关于 Flutter State 和从 State 与 StatefulWidget 检索变量的问题

Question

Here's the context :

In my app, users can create a question, and all questions will be displayed on a certain page. This is done with a ListView.builder whose itemBuilder property returns a QuestionTile.

The problem :

If I create a new question, the text of the new question is (usually) displayed as the text of the previous question.

Here's a picture of me adding three questions in order, "testqn123", "testqn456", "testqn789" , but all are displayed as "testqn123" .

Hot restarting the app will display the correct texts for each question, but hot reloading wont work.

In my _QuestionTileState class, if I change the line responsible for displaying the text of the question on the page, from

child: Text(text)

to

child: Text(widget.text)

the issue will be resolved for good. I'm not super familiar with how hot restart/reload and state works in flutter, but can someone explain all of this?

Here is the code for QuestionTile and its corresponding State class, and the line changed is the very last line with words in it :

class QuestionTile extends StatefulWidget {
  final String text;
  final String roomName; 
  final String roomID; 
  final String questionID; //

  QuestionTile({this.questionID, this.text, this.roomName, this.roomID});

  @override
  _QuestionTileState createState() => _QuestionTileState(text);
}

class _QuestionTileState extends State<QuestionTile> {
  final String text;
  int netVotes = 0;
  bool expand = false;
  bool alreadyUpvoted = false;
  bool alreadyDownvoted = false;

  _QuestionTileState(this.text);

  void toggleExpansion() {
    setState(() => expand = !expand);
  }

  @override
  Widget build(BuildContext context) {
    RoomDbService dbService = RoomDbService(widget.roomName, widget.roomID);
    final user = Provider.of<User>(context);

    print(widget.text + " with questionID of " + widget.questionID);

    return expand
        ? ExpandedQuestionTile(text, netVotes, toggleExpansion)
        : Card(
            elevation: 10,
            child: Padding(
              padding: const EdgeInsets.fromLTRB(10, 7, 15, 7),
              child: GestureDetector(
                onTap: () => {
                  Navigator.pushNamed(context, "/ChatRoomPage", arguments: {
                    "question": widget.text,
                    "questionID": widget.questionID,
                    "roomName": widget.roomName,
                    "roomID": widget.roomID,
                  })
                },
                child: new Row(
                  // crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: <Widget>[
                    Column(
                      // the stack overflow functionality
                      children: <Widget>[
                        InkWell(
                          child: alreadyUpvoted
                              ? Icon(Icons.arrow_drop_up,
                                  color: Colors.blue[500])
                              : Icon(Icons.arrow_drop_up),
                          onTap: () {
                            dynamic result = dbService.upvoteQuestion(
                                user.uid, widget.questionID);
                            setState(() {
                              alreadyUpvoted = !alreadyUpvoted;
                              if (alreadyDownvoted) {
                                alreadyDownvoted = false;
                              }
                            });
                          },
                        ),
                        StreamBuilder<DocumentSnapshot>(
                          stream: dbService.getQuestionVotes(widget.questionID),
                          builder: (context, snapshot) {
                            if (!snapshot.hasData) {
                              return Center(child: CircularProgressIndicator());
                            } else {
                              // print("Current Votes: " + "${snapshot.data.data["votes"]}");
                              // print("questionID: " + widget.questionID);
                              return Text("${snapshot.data.data["votes"]}");
                            }
                          },
                        ),
                        InkWell(
                          child: alreadyDownvoted
                              ? Icon(Icons.arrow_drop_down,
                                  color: Colors.red[500])
                              : Icon(Icons.arrow_drop_down),
                          onTap: () {
                            dbService.downvoteQuestion(
                                user.uid, widget.questionID);
                            setState(() {
                              alreadyDownvoted = !alreadyDownvoted;
                              if (alreadyUpvoted) {
                                alreadyUpvoted = false;
                              }
                            });
                          },
                        ),
                      ],
                    ),

                    Container(
                      //color: Colors.red[100],
                      width: 290,
                      child: Align(
                          alignment: Alignment.centerLeft,
                          child: Text(text)), // problem solved if changed to Text(widget.text)
                    ),

                   

                    

  }
}

Answer 1

You can wrap your UI with a Stream Builder, this will allow the UI to update every time any value changes from Firestore.

Since you are using an item builder you can wrap the widget that is placed with the item builder.

That Should update the UI