是的，使用 DocumentSnapshot 可以在不存储的情况下获取 id.我将在这里尝试构建完整的示例.

Yes, it's possible to get id without storing it, using DocumentSnapshot. I will try to build complete examples here.

我创建了一个通用的 Model 类来保存 id:

I created a general Model class to hold the id:

@IgnoreExtraProperties
public class Model {
    @Exclude
    public String id;

    public <T extends Model> T withId(@NonNull final String id) {
        this.id = id;
        return (T) this;
    }
}

然后你可以用任何模型扩展它，不需要实现任何东西:

Then you extend it with any model, no need to implement anything:

public class Client extends Model

如果我在这里有客户列表，则尝试查询列表以仅获取 age == 20 的客户:

If I have list of clients here, trying to query the list to get only clients with age == 20:

clients.whereEqualTo("age", 20)
        .get()
        .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    for (DocumentSnapshot documentSnapshot : task.getResult().getDocuments()) {
                        // here you can get the id. 
                        Client client = document.toObject(client.class).withId(document.getId());
                       // you can apply your actions...
                    }
                } else {

                }
            }
        });

如果你使用EventListener，你也可以得到如下的id:

And if you are using EventListener, you can also get the id like the following:

clients.addSnapshotListener(new EventListener<QuerySnapshot>() {
    @Override
    public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
        for (DocumentChange change : documentSnapshots.getDocumentChanges()) {
            // here you can get the id. 
            QueryDocumentSnapshot document = change.getDocument();
            Client client = document.toObject(client.class).withId(document.getId());
                       // you can apply your actions...
        }
    }
});

documentSnapshot.getId()) 将获取集合中 Document 的 id，而无需将 id 保存到文档中.

documentSnapshot.getId()) will get you the id of the Document in the collection without saving the id into the document.

使用模型不会让您编辑任何模型，并且不要忘记使用 @IgnoreExtraProperties

Using Model will not let you edit any of your models, and don't forget using @IgnoreExtraProperties