flutter - 从 firebase flutter 中的已知文档获取字段值

Question

我希望用户在我的应用程序中提供一个值并让其他用户看到它。但是我可以将数据上传到 firebase 但不能在另一端获取。我在 flutter 上启用了空安全。代码是:-

child: StreamBuilder(
stream:FirebaseFirestore.instance.collection('Collection name').doc('doc id').snapshots()
                  builder: (context, snapshot){
                    if(snapshot.hasData){
                      return Text(snapshot.data['Field name'].toString());  // here my editor shows error saying 'The method '[]' can't be unconditionally invoked because the receiver can be 'null'.' and asks for a null check and then shows error again
                    }
                    return Text('Nothing');
                  }
                ),

编辑:我只收到“type '_JsonDocumentSnapshot' is not a subtype of type 'Map ' in type cast”错误

如果我改变

if(snapshot.hasData){
                      return Text(snapshot.data['Field name'].toString()); 

到

if (snapshot.hasData) {
                        return Text(snapshot.data.toString());
                      }

我得到输出为“‘_JsonDocumentSnapshot’的实例”数据应该在哪里。我正在使用空检查飞镖

Answer 1

谢谢大家的支持，但是我无意中找到并回答了。我读到它的数据类型是 DocumentSnapshot，这对我有用

builder: (context, snapshot) {
                  if (snapshot.hasData) {
                    var numGuess = snapshot.data as DocumentSnapshot;
                    return Text(numGuess['Field name'].toString());
                  }
                  return Text('Nothing');
                }

This works for null safety.