How Do I Use RefreshIndicator with a FutureBuilder in Flutter?

Question

I'm trying to figure out a way to indicate to a surrounding class when the FutureBuilder is done loading. RefreshIndicator takes a Future as a parameter and stops showing the refresh indicator when the Future completes. I don't have access to the exact same Future variable that's being passed to the FutureBuilder, especially when these are in two separate classes, unless I can pass a reference to one and when it completes in the other class, I'll know...

Answer 1

I'm searching for this answer too. Finally i figured it out...

Here is how i done

FutureBuilder<String>(
        future: _calculation,
        // a previously-obtained Future<String> or null
        builder: (BuildContext context,
            AsyncSnapshot<String> snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.none:
              return Text('Press button to start.');
            case ConnectionState.active:
            case ConnectionState.waiting:
              return Text('Awaiting result...');
            case ConnectionState.done:
              if (snapshot.hasError)
                return Text('Error: ${snapshot.error}');
              return new RefreshIndicator(
                  key: _refreshIndicatorKey,
                  color: Colors.blue,
                  onRefresh: () {
                    return _calculation = getCalculation(); // EDITED
                  },
                  child: SingleChildScrollView(
                      physics: AlwaysScrollableScrollPhysics(),
                      child: Text('Result: ${snapshot.data}')
                  )


              );
              break;
            default:
              return null;
          }
        },
      )
 

Future<String> getCalculation() async {
    try {
      /*Write your API here or what ever u want to get when pull to refresh*/
      return ""/*the value of api*/; //EDITED

    } catch (e) {
      ///Handle Exception here. So in FutureBuilder we can capture it in snapshot.hasError
      return Future.error(e.toString());
    }
  }




      

Answer 2

You have to access the snapshot, provided builder parm:

So, snapshot.data gives you the Future.

new FutureBuilder<String>(
  future: _calculation, // a Future<String> or null
  builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
    switch (snapshot.connectionState) {
      case ConnectionState.none: return new Text('Press button to start');
      case ConnectionState.waiting: return new Text('Awaiting result...');
      default:
        if (snapshot.hasError)
          return new Text('Error: ${snapshot.error}');
        else
          return new Text('Result: ${snapshot.data}');
    }
  },
)

Example: https://flutter.io/cookbook/networking/background-parsing/

Doc: https://docs.flutter.io/flutter/widgets/FutureBuilder-class.html