Is there a way to access data coming from BLE device from single file which keeps updating? - flutter

Question

I want to access characteristic values of BLE from one dart file, What I am doing is that I am connecting the device from one activity and then sending the device info to all other activities. But to get values I have to write the same code again and again to all activities/dart files.
For example i am connecting device in an activity like this:
StreamBuilder<List<ScanResult>>(
stream: FlutterBlue.instance.scanResults,
initialData: [],
builder: (c, snapshot) => Column(
children: snapshot.data
.map(
(r) => ScanResultTile(
result: r,
onTap: () => Navigator.of(context)
.push(MaterialPageRoute(builder: (context) {
r.device.connect();
print('DEVICE CONNECTED');
return BluetoothConnectedSuccess(device: r.device);
Here device: r.device is the device that i have connected to my Flutter App. Now if i want to display device data i have to initilaze these lines of code everytime i jump to any screen/activity:
class BluetoothConnectedSuccess extends StatefulWidget {
const BluetoothConnectedSuccess({Key key, this.device}) : super(key: key);
final BluetoothDevice device;
#override
_BluetoothConnectedSuccessState createState() =>
_BluetoothConnectedSuccessState();
}
class _BluetoothConnectedSuccessState extends State<BluetoothConnectedSuccess> {
// BLE
final String SERVICE_UUID = "4fafc201-1fb5-459e-8fcc-c5c9c331914b";
final String CHARACTERISTIC_UUID = "beb5483e-36e1-4688-b7f5-ea07361b26a8";
bool isReady;
Stream<List<int>> stream;
List<int> lastValue;
List<double> traceDust = List();
#override
void initState() {
super.initState();
isReady = false;
connectToDevice();
}
connectToDevice() async {
await widget.device.connect();
discoverServices();
}
discoverServices() async {
List<BluetoothService> services = await widget.device.discoverServices();
services.forEach((service) {
if (service.uuid.toString() == SERVICE_UUID) {
service.characteristics.forEach((characteristic) {
if (characteristic.uuid.toString() == CHARACTERISTIC_UUID) {
characteristic.setNotifyValue(!characteristic.isNotifying);
stream = characteristic.value;
print(stream);
lastValue = characteristic.lastValue;
print(lastValue);
setState(() {
isReady = true;
});
}
});
}
});
}
_dataParser(List<int> data) {
var value = Uint8List.fromList(data);
print("stream.value: $value"); // stream.value: [33]
var hr = ByteData.sublistView(value, 0, 1);
print("Heart rate: ${hr.getUint8(0)}");
return hr.getUint8(0); // Heart rate: 33
}
It's creating a lot of mess to write the same code again and again to the activities where BLE data is needed.
Is there a way to only call this connected device from a single file instead of initializing the same code in every activity?
This is the link to my repo for a look at what I am doing on every activity/screen with BLE device data.
Please help me out as I am new to Flutter. Thank you

Answer 1

Firstly learn basic of state management using Get you can refer to my code here what happens is every time something changes or upadtes it will immediate show in UI using specific Get Widgets like Obx and GetX , these widgets listen to changes in value which are marked with obs (observable).
for exmaple :
Obx(
() => ble.isScan.value ? LinearProgressIndicator() : SizedBox(),
),
this will observe the changes in isScan value .
class BleServices extends GetxController {
FlutterBlue blue = FlutterBlue.instance;
BluetoothDevice d;
var connectedDevices = List<BluetoothDevice>().obs;
var scanResults = List<ScanResult>().obs;
var bleState = BluetoothState.off.obs;
var isScan = false.obs;
var scanRequire = false.obs;
var bluetoothServices = List<BluetoothService>().obs;
var discoveringServices = false.obs;
var characteristics = List<BluetoothCharacteristic>().obs;
#override
void onInit() async {
super.onInit();
final perb = await Permission.bluetooth.status.isGranted;
final perL = await Permission.location.status.isGranted;
if (perb && perL) {
getConnectedDevices();
} else {
await Permission.bluetooth.request();
await Permission.location.request();
}
isScanning();
state();
}
isDiscovering() async {}
getConnectedDevices() async {
final connectedDevice = await blue.connectedDevices;
connectedDevices.value = connectedDevice;
AppLogger.print('connected devices : $connectedDevice');
if (connectedDevice.length == 0) {
scanRequire.value = true;
searchDevices();
}
return connectedDevice;
}
searchDevices() {
// AppLogger.print('pppppppppppppp');
blue
.scan(timeout: Duration(seconds: 20))
.distinct()
.asBroadcastStream()
.listen((event) {
AppLogger.print(event.toString());
scanResults.addIf(!scanResults.contains(event), event);
});
Future.delayed(Duration(seconds: 20), () {
blue.stopScan();
Get.showSnackbar(GetBar(
message: 'scan is finished',
));
});
}
isScanning() {
blue.isScanning.listen((event) {
AppLogger.print(event.toString());
isScan.value = event;
});
}
state() {
blue.state.listen((event) {
AppLogger.print(event.toString());
bleState.value = event;
});
}
}