带子句WhereEqualTo的Firestore查询始终返回空结果

Question

我正在尝试在一个字段上使用子句WhereEqualTo在Android Firebase Cloud Firestore中获取集合中的一个文档，但是我不知道为什么有时候在数据库中有相同数据时会得到空结果。

有时结果为空。当我删除whereEqualTo子句时，我得到了所有集合。

这是我的要求

public static Task<QuerySnapshot> getUserByEmail() {
        String email = "mireille@sombux.com";
        return UserHelper.getUsersCollection()
                .whereEqualTo("email", email)
                .get();
    }

这是我的用户类

public abstract class User {
    private long id;
    private String email;
    private Date lastLogin;
    private Date birthday;
    private String country;
    private String codcountry;
    private String formation;
    private String drink;
    private String about;

    public User() {}

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Date getLastLogin() {
        return lastLogin;
    }

    public void setLastLogin(Date lastLogin) {
        this.lastLogin = lastLogin;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }

    public String getCodcountry() {
        return codcountry;
    }

    public void setCodcountry(String codcountry) {
        this.codcountry = codcountry;
    }

    public String getFormation() {
        return formation;
    }

    public void setFormation(String formation) {
        this.formation = formation;
    }

    public String getDrink() {
        return drink;
    }

    public void setDrink(String drink) {
        this.drink = drink;
    }

    public String getAbout() {
        return about;
    }

    public void setAbout(String about) {
        this.about = about;
    }

这是我的数据

我这样使用它

UserHelper.getUserByEmail().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    for (DocumentSnapshot document : task.getResult()) {
                        final User remoteUser = document.toObject(User.class);
                        if (remoteUser != null) {
                            Toast.makeText(context, "Find", Toast.LENGTH_SHORT).show();
                            // do something
                        }
                        return;
                    }
                    Toast.makeText(context, "Not find", Toast.LENGTH_SHORT).show();
                }
            }
        });