Develop Reference

Android fetchUuidsWithSdp() giving UUIDs in little endian representation

I am building a bluetooth service discovery on Android using BluetoohDevice.fetchUuidsWithSdp().
Currently i test the code on 3 different devices:
devices "A" and "B" running Android 8.1.0
device "C" is on 5.1.1.
Each device can act as Bluetooth server
using
mBluetoothAdapter.listenUsingInsecureRfcommWithServiceRecord(serviceName, serviceUUID)
or as Bluetooth client
mmDevice.createRfcommSocketToServiceRecord(serviceUUID);
If a server is discovered by a client device the UUIDs of services running on the server will be fetched using fetchUuidsWithSdp().
Then i get the UUIDs in the BroadcastReceiver:
private BroadcastReceiver UUIDFetchedReceiver = new BroadcastReceiver()
{
#Override
public void onReceive(Context context, Intent intent)
{
final String action = intent.getAction();
if (action.equals(BluetoothDevice.ACTION_UUID))
{
try
{
// Getting the Service UUIDs
Parcelable[] uuidExtra = intent.getParcelableArrayExtra(BluetoothDevice.EXTRA_UUID);
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
Log.d(TAG, "UUIDFetchedReceiver: received device: " + device.getName());
for (Parcelable uuid : uuidExtra)
{
Log.d(TAG, "UUIDFetchedReceiver: Service found on " + device.getName() + " | uuid: " + uuid);
if (uuid.toString().equals("3253f2d2-f49a-11ec-b939-0242ac120002"))
{
foundSDPService(device, uuid.toString());
}
}
}
catch (NullPointerException e)
{
Log.e(TAG, "UUIDFetchedReceiver: Nu UUIDs received ");
}
}
}
};
That works on device "A" and "C" the log output there shows:
UUIDFetchedReceiver: Service found on Device B | uuid: 3253f2d2-f49a-11ec-b939-0242ac120002
On Device "B" it looks like this:
UUIDFetchedReceiver: Service found on Device A | uuid: 020012ac-4202-39b9-ec11-9af4d2f25332
Device "B" shows the same UUID but as little endian.
The code is the same and for device "A" and "B" even the Android version is the same.
Does anybody know what causes this issue and how it can be fixed?
The devices are:
A = Samsung Galaxy Tab A (2016)
B = Lenovo TB-X304L
C = LG G Flex 2
The problem seems to be similar to the one described in this Question :
Strange UUID reversal from fetchUuidsWithSdp

Scan Ble Android / getName() or device not complete or null

I'have an issue with the BLE scan of Android, I dont get the full name of the scanned devices found, I get only the first letter do you have any idea how to resolve this issue ?
I'm working with a 7.0 Nougat device which is supporting BLE
This is a part of my code :
mBluetoothScanner = mBluetoothAdapter.getBluetoothLeScanner();
settings = new ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)
.build();
if (Build.VERSION.SDK_INT >= 21) {
mScanCallback = new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
messageLog.error("onScanResult");
BluetoothDevice btDevice = null;
if (Build.VERSION.SDK_INT >= 21) {
btDevice = result.getDevice();
messageLog.error("btDevice : " + btDevice.getName() + "|" + btDevice.getAddress() + "|" + Arrays.toString(btDevice.getUuids()));
}
if (btDevice != null && btDevice.getName() != null && !isInDeviceList(btDevice))
mDeviceList.add(btDevice);
}
#Override
public void onBatchScanResults(List<ScanResult> results) {
}
#Override
public void onScanFailed(int errorCode) {
Log.e("Scan Failed", "Error Code: " + errorCode);
}
};
}
With btDevice.getName( ) I only get the first letter of a device scanned, is this my fault or is it coming from the Android BLE API ?

If the peripheral's name does not fit in the Advertising data since it needs to include other data therein, it will only send the prefix of the name over the air. It's nothing you can do about that other than change the advertisement data in the peripheral's firmware.
To get the exact advertisement data, you can investigate the "result.getScanRecord()" ScanRecord in onScanResult.

