Update test

example/lib/main.dart

@@ -1,6 +1,6 @@
-import 'package:flutter/material.dart';
 import 'dart:async';
 
+import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_usb_serial/flutter_usb_serial.dart';
 
@@ -16,34 +16,67 @@ class MyApp extends StatefulWidget {
 }
 
 class _MyAppState extends State<MyApp> {
-  String _platformVersion = 'Unknown';
-  final _flutterUsbSerialPlugin = FlutterUsbSerial();
+  List<UsbSerialDevice> _devices = const [];
+  String _status = 'Tap refresh to scan for attached USB serial devices.';
+  bool _isLoading = false;
 
   @override
   void initState() {
     super.initState();
-    initPlatformState();
+    unawaited(_refreshDevices());
   }
 
-  // Platform messages are asynchronous, so we initialize in an async method.
-  Future<void> initPlatformState() async {
-    String platformVersion;
-    // Platform messages may fail, so we use a try/catch PlatformException.
-    // We also handle the message potentially returning null.
+  Future<void> _refreshDevices() async {
+    setState(() {
+      _isLoading = true;
+    });
+
     try {
-      platformVersion =
-          await _flutterUsbSerialPlugin.getPlatformVersion() ?? 'Unknown platform version';
-    } on PlatformException {
-      platformVersion = 'Failed to get platform version.';
+      final devices = await FlutterUsbSerial.listDevices();
+      if (!mounted) return;
+      setState(() {
+        _devices = devices;
+        _status = devices.isEmpty
+            ? 'No USB serial devices detected.'
+            : 'Found ${devices.length} USB serial device(s).';
+      });
+    } on MissingPluginException {
+      if (!mounted) return;
+      setState(() {
+        _devices = const [];
+        _status = 'USB serial support is only available on Android.';
+      });
+    } on PlatformException catch (error) {
+      if (!mounted) return;
+      setState(() {
+        _devices = const [];
+        _status = error.message ?? 'Failed to list USB serial devices.';
+      });
+    } finally {
+      if (mounted) {
+        setState(() {
+          _isLoading = false;
+        });
+      }
+    }
+  }
+
+  Future<void> _requestPermission(UsbSerialDevice device) async {
+    String status;
+    try {
+      final granted = await FlutterUsbSerial.requestPermission(device);
+      status = granted
+          ? 'Permission granted for device ${device.deviceId}.'
+          : 'Permission denied for device ${device.deviceId}.';
+    } on MissingPluginException {
+      status = 'USB serial support is only available on Android.';
+    } on PlatformException catch (error) {
+      status = error.message ?? 'Failed to request USB permission.';
     }
 
-    // If the widget was removed from the tree while the asynchronous platform
-    // message was in flight, we want to discard the reply rather than calling
-    // setState to update our non-existent appearance.
     if (!mounted) return;
-
     setState(() {
-      _platformVersion = platformVersion;
+      _status = status;
     });
   }
 
@@ -52,10 +85,65 @@ class _MyAppState extends State<MyApp> {
     return MaterialApp(
       home: Scaffold(
         appBar: AppBar(
-          title: const Text('Plugin example app'),
+          title: const Text('USB Serial Example'),
         ),
-        body: Center(
-          child: Text('Running on: $_platformVersion\n'),
+        body: SafeArea(
+          child: Column(
+            children: [
+              Padding(
+                padding: const EdgeInsets.all(16),
+                child: Row(
+                  children: [
+                    Expanded(
+                      child: Text(
+                        _status,
+                        key: const Key('status_text'),
+                      ),
+                    ),
+                    const SizedBox(width: 12),
+                    FilledButton.icon(
+                      onPressed: _isLoading ? null : _refreshDevices,
+                      icon: const Icon(Icons.refresh),
+                      label: const Text('Refresh devices'),
+                    ),
+                  ],
+                ),
+              ),
+              Expanded(
+                child: _isLoading
+                    ? const Center(child: CircularProgressIndicator())
+                    : _devices.isEmpty
+                        ? const Center(
+                            child: Text('Connect an Android USB serial device to see it here.'),
+                          )
+                        : ListView.separated(
+                            itemCount: _devices.length,
+                            separatorBuilder: (_, __) => const Divider(height: 1),
+                            itemBuilder: (context, index) {
+                              final device = _devices[index];
+                              return ListTile(
+                                leading: const Icon(Icons.usb),
+                                title: Text(
+                                  device.deviceName.isEmpty
+                                      ? 'USB device ${device.deviceId}'
+                                      : device.deviceName,
+                                ),
+                                subtitle: Text(
+                                  'VID 0x${device.vendorId.toRadixString(16).padLeft(4, '0')} '
+                                  'PID 0x${device.productId.toRadixString(16).padLeft(4, '0')}\n'
+                                  'Manufacturer: ${device.manufacturerName.isEmpty ? 'Unknown' : device.manufacturerName}',
+                                ),
+                                isThreeLine: true,
+                                trailing: OutlinedButton(
+                                  onPressed: () => _requestPermission(device),
+                                  child: const Text('Request permission'),
+                                ),
+                              );
+                            },
+                          ),
+              ),
+            ],
+          ),
         ),
       ),
     );