How to use flutter_blue with flutter_isolate?

[vikramkapoor]

Thank you for writing this plugin. I am trying to use flutter_blue with this to listen to bluetooth notifications in background. However, I always get state = BluetoothState.unknown from the background isolate when I check flutterBlue.state. The same call gets state = BluetoothState.on from the foreground. Am I using this correctly?

void isolate1(SendPort sendPort) async {

FlutterBlue flutterBlue = FlutterBlue.instance;

/// State
StreamSubscription _stateSubscription;
BluetoothState state = BluetoothState.unknown;

/// Scanning
StreamSubscription _scanSubscription;
Map<DeviceIdentifier, ScanResult> scanResults = new Map();
bool isScanning = true;

/// Device
BluetoothDevice device;
//bool get isConnected => (device != null);
StreamSubscription deviceConnection;
StreamSubscription deviceStateSubscription;
List services = new List();
Map<Guid, StreamSubscription> valueChangedSubscriptions = {};
BluetoothDeviceState deviceState = BluetoothDeviceState.disconnected;

flutterBlue.setUniqueId('FlutterBlue');

// Immediately get the state of FlutterBlue

print ("Get bluetooth state");
flutterBlue.state.then((s) {
state = s;
if (state != BluetoothState.on) {
print("Please turn bluetooth on");
}
else {
print("Bluetooth is on. Starting scan");
_scanSubscription = flutterBlue.scan(
timeout: const Duration(seconds: 30),
withServices: [
new Guid('0000FFE0-0000-1000-8000-00805F9B34FB')
]).listen((scanResult) {
print('localName: ${scanResult.advertisementData.localName}');
print(
'manufacturerData: ${scanResult.advertisementData.manufacturerData}');
print('serviceData: ${scanResult.advertisementData.serviceData}');
scanResults[scanResult.device.id] = scanResult;
//_stopScan();
//_connect(scanResult.device);
},
);
}
});
/*
ReceivePort conPort;
sendPort.send(conPort );
print('Spawning isolate 2');
final isolate = await FlutterIsolate.spawn(isolate2, "hello2");
FlutterStartup.startupReason.then((reason) {
print("Isolate1 $reason");
});*/
int counter = 0;
Timer.periodic(new Duration(seconds: 1), (Timer t) {
counter++;
String msg = 'notification ' + counter.toString();
print('SEND: ' + msg + ' - ');
sendPort.send(msg);
});
Timer.periodic(
Duration(seconds: 1), (timer) => print("Timer Running From Isolate 1"));
}

[vikramkapoor]

I fixed this issue by creating a custom registrant. Generated registrant has a lot of plugins which were trying to register an Activity from background isolate which led to an error that prevented Flutter_blue registration.

[MichealReed]

@vikramkapoor mind sharing your updated code?

[vikramkapoor]

Hi MichaelReed, Sorry I just saw this. Do you still need this?

Here's the code for custom registrant

Custom Registrant

package io.flutter.plugins;

import io.flutter.plugin.common.PluginRegistry;
import com.pauldemarco.flutterblue.FlutterBluePlugin;


/**
 * Generated file. Do not edit.
 */
public final class IsolatePluginRegistrant {
  public static void registerWith(PluginRegistry registry) {
    if (alreadyRegisteredWith(registry)) {
      return;
    }
    FlutterBluePlugin.registerWith(registry.registrarFor("com.pauldemarco.flutterblue.FlutterBluePlugin"));

  }

  private static boolean alreadyRegisteredWith(PluginRegistry registry) {
    final String key = IsolatePluginRegistrant.class.getCanonicalName();
    if (registry.hasPlugin(key)) {
      return true;
    }
    registry.registrarFor(key);
    return false;
  }
}

Invoke custom registrant from MainActivity

package com.rakshak.safeho

import android.content.Intent
import android.os.Bundle
import io.flutter.app.FlutterActivity
import io.flutter.plugins.GeneratedPluginRegistrant
import io.flutter.plugins.IsolatePluginRegistrant
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
import com.rmawatson.flutterisolate.FlutterIsolatePlugin
import com.google.android.gms.actions.NoteIntents

class MainActivity(): FlutterActivity() {
     var savedNote:String? = null

    override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    FlutterIsolatePlugin.setCustomIsolateRegistrant(IsolatePluginRegistrant::class.java)
    GeneratedPluginRegistrant.registerWith(this)
    var intent = getIntent()
    var action = intent.getAction()
    var type = intent.getType()

    if (NoteIntents.ACTION_CREATE_NOTE.equals(action) && type != null) {
      if ("text/plain".equals(type)) {
        savedNote = intent.getStringExtra(Intent.EXTRA_TEXT)
      }
  }
      MethodChannel(getFlutterView(), "app.channel.shared.data").setMethodCallHandler { call, result ->
          if (call.method == "getSavedNote") {
              result.success(savedNote)
              savedNote = null
          }
      }
  }
}