Add game_template (#1180)

Adds a template / sample for games built in Flutter, with all the bells and whistles, like ads, in-app purchases, audio, main menu, settings, and so on.

Co-authored-by: Parker Lougheed
Co-authored-by: Shams Zakhour

game_template/lib/src/games_services/games_services.dart

@@ -0,0 +1,119 @@
+// Copyright 2022, the Flutter project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:games_services/games_services.dart' as gs;
+import 'package:logging/logging.dart';
+
+import 'score.dart';
+
+/// Allows awarding achievements and leaderboard scores,
+/// and also showing the platforms' UI overlays for achievements
+/// and leaderboards.
+///
+/// A facade of `package:games_services`.
+class GamesServicesController {
+  static final Logger _log = Logger('GamesServicesController');
+
+  final Completer<bool> _signedInCompleter = Completer();
+
+  Future<bool> get signedIn => _signedInCompleter.future;
+
+  /// Unlocks an achievement on Game Center / Play Games.
+  ///
+  /// You must provide the achievement ids via the [iOS] and [android]
+  /// parameters.
+  ///
+  /// Does nothing when the game isn't signed into the underlying
+  /// games service.
+  Future<void> awardAchievement(
+      {required String iOS, required String android}) async {
+    if (!await signedIn) {
+      _log.warning('Trying to award achievement when not logged in.');
+      return;
+    }
+
+    try {
+      await gs.GamesServices.unlock(
+        achievement: gs.Achievement(
+          androidID: android,
+          iOSID: iOS,
+        ),
+      );
+    } catch (e) {
+      _log.severe('Cannot award achievement: $e');
+    }
+  }
+
+  /// Signs into the underlying games service.
+  Future<void> initialize() async {
+    try {
+      await gs.GamesServices.signIn();
+      // The API is unclear so we're checking to be sure. The above call
+      // returns a String, not a boolean, and there's no documentation
+      // as to whether every non-error result means we're safely signed in.
+      final signedIn = await gs.GamesServices.isSignedIn;
+      _signedInCompleter.complete(signedIn);
+    } catch (e) {
+      _log.severe('Cannot log into GamesServices: $e');
+      _signedInCompleter.complete(false);
+    }
+  }
+
+  /// Launches the platform's UI overlay with achievements.
+  Future<void> showAchievements() async {
+    if (!await signedIn) {
+      _log.severe('Trying to show achievements when not logged in.');
+      return;
+    }
+
+    try {
+      await gs.GamesServices.showAchievements();
+    } catch (e) {
+      _log.severe('Cannot show achievements: $e');
+    }
+  }
+
+  /// Launches the platform's UI overlay with leaderboard(s).
+  Future<void> showLeaderboard() async {
+    if (!await signedIn) {
+      _log.severe('Trying to show leaderboard when not logged in.');
+      return;
+    }
+
+    try {
+      await gs.GamesServices.showLeaderboards(
+        // TODO: When ready, change both these leaderboard IDs.
+        iOSLeaderboardID: "some_id_from_app_store",
+        androidLeaderboardID: "sOmE_iD_fRoM_gPlAy",
+      );
+    } catch (e) {
+      _log.severe('Cannot show leaderboard: $e');
+    }
+  }
+
+  /// Submits [score] to the leaderboard.
+  Future<void> submitLeaderboardScore(Score score) async {
+    if (!await signedIn) {
+      _log.warning('Trying to submit leaderboard when not logged in.');
+      return;
+    }
+
+    _log.info('Submitting $score to leaderboard.');
+
+    try {
+      await gs.GamesServices.submitScore(
+        score: gs.Score(
+          // TODO: When ready, change these leaderboard IDs.
+          iOSLeaderboardID: 'some_id_from_app_store',
+          androidLeaderboardID: 'sOmE_iD_fRoM_gPlAy',
+          value: score.score,
+        ),
+      );
+    } catch (e) {
+      _log.severe('Cannot submit leaderboard score: $e');
+    }
+  }
+}