Swap a Flare image at runtime.

dynamic_image_swapping.dart

import 'dart:async';
import 'dart:typed_data';

import 'package:flare_dart/math/mat2d.dart';
import 'package:flare_flutter/flare.dart';
import "package:flare_flutter/flare_actor.dart";
import 'package:flare_flutter/flare_controller.dart';
import "package:flutter/material.dart";
import 'package:flutter/services.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flare Demo',
      theme: ThemeData(primarySwatch: Colors.blue),
      home: MyHomePage(title: 'Flare-Flutter'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String _animationName = "idle";
  ImageSwapController _imageSwapper = ImageSwapController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.grey,
      appBar: AppBar(title: Text(widget.title)),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          mainAxisSize: MainAxisSize.min,
          children: [
            Expanded(
              child: FlareActor(
                "assets/ImageSwap.flr",
                controller: _imageSwapper,
                alignment: Alignment.center,
                fit: BoxFit.contain,
                animation: _animationName,
              ),
            )
          ],
        ),
      ),
    );
  }
}

class ImageSwapController extends FlareController {
  @override
  bool advance(FlutterActorArtboard artboard, double elapsed) {
    return false;
  }

  @override
  void initialize(FlutterActorArtboard artboard) {
    var node = artboard.getNode("avatar2");
    if (node is FlutterActorImage) {
      // Change it with a bundled image.
      node.changeImageFromBundle(rootBundle, "assets/c.png").then((bool ok) {
        // Because changeImageFromBundle is async, the FlareActor will have
        // already drawn with the existing image. Since this example has no
        // animation, it will have stopped re-drawing. So we need to let
        // the FlareActor know that we want to re-draw with the new image.
        isActive.value = true;
      });

      // ...or change it with a network image
      node
          .changeImageFromNetwork("https://picsum.photos/250?image=9")
          .then((bool ok) {
        isActive.value = true;
      });
    }
  }

  @override
  void setViewTransform(Mat2D viewTransform) {}
}

/// Add an extension method to FlutterActorImage to change the image 
/// with one downloaded from the network.
/// This is implemented as an extension method as the dev/master
/// signature for PaintingBinding.instance.instantiateImageCodec is 
/// different from the one in stable.
extension NetworkFlutterActorImage on FlutterActorImage {
  Future<bool> changeImageFromNetwork(String url) async {
    var networkImage = NetworkImage(url);
    var val = await networkImage.obtainKey(const ImageConfiguration());
    var load = networkImage.load(val, (Uint8List bytes,
        {int cacheWidth, int cacheHeight}) {
      return PaintingBinding.instance.instantiateImageCodec(bytes,
          cacheWidth: cacheWidth, cacheHeight: cacheHeight);
    });

    final completer = Completer<bool>();
    load.addListener(ImageStreamListener((ImageInfo info, bool syncCall) {
      changeImage(info.image);
      completer.complete(true);
    }));
    return completer.future;
  }
}

You can see the example file here: https://www.2dimensions.com/a/castor/files/flare/image-swap

Note how avatar2 has Is Dynamic marked true.

Result of running the code above:

Can you share ImageSwap.flr?

There seems to be an issue with toggling "Is Dynamic" and I've filed a bug here: 2d-inc/support#255