您不需要自己存储时间戳.Firestore提供时间戳.请参见 https://pub.dev/documentation/cloud_firestore/latest/cloud_firestore/FieldValue/serverTimestamp.html

You don't need to store the timestamp by yourself. Firestore offers timestamp. See https://pub.dev/documentation/cloud_firestore/latest/cloud_firestore/FieldValue/serverTimestamp.html