Adds onStateChange callback

CHANGELOG.md

@@ -1,8 +1,13 @@
+## [0.7.21] - 2021-06-21 14:00:00
+- Adds onStateChange callback to state machine controllers
+
 ## [0.7.20] - 2021-06-19 19:01:10
-- Quick start fixes in README.md.
+- Quick start fixes in README.md
+
 ## [0.7.19] - 2021-06-18 12:00:00
 - BREAKING CHANGE: onInit callback now takes an artboard as a parameter
 - Adds simple state machine example
+
 ## [0.7.18] - 2021-06-14 12:00:00
 - Adds ability to pass controllers into RiveAnimation widgets
 - Adds autoplay option to SimpleAnimation controller

README.md

@@ -8,7 +8,7 @@ Runtime docs are available in [Rive's help center](https://help.rive.app/runtime
 
 ```yaml
 dependencies:
-  rive: ^0.7.20
+  rive: ^0.7.21
 ```
 
 ## Quick Start

example/lib/little_machine.dart

@@ -15,6 +15,9 @@ class _LittleMachineState extends State<LittleMachine> {
   /// Tracks if the animation is playing by whether controller is running.
   bool get isPlaying => _controller?.isActive ?? false;
 
+  /// Message that displays when state has changed
+  String stateChangeMessage = '';
+
   Artboard? _riveArtboard;
   StateMachineController? _controller;
   SMIInput<bool>? _trigger;
@@ -33,8 +36,11 @@ class _LittleMachineState extends State<LittleMachine> {
         // The artboard is the root of the animation and gets drawn in the
         // Rive widget.
         final artboard = file.mainArtboard;
-        var controller =
-            StateMachineController.fromArtboard(artboard, 'State Machine 1');
+        var controller = StateMachineController.fromArtboard(
+          artboard,
+          'State Machine 1',
+          onStateChange: _onStateChange,
+        );
         if (controller != null) {
           artboard.addController(controller);
           _trigger = controller.findInput('Trigger 1');
@@ -44,6 +50,12 @@ class _LittleMachineState extends State<LittleMachine> {
     );
   }
 
+  /// Do something when the state machine changes state
+  void _onStateChange(String stateMachineName, String stateName) => setState(
+        () => stateChangeMessage =
+            'State Changed in $stateMachineName to $stateName',
+      );
+
   @override
   Widget build(BuildContext context) {
     return Scaffold(
@@ -71,6 +83,9 @@ class _LittleMachineState extends State<LittleMachine> {
                         artboard: _riveArtboard!,
                       ),
                     ),
+                    const SizedBox(height: 10),
+                    Text('$stateChangeMessage'),
+                    const SizedBox(height: 10),
                   ],
                 ),
               ),

lib/src/controllers/state_machine_controller.dart

@@ -119,7 +119,10 @@ class StateMachineController extends core.StateMachineController {
   /// A list of inputs available in the StateMachine.
   Iterable<SMIInput> get inputs => _inputs;
 
-  StateMachineController(StateMachine stateMachine) : super(stateMachine) {
+  StateMachineController(
+    StateMachine stateMachine, {
+    core.OnStateChange? onStateChange,
+  }) : super(stateMachine, onStateChange: onStateChange) {
     isActive = true;
     for (final input in stateMachine.inputs) {
       switch (input.coreType) {
@@ -140,10 +143,13 @@ class StateMachineController extends core.StateMachineController {
   /// [stateMachineName]. Returns the [StateMachineController] or null if no
   /// [StateMachine] with [stateMachineName] is found.
   static StateMachineController? fromArtboard(
-      Artboard artboard, String stateMachineName) {
+    Artboard artboard,
+    String stateMachineName, {
+    core.OnStateChange? onStateChange,
+  }) {
     for (final animation in artboard.animations) {
       if (animation is StateMachine && animation.name == stateMachineName) {
-        return StateMachineController(animation);
+        return StateMachineController(animation, onStateChange: onStateChange);
       }
     }
     return null;

lib/src/rive_core/state_machine_controller.dart

@@ -1,5 +1,6 @@
 import 'dart:collection';
 
+import 'package:flutter/scheduler.dart';
 import 'package:rive/src/core/core.dart';
 import 'package:flutter/foundation.dart';
 import 'package:rive/src/rive_core/animation/animation_state_instance.dart';
@@ -12,6 +13,16 @@ import 'package:rive/src/rive_core/animation/state_machine_layer.dart';
 import 'package:rive/src/rive_core/animation/state_transition.dart';
 import 'package:rive/src/rive_core/rive_animation_controller.dart';
 
+import 'animation/animation_state.dart';
+import 'animation/entry_state.dart';
+import 'animation/exit_state.dart';
+
+/// Callback signature for satate machine state changes
+typedef OnStateChange = void Function(String, String);
+
+/// Callback signature for layer state changes
+typedef OnLayerStateChange = void Function(LayerState);
+
 class LayerController {
   final StateMachineLayer layer;
   final StateInstance anyStateInstance;
@@ -23,7 +34,11 @@ class LayerController {
   double _mix = 1.0;
   double _mixFrom = 1.0;
 
-  LayerController(this.layer)
+  /// Optional callback which is called when a state changes
+  /// Takes the state machine name and state name
+  final OnLayerStateChange? onLayerStateChange;
+
+  LayerController(this.layer, {this.onLayerStateChange})
       : assert(layer.anyState != null),
         anyStateInstance = layer.anyState!.makeInstance() {
     _changeState(layer.entryState);
@@ -167,6 +182,10 @@ class LayerController {
         // Make sure to reset _waitingForExit to false if we succeed at taking a
         // transition.
         _waitingForExit = false;
+        // State has changed, fire the callback if there's one
+        if (_currentState != null) {
+          onLayerStateChange?.call(_currentState!.state);
+        }
         return true;
       } else if (allowed == AllowTransition.waitingForExit) {
         _waitingForExit = true;
@@ -179,9 +198,14 @@ class LayerController {
 class StateMachineController extends RiveAnimationController<CoreContext> {
   final StateMachine stateMachine;
   final inputValues = HashMap<int, dynamic>();
-  StateMachineController(this.stateMachine);
   final layerControllers = <LayerController>[];
 
+  /// Optional callback for state changes
+  final OnStateChange? onStateChange;
+
+  /// Constructor that takes a state machine and optional state change callback
+  StateMachineController(this.stateMachine, {this.onStateChange});
+
   void _clearLayerControllers() {
     for (final layer in layerControllers) {
       layer.dispose();
@@ -189,12 +213,33 @@ class StateMachineController extends RiveAnimationController<CoreContext> {
     layerControllers.clear();
   }
 
+  /// Handles state change callbacks
+  void _onStateChange(LayerState layerState) =>
+      SchedulerBinding.instance?.addPostFrameCallback((_) {
+        String stateName = 'unknown';
+        print('Layer state type ${layerState.runtimeType}');
+        if (layerState is AnimationState && layerState.animation != null) {
+          stateName = layerState.animation!.name;
+        } else if (layerState is EntryState) {
+          stateName = 'EntryState';
+        } else if (layerState is AnyState) {
+          stateName = 'EntryState';
+        } else if (layerState is ExitState) {
+          stateName = 'ExitState';
+        }
+
+        onStateChange?.call(stateMachine.name, stateName);
+      });
+
   @override
   bool init(CoreContext core) {
     _clearLayerControllers();
 
     for (final layer in stateMachine.layers) {
-      layerControllers.add(LayerController(layer));
+      layerControllers.add(LayerController(
+        layer,
+        onLayerStateChange: _onStateChange,
+      ));
     }
 
     // Make sure triggers are all reset.