update animation methods to return futures

mobile/lib/widgets/photo_view/src/controller/photo_view_controller.dart

@@ -38,12 +38,13 @@ abstract class PhotoViewControllerBase<T extends PhotoViewControllerValue> {
   /// Closes streams and removes eventual listeners.
   void dispose();
 
-  void positionAnimationBuilder(void Function(Offset)? value);
+  void positionAnimationBuilder(Future<void> Function(Offset)? value);
-  void scaleAnimationBuilder(void Function(double)? value);
+  void scaleAnimationBuilder(Future<void> Function(double)? value);
-  void rotationAnimationBuilder(void Function(double)? value);
+  void rotationAnimationBuilder(Future<void> Function(double)? value);
 
-  /// Animates multiple fields of the state
+  /// Animates multiple fields of the state. The returned future completes
-  void animateMultiple({Offset? position, double? scale, double? rotation});
+  /// when all underlying animations have settled.
+  Future<void> animateMultiple({Offset? position, double? scale, double? rotation});
 
   /// Add a listener that will ignore updates made internally
   ///
@@ -148,9 +149,9 @@ class PhotoViewController implements PhotoViewControllerBase<PhotoViewController
   @override
   ScaleBoundaries? scaleBoundaries;
 
-  late void Function(Offset)? _animatePosition;
+  late Future<void> Function(Offset)? _animatePosition;
-  late void Function(double)? _animateScale;
+  late Future<void> Function(double)? _animateScale;
-  late void Function(double)? _animateRotation;
+  late Future<void> Function(double)? _animateRotation;
 
   @override
   Stream<PhotoViewControllerValue> get outputStateStream => _outputCtrl.stream;
@@ -159,17 +160,17 @@ class PhotoViewController implements PhotoViewControllerBase<PhotoViewController
   late PhotoViewControllerValue prevValue;
 
   @override
-  void positionAnimationBuilder(void Function(Offset)? value) {
+  void positionAnimationBuilder(Future<void> Function(Offset)? value) {
     _animatePosition = value;
   }
 
   @override
-  void scaleAnimationBuilder(void Function(double)? value) {
+  void scaleAnimationBuilder(Future<void> Function(double)? value) {
     _animateScale = value;
   }
 
   @override
-  void rotationAnimationBuilder(void Function(double)? value) {
+  void rotationAnimationBuilder(Future<void> Function(double)? value) {
     _animateRotation = value;
   }
 
@@ -193,18 +194,18 @@ class PhotoViewController implements PhotoViewControllerBase<PhotoViewController
   }
 
   @override
-  void animateMultiple({Offset? position, double? scale, double? rotation}) {
+  Future<void> animateMultiple({Offset? position, double? scale, double? rotation}) {
+    final futures = <Future<void>>[];
     if (position != null && _animatePosition != null) {
-      _animatePosition!(position);
+      futures.add(_animatePosition!(position));
     }
-
     if (scale != null && _animateScale != null) {
-      _animateScale!(scale);
+      futures.add(_animateScale!(scale));
     }
-
     if (rotation != null && _animateRotation != null) {
-      _animateRotation!(rotation);
+      futures.add(_animateRotation!(rotation));
     }
+    return Future.wait(futures);
   }
 
   @override

mobile/lib/widgets/photo_view/src/core/photo_view_core.dart

@@ -237,34 +237,31 @@ class PhotoViewCoreState extends State<PhotoViewCore>
     nextScaleState();
   }
 
-  void animateScale(double from, double to) {
+  Future<void> animateScale(double from, double to) {
     if (!mounted) {
-      return;
+      return Future.value();
     }
     _scaleAnimation = Tween<double>(begin: from, end: to).animate(_scaleAnimationController);
-    _scaleAnimationController
+    _scaleAnimationController.value = 0.0;
-      ..value = 0.0
+    return _scaleAnimationController.fling(velocity: 0.4);
-      ..fling(velocity: 0.4);
   }
 
-  void animatePosition(Offset from, Offset to) {
+  Future<void> animatePosition(Offset from, Offset to) {
     if (!mounted) {
-      return;
+      return Future.value();
     }
     _positionAnimation = Tween<Offset>(begin: from, end: to).animate(_positionAnimationController);
-    _positionAnimationController
+    _positionAnimationController.value = 0.0;
-      ..value = 0.0
+    return _positionAnimationController.fling(velocity: 0.4);
-      ..fling(velocity: 0.4);
   }
 
-  void animateRotation(double from, double to) {
+  Future<void> animateRotation(double from, double to) {
     if (!mounted) {
-      return;
+      return Future.value();
     }
     _rotationAnimation = Tween<double>(begin: from, end: to).animate(_rotationAnimationController);
-    _rotationAnimationController
+    _rotationAnimationController.value = 0.0;
-      ..value = 0.0
+    return _rotationAnimationController.fling(velocity: 0.4);
-      ..fling(velocity: 0.4);
   }
 
   void onAnimationStatus(AnimationStatus status) {
@@ -280,18 +277,19 @@ class PhotoViewCoreState extends State<PhotoViewCore>
     }
   }
 
-  void _animateControllerPosition(Offset position) {
+  Future<void> _animateControllerPosition(Offset position) {
-    animatePosition(controller.position, position);
+    return animatePosition(controller.position, position);
   }
 
-  void _animateControllerScale(double scale) {
+  Future<void> _animateControllerScale(double scale) {
     if (controller.scale != null) {
-      animateScale(controller.scale!, scale);
+      return animateScale(controller.scale!, scale);
     }
+    return Future.value();
   }
 
-  void _animateControllerRotation(double rotation) {
+  Future<void> _animateControllerRotation(double rotation) {
-    animateRotation(controller.rotation, rotation);
+    return animateRotation(controller.rotation, rotation);
   }
 
   @override