LE ScanRecord 的 getServiceData() 返回 null

Question

I'm trying to implement Bluetooth advertiser and scanner. My advertiser code is advertising with some service data in the advertisement packet. On the scanner side when I tried to get the data using the same UUID that is used during adding service data in the advertiser the getService data method is returning null object. Here is my advertiser code.

public class Main_Service extends Service{
private BluetoothAdapter mBluetoothAdapter;
private BluetoothLeAdvertiser mBluetoothLeAdvertiser;
private Intent mIntent;
private String RSSI,SSID,MAC;
@Override
public IBinder onBind(Intent intent) {
    return null;
}
public int onStartCommand (Intent intent, int flags, int startId) {
    RSSI = intent.getStringExtra("RSSI");
    SSID = intent.getStringExtra("SSID");
    MAC= intent.getStringExtra("MAC");
    Toast.makeText(this, RSSI+";"+SSID+";"+MAC+":", Toast.LENGTH_LONG).show();
    initialize();
    startadvertising();
    return 0;
}
public void onCreate() {
    Toast.makeText(this, "Service Created", Toast.LENGTH_LONG).show();
}
private void startadvertising() {
    AdvertiseSettings settings = buildAdvertiseSettings();
    AdvertiseData data = buildAdvertiseData();
    if (mBluetoothLeAdvertiser != null) {
        mBluetoothLeAdvertiser.startAdvertising(settings, data, new AdvertiseCallback() {
            @Override
            public void onStartSuccess(AdvertiseSettings settingsInEffect) {
                super.onStartSuccess(settingsInEffect);
                Toast.makeText(getBaseContext(), "Adertising", Toast.LENGTH_LONG).show();
            }

            @Override
            public void onStartFailure(int errorCode) {
                super.onStartFailure(errorCode);
                Toast.makeText(getBaseContext(), "Advertisement failed", Toast.LENGTH_LONG).show();
            }
        });
    }
    else{
        Toast.makeText(getBaseContext(), "BLE is not supported", Toast.LENGTH_LONG).show();
    }
}
private void initialize() {
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if(mBluetoothAdapter!=null){
        if(!mBluetoothAdapter.isEnabled()){
            mBluetoothAdapter.enable();
        }
    }
    else{
        Toast.makeText(getBaseContext(), "BL is not supported", Toast.LENGTH_LONG).show();
    }
    mBluetoothLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();
}
private AdvertiseSettings buildAdvertiseSettings() {
    AdvertiseSettings.Builder settingsBuilder = new AdvertiseSettings.Builder();
    settingsBuilder.setAdvertiseMode(AdvertiseSettings.ADVERTISE_MODE_LOW_POWER);
    settingsBuilder.setTimeout(0);
    return settingsBuilder.build();
}
private AdvertiseData buildAdvertiseData() {
    AdvertiseData.Builder dataBuilder = new AdvertiseData.Builder();
    //String data = RSSI+SSID.substring(0,10)+MAC.replaceAll(":","");
    byte[] serviceData = new byte[15];
    serviceData[0] = (byte)Integer.parseInt(RSSI);
    String[] macAddressParts = MAC.split(":");
    for(int i=0; i<6; i++){
        Integer hex = Integer.parseInt(macAddressParts[i], 16);
        serviceData[i+1] = hex.byteValue();
    }
    for(int i=0;i<8;i++) {
        serviceData[i+7] = (byte)(SSID.charAt(i));
    }
    long mostsignificant=0,leastsignificant=5122;
    UUID s_id = new UUID(mostsignificant,leastsignificant);
    dataBuilder.addServiceData(new ParcelUuid(s_id),serviceData);
    Toast.makeText(this, s_id.toString(), Toast.LENGTH_LONG).show();
    return dataBuilder.build();
}
public void onStart(Intent intent, int startid) {
    Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
}
public void onDestroy() {
    mBluetoothAdapter = null;
    mBluetoothLeAdvertiser = null;
    Toast.makeText(this, "Service Stopped", Toast.LENGTH_LONG).show();
}
}

Answer 1

In normal BLE flow, We need to call discoverService() after establishing a successful connection with the BLE device. We will get a callback in onServiceDiscoverd(). After that, we need to approach the getService() with corresponding Service & Characteristic UUID. Before discoverService() call, the getService() will always return null. I hope this will help you. If you required, I can share my complete service flow.