flutter: Change new game from AlertDialog to SimpleDialog

src/ui/flutter_app/lib/l10n/intl_zh.arb

@@ -33,7 +33,7 @@
   "draw": "和棋",
   "thinking": "对方思考中...",
   "newGame": "新局",
-  "startNewGame": "重新开局",
+  "startNewGame": "开始新局",
   "restartGame": "重新开局？",
   "restart": "重开局",
   "gameStarted": "游戏开始 请落子",

src/ui/flutter_app/lib/style/app_theme.dart

@@ -26,6 +26,7 @@ class AppTheme {
   static var moveHistoryDialogBackgroundColor = Colors.transparent;
   static var hintDialogackgroundColor = moveHistoryDialogBackgroundColor;
   static var hintTextColor = moveHistoryTextColor;
+  static var simpleDialogOptionTextColor = appPrimaryColor;
 
   /// Settings page
   static var darkBackgroundColor = UIColors.crusoe;
@@ -99,9 +100,15 @@ class AppTheme {
     fontWeight: FontWeight.w600,
   );
 
+  static var simpleDialogOptionTextStyle = TextStyle(
+    fontSize: AppTheme.simpleDialogOptionFontSize,
+    color: AppTheme.simpleDialogOptionTextColor,
+  );
+
   static var moveHistoryTextStyle =
       TextStyle(fontSize: 18, height: 1.5, color: moveHistoryTextColor);
 
+  static double simpleDialogOptionFontSize = 20.0;
   static double gamePageTopMargin = 28.0;
   static double boardMargin = 10.0;
   static double boardScreenPaddingH = 10.0;

src/ui/flutter_app/lib/widgets/game_page.dart

@@ -323,14 +323,14 @@ class _GamePageState extends State<GamePage> with RouteAware {
     showDialog(
       context: context,
       builder: (BuildContext context) {
-        return AlertDialog(
-          title: Text(S.of(context).newGame,
-              style: TextStyle(color: AppTheme.dialogTitleColor)),
-          content:
-              SingleChildScrollView(child: Text(S.of(context).restartGame)),
-          actions: <Widget>[
-            TextButton(child: Text(S.of(context).restart), onPressed: confirm),
-            TextButton(child: Text(S.of(context).cancel), onPressed: cancel),
+        return SimpleDialog(
+          children: <Widget>[
+            SimpleDialogOption(
+                child: Text(
+                  S.of(context).startNewGame,
+                  style: AppTheme.simpleDialogOptionTextStyle,
+                ),
+                onPressed: confirm),
           ],
         );
       },