onEndpointFound never gets called in dart code. Error : FlutterJNI(26633): Tried to send a platform message to Flutter, but FlutterJNI was detached from native C++. Could not send. Channel: nearby_connections. Response ID: 4

[rahulmaindargi]

Below is the error when discovery finds a device. but onEndpointFound on dart side never gets called.

NearbyConnections(26633): NFC discovery started. D/NearbyConnections(26633): Invalidating dispatch state. D/NearbyConnections(26633): Starting NFC dispatching. D/NearbyConnections(26633): Cannot dispatch NFC events. NFC is not supported. D/nearby_connections(26633): startDiscovery D/nearby_connections(26633): onEndpointFound W/FlutterJNI(26633): Tried to send a platform message to Flutter, but FlutterJNI was detached from native C++. Could not send. Channel: nearby_connections. Response ID: 4

[mannprerak2]

Are you using this in a background service?

This package is not built in a way to be used inside a background service, and I'm not sure if it's even possible to do so.

[rahulmaindargi]

No I am not using as background service. but its using a separate isolate after connection is initialized.

I am working on a expense manager app , and want to sync/send data over nearby communication. I am using bloc cubit. I use separate isolate so that I can show progress of transfer over UI

To be exact, on bloc cubit call, I start nearby Discover, on endpoint found, I request connection, once connection is approved onConnectionInitiated I stop discovery, then then try to send data separate isolate.

but code never reaches upto isolate part. on on endpoint found callback never gets called and in console I get above error message.

[rahulmaindargi]

I have no experience of plugin/package development, but from stackoverflow

As per first answer, root cause appears to be using the wrong (or old) method channel. inside plugin/package code. so raised the issue here.

[rahulmaindargi]

if it helps here is my cubit.sendDatamethod has below code

await Nearby().startDiscovery(
        configId,
        Strategy.P2P_POINT_TO_POINT, // https://developers.google.com/nearby/connections/strategies
        onEndpointFound: (String id, String userName, String serviceId) {
          // called when an advertiser is
          logger.d("onEndpointFound $id $userName $serviceId");
}
...

but execution never reaches logger line mentioned, it fails and gives above error.

[mannprerak2]

I'm guessing you cannot use a separate isolate, all the nearby connection interaction including any callbacks must be done in the main isolate itself.

Try removing the isolate usage.

[rahulmaindargi]

but code doesn't even reach the isolate part. any isolate related code will come into execution only after onConnectionInitiated but ENdpoint found fails itself.

I will try commenting the actual business logic (that involves isolate) tomorrow and update here. but I am 99% sure, its not the cause for the issue.

Kindly check below stackoverflow thread once you get time.

https://stackoverflow.com/questions/61934900/tried-to-send-a-platform-message-to-flutter-but-flutterjni-was-detached-from-n

[mannprerak2]

Method channel is not being cached. See https://github.com/mannprerak2/nearby_connections/blob/63104a9afc7a07699e67f2b91ab372e8556dd59c/android/src/main/java/com/pkmnapps/nearby_connections/NearbyConnectionsPlugin.java#L449

I'm guessing you are somehow using an isolate to call the nearby connection function. To be sure you can try running the example app on your device, if that works it's probably because of isolate usage.

If you are still not sure, you can post a link to a minimal reproducible sample I might be able to check it out over the weekend.

[rahulmaindargi]

Sorry for so late reply.

I found that

bool a = await Nearby().startAdvertising(...); logger.d("Advertising started $a"); never completes the future i.e. logger line never gets executed neither any error.

[rahulmaindargi]

bool a = await Nearby().startAdvertising(...); logger.d("Advertising started $a"); never completes the future i.e. logger line never gets executed neither any error.

Sorry looks like flutter version upgrade messed with gradle big time. will check and let you know