Flutter新手求助：如何基于Firebase Authentication用户ID存储财务追踪应用交易数据至Firebase Database

Hey there! Let's get your transaction data tied to each user's ID—this is a common pattern with Firebase, and it's totally manageable even as a Flutter beginner. Here's how to adjust your code and structure things properly:

Step 1: Restructure Your Firebase Database #

Right now, you're storing all transactions directly under a Transaction node. Instead, we'll create a user-specific structure:
Transactions -> [USER_UID] -> [TRANSACTION_PUSH_ID]
This keeps each user's data isolated and makes it easy to fetch only their transactions later.

Step 2: Update the saveRecord Method #

You already have code to get the current user—we just need to use that uid to target the right database node. Here's the revised method with explanations:

void saveRecord() async {
  // Get the currently logged-in user
  User? user = await auth.currentUser;
  
  // Make sure the user is actually logged in before saving
  if (user == null) {
    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('Please log in first to save transactions!')),
    );
    return;
  }

  String dates = date.text;
  String values = amount.text;
  String descriptions = description.text;

  Map<String, String> transaction = {
    'dates': dates,
    'amount': 'RM' + values,
    'category': selectExpense,
    'descriptions': descriptions,
    // Optional: Store the user ID in the transaction itself for extra clarity
    'userId': user.uid,
  };

  // Create a reference to the current user's transaction node
  DatabaseReference userTransactionsRef = FirebaseDatabase.instance
      .reference()
      .child('Transactions')
      .child(user.uid);
  
  // Push the transaction to their personal node
  userTransactionsRef.push().set(transaction).then((value) {
    Navigator.pop(context, TransactionDaily());
    ScaffoldMessenger.of(context).showSnackBar(
      const SnackBar(content: Text('Transaction saved successfully!')),
    );
  }).catchError((error) {
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Failed to save: ${error.toString()}')),
    );
  });
}

Step 3: (Critical) Set Up Firebase Security Rules #

To make sure users can only access their own data, update your Firebase Realtime Database rules to this:

{
  "rules": {
    "Transactions": {
      "$uid": {
        ".read": "auth != null && auth.uid == $uid",
        ".write": "auth != null && auth.uid == $uid"
      }
    }
  }
}

This blocks any unauthorized access to other users' transactions.

Step 4: Fetching User Transactions (Bonus!) #

When you want to display the user's transactions later, you'll fetch from their specific node like this:

void loadUserTransactions() async {
  User? user = await auth.currentUser;
  if (user == null) return;

  DatabaseReference userTransactionsRef = FirebaseDatabase.instance
      .reference()
      .child('Transactions')
      .child(user.uid);

  // Listen for real-time updates to the user's transactions
  userTransactionsRef.onValue.listen((event) {
    DataSnapshot snapshot = event.snapshot;
    if (snapshot.value != null) {
      Map<dynamic, dynamic> transactionMap = snapshot.value as Map;
      // Convert the map to a list of transaction objects for your UI
      List<dynamic> userTransactions = transactionMap.values.toList();
      // Update your state with the transactions here
    }
  });
}

This setup ensures every transaction is linked to the user who created it, keeps data secure, and makes it easy to manage per-user records.

内容的提问来源于stack exchange，提问作者New user