优化FirestoreRecyclerAdapter的数据过滤与计数刷新

myStudentAdapter = new MyStudentAdapter(options) {
    @Override
    public void onDataChanged() {
        super.onDataChanged();
        // 当适配器数据发生变化时，更新总数显示
        tv_total.setText(String.valueOf(getItemCount()));
    }
};

// 假设这是您根据筛选条件构建的查询
Query filteredQuery = db.collection("Student")
        .whereEqualTo("course", "Computer Science")
        .whereEqualTo("year", "2023");

filteredQuery.count().get().addOnSuccessListener(snapshot -> {
    long count = snapshot.getCount(); // 获取匹配文档的总数
    tv_total.setText(String.valueOf(count));
}).addOnFailureListener(e -> {
    // 处理错误
    Log.e("FirestoreCount", "Error getting count: " + e.getMessage());
});

public class MyStudentActivity extends AppCompatActivity {

    private FirebaseFirestore db;
    private RecyclerView rv;
    private MyStudentAdapter myStudentAdapter;
    private TextView tv_total;

    // 假设这些是用户输入的筛选条件
    private String currentSearch = "";
    private String currentCourse = "";
    private String currentYear = "";
    private String currentBlock = "";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        db = FirebaseFirestore.getInstance();
        rv = findViewById(R.id.rv);
        tv_total = findViewById(R.id.tv_total);

        rv.setLayoutManager(new LinearLayoutManager(this));

        // 首次加载数据
        applyFilterAndRefreshData(currentSearch, currentCourse, currentYear, currentBlock);

        // 假设有按钮或输入框来改变筛选条件
        findViewById(R.id.btn_apply_filter).setOnClickListener(v -> {
            // 获取用户新的筛选条件
            currentSearch = "new_search_term"; // 示例
            currentCourse = "new_course";     // 示例
            // ... 更新其他条件 ...

            applyFilterAndRefreshData(currentSearch, currentCourse, currentYear, currentBlock);
        });
    }

    private Query createFilteredQuery(String search, String course, String year, String block) {
        CollectionReference studentsRef = db.collection("Student");
        Query query = studentsRef.orderBy("fullName");

        if (!course.isEmpty()) {
            query = query.whereEqualTo("course", course);
        }
        if (!year.isEmpty()) {
            query = query.whereEqualTo("year", year);
        }
        if (!block.isEmpty()) {
            query = query.whereEqualTo("block", block);
        }

        if (!search.isEmpty()) {
            query = query.startAt(search).endAt(search + '\uf8ff');
        }
        return query;
    }

    private void applyFilterAndRefreshData(String search, String course, String year, String block) {
        Query newQuery = createFilteredQuery(search, course, year, block);

        FirestoreRecyclerOptions<Student> newOptions = new FirestoreRecyclerOptions.Builder<Student>()
                .setQuery(newQuery, Student.class)
                .build();

        if (myStudentAdapter != null) {
            myStudentAdapter.updateOptions(newOptions);
        } else {
            myStudentAdapter = new MyStudentAdapter(newOptions) {
                @Override
                public void onDataChanged() {
                    super.onDataChanged();
                    tv_total.setText(String.valueOf(getItemCount()));
                }
            };
            rv.setAdapter(myStudentAdapter);
            myStudentAdapter.startListening();
        }

        // 也可以同时获取独立计数
        newQuery.count().get().addOnSuccessListener(snapshot -> {
            long count = snapshot.getCount();
            Log.d("FirestoreCount", "Filtered count via Query.count(): " + count);
        }).addOnFailureListener(e -> {
            Log.e("FirestoreCount", "Error getting count for new query: " + e.getMessage());
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        if (myStudentAdapter != null) {
            myStudentAdapter.startListening();
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (myStudentAdapter != null) {
            myStudentAdapter.stopListening();
        }
    }
}