解决Firebase数据类型转换错误：String到Int的映射问题与实践

com.google.firebase.database.DatabaseException: Failed to convert a value of type java.lang.String to int
    at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertInteger(CustomClassMapper.java:364)
    at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToPrimitive(CustomClassMapper.java:290)
    // ... (更多堆栈信息，指向DataSnapshot.getValue调用处)
    at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
    at com.example.guided_app.fragment.exploreFragment$1.onDataChange(exploreFragment.java:60)

public class User {
    // ... 其他字段
    private int guidedCount; // 在Java模型中定义为int类型
    // ... 构造函数、其他getter和setter

    public int getGuidedCount() {
        return guidedCount;
    }
    public void setGuidedCount(int guidedCount) {
        this.guidedCount = guidedCount;
    }
    // ...
}

"Users": {
    "gAzcrP1IYmQI0ht4qfH9WGt9U7F2": {
      "cname": "MIT",
      "email": "...",
      "guided": { ... },
      "guidedCount": "gAzcrP1IYmQI0ht4qfH9WGt9U7F2", // 错误：这里是一个String，而非int
      "name": "John Adams",
      "password": "123456",
      "profession": "Developer @ Apple"
    },
    "y3pV1GhdLqOnteMO64U2F4o8mMu2": {
      "cname": "BIT",
      "email": "...",
      "guided": { ... },
      "guidedCount": 1, // 正确：int类型
      "name": "Kumar Mishra",
      "password": "123456",
      "profession": "SDE @ Microsoft"
    }
    // ... 其他用户
}

// 示例：在写入数据前进行验证
public void updateUserGuidedCount(String userId, int count) {
    if (count < 0) {
        // 可以选择抛出异常、记录错误日志或设置默认值，防止写入无效数据
        Log.w("FirebaseWrite", "Attempted to set negative guidedCount for user: " + userId);
        count = 0; // 设置默认值
    }
    database.getReference().child("Users").child(userId).child("guidedCount").setValue(count)
            .addOnSuccessListener(aVoid -> Log.d("FirebaseWrite", "guidedCount updated successfully for " + userId))
            .addOnFailureListener(e -> Log.e("FirebaseWrite", "Failed to update guidedCount for " + userId, e));
}

{
  "rules": {
    "Users": {
      "$uid": { // $uid 代表每个用户ID
        "guidedCount": {
          ".validate": "newData.isNumber() && newData.val() >= 0" // 强制guidedCount必须是数字且非负
        },
        // ... 其他字段的规则
        ".read": "auth != null", // 示例：只有认证用户才能读取
        ".write": "auth != null && auth.uid == $uid" // 示例：用户只能写入自己的数据
      }
    }
  }
}

// 在exploreFragment的onDataChange方法中
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
    list.clear();
    for(DataSnapshot dataSnapshot : snapshot.getChildren()){
        // 打印原始数据，有助于调试，查看其结构和类型
        Log.d("FirebaseData", "Processing user key: " + dataSnapshot.getKey() + ", Raw data: " + dataSnapshot.getValue());

        try {
            User user = dataSnapshot.getValue(User.class);
            if (user != null) {
                user.setUserID(dataSnapshot.getKey()); // 设置用户ID
                if(!dataSnapshot.getKey().equals(FirebaseAuth.getInstance().getUid())){
                    list.add(user);
                }
            }
        } catch (DatabaseException e) {
            // 捕获并记录类型转换异常，指明哪个key的数据有问题
            Log.e("FirebaseError", "Failed to convert user data for key: " + dataSnapshot.getKey() + ". Error: " + e.getMessage(), e);
            // 可以选择跳过此条错误数据，或为该用户创建一个默认User对象，以防止应用崩溃
        }
    }
    adapter.notifyDataSetChanged();
}