use alertDialog.adaptive and _adaptiveWidget to user Cupertino flavour for ios

Author: u7088495

lib/widgets/dialog.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_gen/gen_l10n/zulip_localizations.dart';
+import 'package:flutter/cupertino.dart';
 
 Widget _dialogActionText(String text) {
   return Text(
@@ -15,6 +16,30 @@ Widget _dialogActionText(String text) {
   );
 }
 
+// Sets the dialog action to be platform appropriate
+// by displaying a [CupertinoDialogAction] for IOS platforms
+// and a regular [TextButton] otherwise.
+Widget _adaptiveAction(
+      {required BuildContext context,
+      required VoidCallback onPressed,
+      required Widget child}) {
+    final ThemeData theme = Theme.of(context);
+    switch (theme.platform) {
+      case TargetPlatform.android:
+        return TextButton(onPressed: onPressed, child: child);
+      case TargetPlatform.fuchsia:
+      return TextButton(onPressed: onPressed, child: child);
+      case TargetPlatform.linux:
+        return TextButton(onPressed: onPressed, child: child);
+      case TargetPlatform.windows:
+        return TextButton(onPressed: onPressed, child: child);
+      case TargetPlatform.iOS:
+        return CupertinoDialogAction(onPressed: onPressed, child: child);
+      case TargetPlatform.macOS:
+        return CupertinoDialogAction(onPressed: onPressed, child: child);
+    }
+  }
+
 /// Tracks the status of a dialog, in being still open or already closed.
 ///
 /// See also:
@@ -42,11 +67,12 @@ DialogStatus showErrorDialog({
   final zulipLocalizations = ZulipLocalizations.of(context);
   final future = showDialog<void>(
     context: context,
-    builder: (BuildContext context) => AlertDialog(
+    builder: (BuildContext context) => AlertDialog.adaptive(
       title: Text(title),
       content: message != null ? SingleChildScrollView(child: Text(message)) : null,
       actions: [
-        TextButton(
+        _adaptiveAction(
+          context: context,
           onPressed: () => Navigator.pop(context),
           child: _dialogActionText(zulipLocalizations.errorDialogContinue)),
       ]));
@@ -63,14 +89,16 @@ void showSuggestedActionDialog({
   final zulipLocalizations = ZulipLocalizations.of(context);
   showDialog<void>(
     context: context,
-    builder: (BuildContext context) => AlertDialog(
+    builder: (BuildContext context) => AlertDialog.adaptive(
       title: Text(title),
       content: SingleChildScrollView(child: Text(message)),
       actions: [
-        TextButton(
+        _adaptiveAction(
+          context: context,
           onPressed: () => Navigator.pop(context),
           child: _dialogActionText(zulipLocalizations.dialogCancel)),
-        TextButton(
+        _adaptiveAction(
+          context: context,
           onPressed: onActionButtonPress,
           child: _dialogActionText(actionButtonText ?? zulipLocalizations.dialogContinue)),
       ]));