fix: Hardcode initCurrentGame lifecycle state as resumed (#2775)

When the init game method is called straight after the app has launched, the lifecycle state from WidgetsBinding.instance.lifecycleState often returns disposed or inactive which causes the engine to stay paused even though the app is foregrounded.
This PR fixes the lifecycle state as resumed when the init method is called.

packages/flame/lib/src/game/game_widget/game_widget.dart

@@ -253,13 +253,24 @@ class GameWidgetState<T extends Game> extends State<GameWidget<T>> {
     } else {
       currentGame = widget.game!;
     }
-    currentGame.addGameStateListener(_onGameStateChange);
-    currentGame.lifecycleStateChange(
-      WidgetsBinding.instance.lifecycleState ?? AppLifecycleState.resumed,
-    );
+    initGameStateListener(currentGame, _onGameStateChange);
     _loaderFuture = null;
   }
 
+  /// Visible for testing for
+  /// https://github.com/flame-engine/flame/issues/2771.
+  @visibleForTesting
+  static void initGameStateListener(
+    Game currentGame,
+    void Function() onGameStateChange,
+  ) {
+    currentGame.addGameStateListener(onGameStateChange);
+
+    // See https://github.com/flame-engine/flame/issues/2771
+    // for why we aren't using [WidgetsBinding.instance.lifecycleState].
+    currentGame.lifecycleStateChange(AppLifecycleState.resumed);
+  }
+
   /// [disposeCurrentGame] is called by two flutter events - `didUpdateWidget`
   /// and `dispose`.  When the parameter [callGameOnDispose] is true, the
   /// `currentGame`'s `onDispose` method will be called; otherwise, it will not.

packages/flame/test/game/flame_game_test.dart

@@ -720,21 +720,37 @@ void main() {
         expect(game.paused, isFalse);
       });
 
-      testWidgets(
-        'game is not paused on start',
-        (tester) async {
-          final game = FlameGame();
-
-          await tester.pumpWidget(
-            GameWidget(game: game),
-          );
-
-          await game.toBeLoaded();
-          await tester.pump();
-
-          expect(game.paused, isFalse);
-        },
-      );
+      for (final startingLifecycleState in AppLifecycleState.values) {
+        testWidgets(
+          'game is not paused on start when initially $startingLifecycleState',
+          (tester) async {
+            WidgetsBinding.instance.handleAppLifecycleStateChanged(
+              startingLifecycleState,
+            );
+            addTearDown(() {
+              // Don't use [WidgetsBinding.instance.resetLifecycleState()]
+              // because it sets the lifecycle to null which prevents
+              // [game.onLoad] from running in other tests.
+              WidgetsBinding.instance.handleAppLifecycleStateChanged(
+                AppLifecycleState.resumed,
+              );
+            });
+            expect(
+              WidgetsBinding.instance.lifecycleState,
+              startingLifecycleState,
+            );
+
+            final game = FlameGame();
+
+            final gameWidget = GameWidget(game: game);
+            await tester.pumpWidget(gameWidget);
+
+            GameWidgetState.initGameStateListener(game, () {});
+
+            expect(game.paused, isFalse);
+          },
+        );
+      }
 
       testWidgets(
         'game is paused when app is backgrounded',