fix: make the moxxmpp example work again

Note: to do this, I could not use the ExampleTcpSocketWrapper.
If I did, the app crashed on launch.

I also added some functionality: the header bar turns green when
connected, the FAB says what it does, and you can disconnect.

Signed-off-by: Blake Leonard <me@blakes.dev>

example/lib/main.dart

@@ -55,21 +55,25 @@ class MyHomePage extends StatefulWidget {
 
 class _MyHomePageState extends State<MyHomePage> {
   final XmppConnection connection = XmppConnection(
-    ExponentialBackoffReconnectionPolicy(),
+    RandomBackoffReconnectionPolicy(1, 60),
-    ExampleTcpSocketWrapper(),
+    AlwaysConnectedConnectivityManager(),
+    //ExampleTcpSocketWrapper(), // this causes the app to crash
+    TCPSocketWrapper(true), // Note: you probably want this to be false in a real app
   );
   TextEditingController jidController = TextEditingController();
   TextEditingController passwordController = TextEditingController();
+  bool connected = false;
+  bool loading = false;
 
   _MyHomePageState() : super() {
     connection
       ..registerManagers([
         StreamManagementManager(),
-        DiscoManager(),
+        DiscoManager([]),
-        RosterManager(),
+        RosterManager(TestingRosterStateManager("", [])),
         PingManager(),
         MessageManager(),
-        PresenceManager('http://moxxmpp.example'),
+        PresenceManager(),
       ])
       ..registerFeatureNegotiators([
         ResourceBindingNegotiator(),
@@ -85,15 +89,24 @@ class _MyHomePageState extends State<MyHomePage> {
   }
   
   Future<void> _buttonPressed() async {
+    if (connected) {
+      await connection.disconnect();
+      setState(() {connected = false;});
+      return;
+    }
+    setState(() {loading = true;});
     connection.setConnectionSettings(
       ConnectionSettings(
         jid: JID.fromString(jidController.text),
         password: passwordController.text,
         useDirectTLS: true,
         allowPlainAuth: false,
+          // otherwise, connecting to some servers will
+          // cause an app to hang
       ),
     );
     await connection.connect();
+    setState(() {connected = true; loading = false;});
   }
 
   @override
@@ -101,18 +114,22 @@ class _MyHomePageState extends State<MyHomePage> {
     return Scaffold(
       appBar: AppBar(
         title: Text(widget.title),
+        backgroundColor: connected ? Colors.green : Colors.deepPurple[800],
+        foregroundColor: connected ? Colors.black : Colors.white,
       ),
       body: Center(
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
             TextField(
+              enabled: !loading,
               controller: jidController,
               decoration: InputDecoration(
                 labelText: 'JID',
               ),
             ),
             TextField(
+              enabled: !loading,
               controller: passwordController,
               decoration: InputDecoration(
                 labelText: 'Password',
@@ -122,10 +139,13 @@ class _MyHomePageState extends State<MyHomePage> {
           ],
         ),
       ),
-      floatingActionButton: FloatingActionButton(
+      floatingActionButton: FloatingActionButton.extended(
         onPressed: _buttonPressed,
+        label: Text(connected ? 'Disconnect' : 'Connect'),
+        backgroundColor: Colors.blue,
+        foregroundColor: Colors.white,
         tooltip: 'Connect',
-        child: const Icon(Icons.add),
+        icon: const Icon(Icons.power),
       ),
     );
   }