How to properly feed data to StreamBuilder initialData parameter?

Question

I am using a StreamBuilder widget to display some data. When the app is recently opened, I wanted to display some initial data from my json file and feed it into the initialData optional keyword parameter of StreamBuilder.

Here is how I feed it:

MyStorage m = new MyStorage(); // Using path_provider, I accessed the json file inside this class
int x;

@override
void initState(){
    super.initState();
    getData();
}

getData() async{
    Map<String, dynamic> myMap = await m._getMap;
    x = int.parse(myMap["total"]);
}

...

@override
Widget build(BuildContext context){
    ...

    child: StreamBuilder(
        stream: mystream, // coming from my BLoC class
        initialData: x,
        builder: (context, snapshot){
            return new Text("${snapshot.data}");
        }
...

The problem is it that the Text widget inside my StreamBuilder is displaying "null".

I tried to rewrite my code to this:

MyStorage m = new MyStorage();

Future<int> getData() async{
    Map<String, dynamic> myMap = await m._getMap;
    return int.parse(myMap["total"]);
}

...

@override
Widget build(BuildContext context){
    ...

    child: StreamBuilder(
        stream: mystream, // coming from my BLoC class
        initialData: getData(),
        builder: (context, snapshot){
            return new Text("${snapshot.data}");
        }

...

but it displayed on my Text widget as "Instance of Future:int"

I have no problem with my stream parameter in the StreamBuilder. It displays the correct value that I'm expecting from the BLoC class.

The only problem I had is the feeding of initialData from my json file.

What am I doing wrong? I would appreciate any kind of help. Thanks

[UPDATE]

After a long hours of thinking a solution, I gave up using initialData parameter since after I added int to StreamBuilder like this StreamBuilder<int>() it prompted me that it will only take a value of integer. I couldn't fed it with a type of Future or Stream so I decided not to use it. What I did was I nested a FutureBuilder inside the StreamBuilder through ConnectionState.

Here is what my code now:

MyStorage m = new MyStorage();

Future<int> getData() async{
    Map<String, dynamic> myMap = await m._getMap;
    return int.parse(myMap["total"]);
}

...

@override
Widget build(BuildContext context){
    ...

    child: StreamBuilder<int>(
        stream: mystream, // coming from my BLoC class
        //initialData: getData(),
        builder: (context, snapshot){
            swith(snapshot.connectionState){
                case ConnectionState.none:
                    return new FutureBuilder(
                        future: getData(),
                        builder: (context, snapshot){
                            return new Text('${snapshot.data}');
                        }
                    );
                case ConnectionState.active:
                case ConnectionState.waiting:
                    return new FutureBuilder(
                        future: getData(),
                        builder: (context, snapshot){
                            return new Text('${snapshot.data}');
                        }
                    );
                case ConnectionState.done:
                    if (snapshot.hasData){
                        return new Text('${snapshot.data}');
                    }
                    return new FutureBuilder(
                        future: getData(),
                        builder: (context, snapshot){
                            return new Text('${snapshot.data}');
                        }
                    );
            }
        }

...

I know that this solution is very inefficient but I couldn't think of a better solution as of now.

Answer 1

initialData is supposed to be the data to show before your actual data is available.

place 0 as initialData.

StreamBuilder has an additional parameter stream which is responsible for fetching your stream data. here you can do stream: getData().asStream,

edit:

Also make sure to specify the type of data you are expecting in your StreamBuilder. StreamBuilder<int>()