This lib allows you to track your coordinate calculated from distances to Bluetooth Low Energy (BLE) devices around. This lib only produces approximate coordinates, since RSSI of same beacon goes up and down all the time on same distance. Also you should note that if there's an obstacle between current device and beacon, rssi signal will go down which will increase the distance to the beacon and this can be a cause to wrong coordinates in result.

To track coordinates you want to place at least 3 beacon around (not in single line). It's better to place beacon on the perimeter. You also want to configure beacon's txPower constant for each device before using it. This is not necessary but will drastically increase the accuracy. The configuration can be done via BeaconSet+. The configuration scenary is the following:

• You need to measure beacon's rssi at 1m
• This rssi should be sumed with 41 where 41 is typical signal loss at 1 meter.
• THe resulting value should be set as TxPower.

For example if rssi at 1 meter is -56db, txPower should be set to -15.

Check MainActivity.kt and MainActivityJava.java as examples.

The lib contains of 2 main classes BeaconsSearcher and CoordinateCalculator. BeaconsSearcher notifies whenever it finds a new ble device. CoordinateCalculator is registered to beaconSearcher as accepts BLE device and if it matches the registered one - calculates the current coordinates based on distance to it.

So for the minimal use you want to register beacons with [x,y] position using .addBeacon(new Beacon("00112233445566778899", "000000000000"), new XYPoint(0.0, 0.0)) where 00112233445566778899 is namespace of the beacon and 000000000000 is instance. 0.0 and 0.0 is [x,y] position on the map for the beacon.

    CoordinateCalculator cc = new CoordinateBuilder()
        .addBeacon(new Beacon("00112233445566778899", "000000000000"), new XYPoint(0.0, 0.0))
        .addBeacon(new Beacon("00112233445566778899", "111111111111"), new XYPoint(3.07, 0.0))
        .addBeacon(new Beacon("00112233445566778899", "000000111111"), new XYPoint(3.07, 5.66))
        .trackCoordinate(new CoordinateTracker() {
          @Override
          public void onCoordinateChange(double x, double y) {
            Log.d("BLE", String.format("{%.2f, %.2f}", x, y));
          }
        })
        .build();
    BeaconsSearcher bs = new BeaconsSearcher(new OnScanError() {
      @Override
      public void onError(@NotNull ErrorType description) {
        Toast.makeText(MainActivityJava.this, description.getDescription(), Toast.LENGTH_LONG).show();
      }
    }, cc);

    bs.scanForDevices(YourActivity.this);

Permissions are already specified in library's AndroidManifest. This manifest will be merged with yours when apk is assembled. However for android6.0+ you also should ask for bluetooth permissions at runtime:

if (!isBluetoothGranted()) {
  askBTPermissions()
} else {
 bs.scanForDevices(this);
}
   

Permissions methods:

 private Boolean isPermissionGranted(Context c, String... permissions) {
    Boolean granted = true;
    for (String permission : permissions) {
      granted = granted & (PackageManager.PERMISSION_GRANTED
          == ContextCompat.checkSelfPermission(c, permission));
    }
    return granted;
  }

  private Boolean isBluetoothGranted() {
    return isPermissionGranted(this,
        Manifest.permission.ACCESS_COARSE_LOCATION,
        Manifest.permission.ACCESS_FINE_LOCATION,
        Manifest.permission.BLUETOOTH_ADMIN,
        Manifest.permission.BLUETOOTH
    );
  }

  private void askBTPermissions() {
    ActivityCompat.requestPermissions(
        this,
        new String[]{Manifest.permission.ACCESS_FINE_LOCATION,
            Manifest.permission.ACCESS_COARSE_LOCATION,
            Manifest.permission.BLUETOOTH_ADMIN,
            Manifest.permission.BLUETOOTH
        },
        444);
  }

You can enable library logs with builder.enableLogs()

builder
 .trackDistance(new DistanceTracker() {
    @Override
    public void onDistanceChange(@NotNull Beacon i, double current, double medium) {
      Log.d("BLE", String.format("Current distance to  %s  is %.2f (average is %.2f)", i, current, medium));
    }
})

By default library saves beacon rssi and then calculates the distance based on average rssi to each beacon. By default this time is 4 seconds. You can turn this feature off with builder.cacheTime(null) or configure this time with same method.

By default library uses Math.pow(10.0, (txPower - SIGNAL_LOSS_1M - rssi) / (10 * 2)) which seems to give more accurate result than others. If you want to use common formula which is (coef1)*((rssi/power)^coef2) + coef3, you can set coefficients with

builder.withCalcMethod(coef1, coef2, coef3)