我的钱包在更新 firebase 后拒绝显示余额

After updating this line in Future builder在 Future builder 中更新此行后

Container(
  child: FutureBuilder<DocumentSnapshot>(
    future: FirebaseFirestore.instance
        .collection("users")
        .doc(RitechApp.sharedPreferences
        .getString(RitechApp.userUID))
        .get(),
    builder: (c, snapshot) {
      if (!snapshot.hasData)
        return Center(
          child: CircularProgressIndicator(
            valueColor:
            new AlwaysStoppedAnimation<Color>(
                kPrimaryColor),
          ),
        );
      else {
        return Text(
          "KES" +
              snapshot..data.data["Wallet"]
                  .toString() ??
              0.toString(),
          style: TextStyle(
              fontSize: 25,
              fontFamily: "Muli",
              color: Colors.white),
        );
      }
    },
  ),
),

This following firebase database update and as well as observing null safety rules, I'm unable to retrieve wallet balance or update with each transaction.在 firebase 数据库更新以及遵守 null 安全规则之后，我无法检索钱包余额或更新每笔交易。 This is the code:这是代码：

Container(
  child: FutureBuilder<DocumentSnapshot>(
    future: FirebaseFirestore.instance
        .collection("users")
        .doc(RitechApp.sharedPreferences
            .getString(RitechApp.userUID))
        .get(),
    builder: (c, snapshot) {
      if (!snapshot.hasData)
        return Center(
          child: CircularProgressIndicator(
            valueColor:
                new AlwaysStoppedAnimation<Color>(kPrimaryColor),
          ),
        );
      else {
        return Text(
          "KES" + snapshot.data!["Wallet"].toString() ??
              0.toString(),
          style: TextStyle(
              fontSize: 25,
              fontFamily: "Muli",
              color: Colors.white),
        );
      }
    },
  ),
),

I'm unable to retrieve wallet balance or update with each transaction.我无法检索钱包余额或更新每笔交易。 This is the code.这是代码。

Create a state variable for future like为未来创建一个 state 变量

  late final myFuture = FirebaseFirestore.instance
      .collection("users")
      .doc(RitechApp.sharedPreferences.getString(RitechApp.userUID))
      .get();

and use FutureBuiler like this, you will get error message if something fails并像这样使用 FutureBuiler，如果出现故障，您将收到错误消息

child: FutureBuilder<DocumentSnapshot?>(
  future: myFuture,
  builder: (c, snapshot) {
    if (snapshot.hasData) {
     // 
      return Text(
        // "KES ${snapshot.data?["Wallet"] ?? 0} ",
         "KES ${snapshot.data?.get("Wallet") ?? 0}",
        style: TextStyle(
            fontSize: 25, fontFamily: "Muli", color: Colors.white),
      );
    } else if (snapshot.hasError) {
      return Text(" ${snapshot.error}");
    } else {
      return Center(
        child: CircularProgressIndicator(
          valueColor: new AlwaysStoppedAnimation<Color>(Colors.red),
        ),
      );
    }
  },
),