Adds custom controller for speed example

example/lib/custom_controller.dart

@@ -0,0 +1,57 @@
+/// Demonstrates how to create a custom controller to change the speed of an
+/// animation
+
+import 'package:flutter/material.dart';
+import 'package:rive/rive.dart';
+
+class SpeedyAnimation extends StatelessWidget {
+  const SpeedyAnimation({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Custom Controller'),
+      ),
+      body: Center(
+        child: RiveAnimation.network(
+          'https://cdn.rive.app/animations/vehicles.riv',
+          fit: BoxFit.cover,
+          animations: const ['idle'],
+          controllers: [SpeedController('curves', speedMultiplier: 3)],
+        ),
+      ),
+    );
+  }
+}
+
+class SpeedController extends SimpleAnimation {
+  final double speedMultiplier;
+
+  /// Stops the animation on the next apply
+  bool _stopOnNextApply = false;
+
+  SpeedController(
+    String animationName, {
+    double mix = 1,
+    this.speedMultiplier = 1,
+  }) : super(
+          animationName,
+          mix: mix,
+        );
+
+  @override
+  void apply(RuntimeArtboard artboard, double elapsedSeconds) {
+    if (_stopOnNextApply || instance == null) {
+      isActive = false;
+    }
+
+    instance!.animation.apply(instance!.time, coreContext: artboard, mix: mix);
+    if (!instance!.advance(elapsedSeconds * speedMultiplier)) {
+      _stopOnNextApply = true;
+    }
+  }
+
+  @override
+  void onActivate() => _stopOnNextApply = false;
+}

example/lib/main.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:rive_example/custom_controller.dart';
 import 'package:rive_example/play_one_shot_animation.dart';
 import 'package:rive_example/play_pause_animation.dart';
 import 'package:rive_example/example_state_machine.dart';
@@ -118,6 +119,20 @@ class Home extends StatelessWidget {
                 );
               },
             ),
+            const SizedBox(
+              height: 10,
+            ),
+            ElevatedButton(
+              child: const Text('Custom Controller - Speed'),
+              onPressed: () {
+                Navigator.push(
+                  context,
+                  MaterialPageRoute<void>(
+                    builder: (context) => const SpeedyAnimation(),
+                  ),
+                );
+              },
+            ),
           ],
         ),
       ),