如何使用firestore在android studio中检索特定用户的数据

implementation 'com.google.firebase:firebase-firestore:23.0.0'

classpath 'com.google.gms:google-services:4.3.10'

apply plugin: 'com.google.gms.google-services'

FirebaseFirestore db = FirebaseFirestore.getInstance();

String userId = "特定用户的ID";
DocumentReference docRef = db.collection("users").document(userId);

docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            DocumentSnapshot document = task.getResult();
            if (document.exists()) {
                // 用户数据存在
                // 可以通过document对象获取数据
                String username = document.getString("username");
                int age = document.getLong("age").intValue();
                // ...
            } else {
                // 用户数据不存在
            }
        } else {
            // 获取数据失败
        }
    }
});