Fix data channel not work issue

Need set local description when recevie offer event. copy code from
call_sample.dart

Author: xiaowei-guan

lib/src/call_sample/call_sample.dart

@@ -186,7 +186,7 @@ class _CallSampleState extends State<CallSample> {
 
   _accept() {
     if (_session != null) {
-      _signaling?.accept(_session!.sid);
+      _signaling?.accept(_session!.sid, 'video');
     }
   }
 

lib/src/call_sample/data_channel_sample.dart

@@ -25,6 +25,7 @@ class _DataChannelSampleState extends State<DataChannelSample> {
   var _text = '';
   // ignore: unused_element
   _DataChannelSampleState();
+  bool _waitAccept = false;
 
   @override
   initState() {
@@ -39,6 +40,55 @@ class _DataChannelSampleState extends State<DataChannelSample> {
     _timer?.cancel();
   }
 
+  Future<bool?> _showAcceptDialog() {
+    return showDialog<bool?>(
+      context: context,
+      builder: (context) {
+        return AlertDialog(
+          title: Text("title"),
+          content: Text("accept?"),
+          actions: <Widget>[
+            MaterialButton(
+              child: Text(
+                'Reject',
+                style: TextStyle(color: Colors.red),
+              ),
+              onPressed: () => Navigator.of(context).pop(false),
+            ),
+            MaterialButton(
+              child: Text(
+                'Accept',
+                style: TextStyle(color: Colors.green),
+              ),
+              onPressed: () => Navigator.of(context).pop(true),
+            ),
+          ],
+        );
+      },
+    );
+  }
+
+  Future<bool?> _showInvateDialog() {
+    return showDialog<bool?>(
+      context: context,
+      builder: (context) {
+        return AlertDialog(
+          title: Text("title"),
+          content: Text("waiting"),
+          actions: <Widget>[
+            TextButton(
+              child: Text("cancel"),
+              onPressed: () {
+                Navigator.of(context).pop(false);
+                _hangUp();
+              },
+            ),
+          ],
+        );
+      },
+    );
+  }
+
   void _connect(BuildContext context) async {
     _signaling ??= Signaling(widget.host, context)..connect();
 
@@ -65,33 +115,54 @@ class _DataChannelSampleState extends State<DataChannelSample> {
       }
     };
 
-    _signaling?.onCallStateChange = (Session session, CallState state) {
+    _signaling?.onCallStateChange = (Session session, CallState state) async {
       switch (state) {
         case CallState.CallStateNew:
-          {
-            setState(() {
-              _session = session;
-              _inCalling = true;
-            });
-            _timer =
-                Timer.periodic(Duration(seconds: 1), _handleDataChannelTest);
-            break;
-          }
+          setState(() {
+            _session = session;
+          });
+          _timer = Timer.periodic(Duration(seconds: 1), _handleDataChannelTest);
+          break;
         case CallState.CallStateBye:
-          {
-            setState(() {
-              _inCalling = false;
-            });
-            _timer?.cancel();
-            _dataChannel = null;
-            _inCalling = false;
-            _session = null;
-            _text = '';
-            break;
+          if (_waitAccept) {
+            print('peer reject');
+            _waitAccept = false;
+            Navigator.of(context).pop(false);
           }
+          setState(() {
+            _inCalling = false;
+          });
+          _timer?.cancel();
+          _dataChannel = null;
+          _inCalling = false;
+          _session = null;
+          _text = '';
+          break;
         case CallState.CallStateInvite:
+          _waitAccept = true;
+          _showInvateDialog();
+          break;
         case CallState.CallStateConnected:
+          if (_waitAccept) {
+            _waitAccept = false;
+            Navigator.of(context).pop(false);
+          }
+          setState(() {
+            _inCalling = true;
+          });
+          break;
         case CallState.CallStateRinging:
+          bool? accept = await _showAcceptDialog();
+          if (accept!) {
+            _accept();
+            setState(() {
+              _inCalling = true;
+            });
+          } else {
+            _reject();
+          }
+
+          break;
       }
     };
 
@@ -117,6 +188,18 @@ class _DataChannelSampleState extends State<DataChannelSample> {
     }
   }
 
+  _accept() {
+    if (_session != null) {
+      _signaling?.accept(_session!.sid, 'data');
+    }
+  }
+
+  _reject() {
+    if (_session != null) {
+      _signaling?.reject(_session!.sid);
+    }
+  }
+
   _hangUp() {
     _signaling?.bye(_session!.sid);
   }

lib/src/call_sample/signaling.dart

@@ -165,12 +165,12 @@ class Signaling {
     }
   }
 
-  void accept(String sessionId) {
+  void accept(String sessionId, String media) {
     var session = _sessions[sessionId];
     if (session == null) {
       return;
     }
-    _createAnswer(session, 'video');
+    _createAnswer(session, media);
   }
 
   void reject(String sessionId) {