Fixes touch handling in SpriteBox

packages/flutter_sprites/lib/flutter_sprites.dart

@@ -14,6 +14,7 @@ import 'package:box2d/box2d.dart' as box2d;
 import 'package:mojo/core.dart';
 import 'package:sky_services/media/media.mojom.dart';
 import 'package:flutter/animation.dart';
+import 'package:flutter/gestures.dart';
 import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';

packages/flutter_sprites/lib/src/sprite_box.dart

@@ -185,11 +185,11 @@ class SpriteBox extends RenderBox {
     }
   }
 
-  void handleEvent(ui.Event event, _SpriteBoxHitTestEntry entry) {
+  void handleEvent(InputEvent event, _SpriteBoxHitTestEntry entry) {
     if (!attached)
       return;
 
-    if (event is ui.PointerEvent) {
+    if (event is PointerInputEvent) {
 
       if (event.type == 'pointerdown') {
         // Build list of event targets