block", block);
        } else if (course.isEmpty() && !year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("year", year)
                    .whereEqualTo("block", block);
        } else if (!course.isEmpty() && year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("course", course);
        } else if (course.isEmpty() && !year.isEmpty() && block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("year", year);
        } else if (course.isEmpty() && year.isEmpty() && !block.isEmpty()) {
            return db.collection("Student")
                    .orderBy("fullName")
                    .whereEqualTo("block", block);
        } else {
            return db.collection("Student")
                    .orderBy("fullName");
        }
    }
}

@Override
public void onStart() {
    super.onStart();
    myStudentAdapter.startListening();
}

@Override
public void onStop() {
    super.onStop();
    myStudentAdapter.stopListening();
}

1. 避免重复创建Adapter实例 #

当前load()方法每次都会新建FirestoreRecyclerOptions和MyStudentAdapter，还会调用rv.setAdapter()，这会强制RecyclerView完全刷新。改成只初始化一次Adapter，后续仅更新查询条件：

// 全局变量保存Adapter和Options
private FirestoreRecyclerOptions<Student> options;
private MyStudentAdapter myStudentAdapter;

// 在onCreate等初始化方法中创建Adapter
private void initRecyclerView() {
    Query initialQuery = createQuery();
    options = new FirestoreRecyclerOptions.Builder<Student>()
            .setQuery(initialQuery, Student.class)
            .build();

    myStudentAdapter = new MyStudentAdapter(options);
    rv.setAdapter(myStudentAdapter);
    myStudentAdapter.startListening();
}

// 需要更新查询时，仅修改Options并通知Adapter
private void refreshQuery() {
    Query newQuery = createQuery();
    options = options.toBuilder().setQuery(newQuery).build();
    myStudentAdapter.updateOptions(options);
}

2. 依赖Firestore实时监听的增量更新 #

Firestore实时监听默认只会返回发生变化的文档（新增/修改/删除），但如果每次都重建Adapter，就会触发全量加载。保持Adapter实例不变，Firestore会自动处理增量数据，RecyclerView也只会刷新对应条目。

3. 检查Adapter实现 #

确保MyStudentAdapter正确继承FirestoreRecyclerAdapter，且onBindViewHolder仅做必要的UI绑定操作，不要手动调用notifyDataSetChanged()，让Firestore的Adapter自动管理更新逻辑。

内容的提问来源于stack exchange，提问作者Vince Ybañez