Flutter_blue: How to handle errors

[FWeissenb]

I tried to catch a Timeout Exception from FlutterBlue connect. But it doesn't work.

I tried:

try {
      await scanResult.device.connect(timeout: Duration(seconds: 5));
    } on TimeoutException catch (e) {
      print(debugPrefix + " $e");
    }

And I tried

await r.device.connect(timeout: Duration(seconds: 5)).catchError((e){

       print(debugPrefix + " $e");

     });

All I get is the message in debug console and my app stops :/

E/flutter (11807): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: TimeoutException after 0:00:05.000000: Failed to connect in time.
E/flutter (11807): #0      BluetoothDevice.connect.<anonymous closure> 
package:flutter_blue/src/bluetooth_device.dart:33
E/flutter (11807): #1      _rootRun  (dart:async/zone.dart:1120:38)
E/flutter (11807): #2      _CustomZone.run  (dart:async/zone.dart:1021:19)
E/flutter (11807): #3      _CustomZone.runGuarded  (dart:async/zone.dart:923:7)
E/flutter (11807): #4      _CustomZone.bindCallbackGuarded.<anonymous closure>  (dart:async/zone.dart:963:23)
E/flutter (11807): #5      _rootRun  (dart:async/zone.dart:1124:13)
E/flutter (11807): #6      _CustomZone.run  (dart:async/zone.dart:1021:19)
E/flutter (11807): #7      _CustomZone.bindCallback.<anonymous closure>  (dart:async/zone.dart:947:23)
E/flutter (11807): #8      Timer._createTimer.<anonymous closure>  (dart:async-patch/timer_patch.dart:21:15)
E/flutter (11807): #9      _Timer._runTimers  (dart:isolate-patch/timer_impl.dart:382:19)
E/flutter (11807): #10     _Timer._handleMessage  (dart:isolate-patch/timer_impl.dart:416:5)
E/flutter (11807): #11     _RawReceivePortImpl._handleMessage  (dart:isolate-patch/isolate_patch.dart:171:12)

Is this a flutterblue, a dart or a user problem?

[FWeissenb]

if I handle it this way

runZoned(() async {
      await r.device.connect(timeout: Duration(seconds: 5), autoConnect: false);
    }, onError: (e){
              print(debugPrefix + " Error: $e");
          error = true;
    });

the error message is printed but it will not leave the zone :/

Any suggestions @pauldemarco ?

[sierraRhoades]

I was having the same problem. I found that doing my device connection call this way will properly handle the timeout occurrence. Its a little frustrating that if you declare the timeout in the parameters that you can't then declare an error handler. Maybe this could be updated where it gives you an on error option if you declare the timeout when first calling device.connect() ? @pauldemarco

   Future<bool> _connectToDevice() async
  {
    Future<bool> returnValue;
    await device.connect(timeout: Duration(seconds: 10)).timeout(Duration(seconds:10), onTimeout: (){
      debugPrint('timeout occured');
      returnValue = Future.value(false);
    }).then((data) {
      if(returnValue == null)
        {
          debugPrint('connection successful');
          returnValue = Future.value(true);
        }
    });

    return returnValue;
  }

if you remove the timeout within the .connect parameters there won't be an unhandeled exception error, however, I found that unless I put the timeout value within the connection parameters, it would still attempt to connect in the background even after the thrown timeout occurred.

I'm working with flutter_blue 0.6.0+1

[FWeissenb]

You can try this @sierraRhoades

 Future<bool> _connectToDevice(BluetoothDevice device,int timeout) async
  {
    Future<bool> returnValue;
    await device.connect(autoConnect: false).timeout(Duration(seconds:timeout), onTimeout: (){
      debugPrint('timeout occured');
      returnValue = Future.value(false);
      device.disconnect();
    }).then((data) {
      if(returnValue == null)
        {
          debugPrint('connection successful');
          returnValue = Future.value(true);
        }
    });

    return returnValue;
  }

So it will not reconnect and timeout is not handled in flutter_blue.

@pauldemarco is ther an other way ?

[sierraRhoades]

@FWeissenb
That worked thank you very much!

[FWeissenb]

@pauldemarco Can you please merge the PR to fix this?