Android can't find any BLE devices

Question

Here's he problem. I've developed an app for iOS to control an BLE LED device (and a few other things). Everything works fine and smooth. Now I wanted develop the same app for android and I already fail at the scanning of BLE devices. I have tried a few tutorials and sample codes but whatever I do I can't find any devices. I work on a Moto G4 Play. The bluetooth works and I can pair devices in the settings but it won't work with any sample code/tutorial I've tried. For example this one: https://github.com/kaviles/BLE_Tutorials

I build this app as it is and it can't find anything.

So I downloaded a BLE Scanner from the Playstore and that works fine to and finds all devices.

I know it's hard to say without any sample code but I've tried so many and I'm not sure if I miss something completely basic.

Answer 1

As discussed in the comments, you have to set up the permissions accordingly if your targetSdk is 23+ or other. The location services must be on.

Manifest permissions for API 23+:

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission-sdk-23 android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission-sdk-23 android:name="android.permission.ACCESS_COARSE_LOCATION"/>

To check bluetooth permissions:

    public boolean hasBlePermissions() {
        if (ContextCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED ||
                ContextCompat.checkSelfPermission(mContext, Manifest.permission.ACCESS_COARSE_LOCATION)
                        != PackageManager.PERMISSION_GRANTED) {
            return false;
        } else {
            return true;
        }
    }

To request runtime permissions with :

public void requestBlePermissions(final Activity activity, int requestCode) {
    ActivityCompat.requestPermissions(activity,
            new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION},
            requestCode);
}

Then to check the grant results from OnRequestPermissionResult:

public boolean checkGrantResults(String[] permissions, int[] grantResults) {
    int granted = 0;

    if (grantResults.length > 0) {
        for(int i = 0; i < permissions.length ; i++) {
            String permission = permissions[i];
            if (permission.equals(Manifest.permission.ACCESS_FINE_LOCATION) ||
                    permission.equals(Manifest.permission.ACCESS_COARSE_LOCATION)) {
                if (grantResults[i] == PackageManager.PERMISSION_GRANTED) {
                    granted++;
                }
            }
        }
    } else { // if cancelled
        return false;
    }

    return granted == 2;
}

Check location services:

public boolean areLocationServicesEnabled(Context context) {
    LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
    try {
        return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) ||
                locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
    } catch (Exception e) {
        e.printStackTrace();
        return false;
    }
}