design: Make key verification an adaptive dialog

lib/pages/key_verification/key_verification_dialog.dart

@@ -1,6 +1,7 @@
 import 'dart:convert';
 import 'dart:ui';
 
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
@@ -10,14 +11,13 @@ import 'package:future_loading_dialog/future_loading_dialog.dart';
 import 'package:matrix/encryption.dart';
 import 'package:matrix/matrix.dart';
 
-import 'package:fluffychat/utils/adaptive_bottom_sheet.dart';
 import 'package:fluffychat/widgets/avatar.dart';
 
 class KeyVerificationDialog extends StatefulWidget {
-  Future<void> show(BuildContext context) => showAdaptiveBottomSheet(
+  Future<void> show(BuildContext context) => showDialog(
         context: context,
         builder: (context) => this,
-        isDismissible: false,
+        barrierDismissible: false,
       );
 
   final KeyVerification request;
@@ -342,24 +342,32 @@ class KeyVerificationPageState extends State<KeyVerificationDialog> {
         );
         break;
     }
-    return Scaffold(
-      appBar: AppBar(
-        leading: const Center(child: CloseButton()),
+    if ({TargetPlatform.iOS, TargetPlatform.macOS}
+        .contains(Theme.of(context).platform)) {
+      return CupertinoAlertDialog(
         title: title,
-      ),
-      body: ListView(
-        padding: const EdgeInsets.all(12.0),
-        children: [body],
-      ),
-      bottomNavigationBar: SafeArea(
-        child: Padding(
-          padding: const EdgeInsets.all(12.0),
-          child: Row(
-            mainAxisAlignment: MainAxisAlignment.end,
-            children: buttons,
+        content: SizedBox(
+          height: 256,
+          width: 256,
+          child: ListView(
+            padding: const EdgeInsets.only(top: 16),
+            children: [body],
           ),
         ),
+        actions: buttons,
+      );
+    }
+
+    return AlertDialog(
+      title: title,
+      content: SizedBox(
+        height: 256,
+        width: 256,
+        child: ListView(
+          children: [body],
+        ),
       ),
+      actions: buttons,
     );
   }
 }