How to make a sparkline stateful widget to add new points along the time in flutter?

Question

I have a stateful widget that draws a one from a list of points stored locally:

class Sparkline extends StatefulWidget {

    @override
    _Sparkline create() => _Sparkline;
}

class _Sparkline extends State<Sparkline> {
    List<Offset> _points = [];

    /// Add a new value and redraw
    void add(double value) { 
        SetState(() {
             points.add(value);
        });
    }

    @override
    void build(BuildState context) {
        /// My sparkling custom painter that draw all points
        return CustomPainter(...);
    }
}

My idea would be to invoke the _Sparkline add() function anytime I've got a new value so that the sparkline redraws.

What's the best way to do that?

Answer 1

Finally, I updated my code to take advantage of a Stream as follows (The stream itself was created elsewhere and is to be passed to the Sparkline widget):

class Sparkline extends StatefulWidget {
    late final StreamController<double> streamController;

    Sparkline({required this.streamController});

    @override
    _Sparkline create() => _Sparkline;
}

class _Sparkline extends State<Sparkline> {

    /// List of points to be drawn
    List<Offset> _points = [];

    /// Subscription to the value stream
    late StreamSubscription<double> _subscription;

    @override
    void initState() {
        super.initState();
    
        // Subscribe to the stream of points
        _subscription = widget.streamController.stream.listen((value) {
            setState(() {
                points.add(point);
            });
        });
    }

    @override
    void dispose() {
        _subscription.cancel();
        super.dispose();
     }


    @override
    void build(BuildState context) {
        /// My sparkling custom painter that draw all points
        return CustomPainter(...);
    }
}
``