Streambuilder - flutter 迁移后出错 - 快照语法

Question

我在迁移之前使用了这段代码

StreamBuilder(
          stream: FirebaseDatabase.instance
              .ref()
              .child('user')
              .child(_userID)
              .onValue,
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              _networkImageUrl = snapshot.data.snapshot.value["img"];
              return Text(_networkImageUrl.toString());
             } else {
               return Container();
            }
          }),

在“dart pub upgrade --null-safety”之后出现错误：

The property 'snapshot' can't be unconditionally accessed because the receiver can be 'null'.

我试着用“！”修复它但它不起作用，它保持相同的错误

Answer 1

这是代码的工作原理：

StreamBuilder<DatabaseEvent>(
          stream: FirebaseDatabase.instance
              .ref()
              .child('user')
              .child(_userID)
              .onValue,
          builder: (BuildContext context,AsyncSnapshot snapshot) {
            if (snapshot.hasData) {
              Map<dynamic, dynamic> userDocument = snapshot.data.snapshot.value;
              _networkImageUrl = userDocument["img"]
              return Text(_networkImageUrl.toString());
             } else {
               return Container();
            }
          }),

thx 2 h8moss

Streambuilder - flutter 迁移后出错 - 快照语法

Streambuilder - error after flutter migration - snapshot syntax

flutter

dart

dart-null-safety