Flutter firestore -检查文档ID是否已存在

import 'package:cloud_firestore/cloud_firestore.dart';

final FirebaseFirestore firestore = FirebaseFirestore.instance;

final CollectionReference collection = firestore.collection('your_collection');
final DocumentReference document = collection.doc('your_document_id');

document.get().then((DocumentSnapshot snapshot) {
  if (snapshot.exists) {
    // 文档已存在
    print('Document exists.');
  } else {
    // 文档不存在
    print('Document does not exist.');
  }
}).catchError((error) {
  // 处理错误
  print('Error: $error');
});