getUsername和电话返回空数据快照

Question

我曾尝试建立实时租车服务，但我得到此错误，返回null的datasnapshot，并尝试了所有修复问题，但没有成功 我不知道问题出在哪里，为什么我的数据库不响应请求

 DatabaseReference driverLocation = FirebaseDatabase.getInstance().getReference(Common.driver_location_tbl);
    GeoFire gf = new GeoFire(driverLocation);

    GeoQuery geoQuery = gf.queryAtLocation(new GeoLocation(mLastLocation.getLatitude(),mLastLocation.getLongitude()),distance);
    geoQuery.removeAllListeners();

    geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
        @Override
        public void onKeyEntered(final String key, final GeoLocation location) {
            FirebaseDatabase.getInstance().getReference(Common.driver_tbl)
                    .child(key)
                    .addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            Rider rider = dataSnapshot.getValue(Rider.class);





                            mMap.addMarker(new MarkerOptions()
                                    .position(new LatLng(location.latitude,location.longitude))
                                    .flat(true)
                                    .title("Driver Name :"+rider.getUsername())
                                    .snippet("Phone : "+rider.getPhone())
                                    .icon(BitmapDescriptorFactory.fromResource(R.drawable.cars)));
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {

                        }
                    });
        }

和我的Rider班

public class Rider {
private String email,password,phone,username;

public Rider() {
}

public Rider(String email, String password, String phone, String username) {
    this.email = email;
    this.password = password;
    this.phone = phone;
    this.username = username;
}

public String getEmail() {
    return email;
}

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

public String getPassword() {
    return password;
}

public void setPassword(String password) {
    this.password = password;
}

public String getPhone() {
    return phone;
}

public void setPhone(String phone) {
    this.phone = phone;
}

public String getUsername() {
    return username;
}

public void setUsername(String username) {
    this.username = username;
}

如何修复应用程序漏洞并返回null的数据快照？ 我正在研究修复方法，但没有发现任何东西。

Answer 1

好，我修复了它 问题是我用不Uid的名称注册用户，所以当我请求名称和电话得到n

时