Connect to Bluetooth programmatically

I'm trying to connect programmatically my device to for example on my Headsets... I had KitKat version and all worked perfect (Bluetooth always was connecting without problems autommatically) but since I've updated to Lolipop it doesn't. I'd like to know if there is any way to connect any paired device of my Android phone to Bluetooth when it turns on.
Since now I've this code (gets the Device name and Device Address) because I thought with it I could connect doing something like device.connect(MAC-Address); but it didn't work...
BluetoothAdapter bluetoothAdapter
= BluetoothAdapter.getDefaultAdapter();
Set < BluetoothDevice > pairedDevices = bluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
for (BluetoothDevice device: pairedDevices) {
mDeviceName.add(device.getName());
mDeviceMAC.add(device.getAddress());
}
}
bluetoothClass.setDeviceName(mDeviceName);
bluetoothClass.setDeviceMac(mDeviceMAC);
Question
On my MotoG (KitKat) if I turn my Bluetooth it connects autommatically to device (if it's near and paired ofc...) but on my LG G3 I must go to Configuration/Bluetooth/Paired devices/ and there tap the device to connect... and I want to avoid this... should be possible?
I would like to know if there is any possibility to connect to specific Bluetooth just adding the Device name or Device MAC... More or less like Android does when I click on my device to connect it connects autommatically... I just want to get that CLICK event.
I know that Android should connect autommatically to a paired device but there's any exceptions that doesn not ... the only way to pair it it's doing the click... that's why I'm wondering if it's there a way to do it...
I've read and tested kcoppock answer but it still don't work ..
Any suggestion?
EDIT
The main thing that I wanted to do is to connect my Bluetooth autommatically but since I've read on Hey you answer... I figured it out and I know it's an Android bug, so the thing that I would like to do is select the paired devices and then click on the device that I want to connect (Without doing any Intent) and connect it, instead to go Configuration/Bluetooth/....
Btw I've read any answers on StackOverflow and I found something with Sockets are they used to connect Bluetooth?Could be it a solution?

Edit to answer latest question
You can avoid using an intent to search for paired devices. When connecting to a device that is not paired, a notification will pop up asking to pair the devices. Once paired this message should not show again for these devices, the connection should be automatic (according to how you have written your program).
I use an intent to enable bluetooth, and to make my device discoverable, I then set up my code to connect, and press a button to connect. In your case, you will need to ensure your accessories are discoverable also. In my case I use a unique UUID, and both devices must recognise this to connect. This can only be used if you are programming both devices, whether both are android or one android and one other device type.
Try this, and see if it solves your problem.
This answer is to the original question before it was edited to be another question.
I've edited my answer for clarity as I can see from the comments it is misleading. Your question has two parts.
On my MotoG (KitKat) if I turn my Bluetooth it connects autommatically
to device (if it's near and paired ofc...) but on my LG G3 I must go
to Configuration/Bluetooth/Paired devices/ and there tap the device to
connect... and I want to avoid this... should be possible?
This is less of a programming issue and more of a platform issue.
There is a well documented bug in Android 5.0 with Bluetooth not automatically connecting and many other BT issues. These issues continue with all the updates on 5.0. versions and is not fixed until the 5.1. upgrade.
http://www.digitaltrends.com/mobile/android-lollipop-problems/11/
http://forums.androidcentral.com/lg-g3/473064-bluetooth-streaming-choppy-lg-3-lollipop.html
First port of call is to update to 5.1
These issues have been addressed in the Lollipop update 5.1
http://www.reddit.com/r/Android/comments/306m3y/lollipop_51_bluetooth/
Edit:
I don't believe this is going to fix your problem of the automatic pairing, you wanted to know how to use BTGatt.
I've seen if I type device. to check what can I do it let me
connectGatt() means /.../
But I can't figure it out how to do this...
To use BluetoothGatt
https://developer.android.com/reference/android/bluetooth/BluetoothGatt.html
This class provides Bluetooth GATT functionality to enable
communication with Bluetooth Smart or Smart Ready devices.
/.../
GATT capable devices can be discovered using the Bluetooth device
discovery or BLE scan process.
https://developer.android.com/reference/android/bluetooth/BluetoothGattCallback.html
Here is a great example of how to use BluetoothGatt (it uses hear rate):
https://github.com/googlesamples/android-BluetoothLeGatt/blob/master/Application/src/main/java/com/example/android/bluetoothlegatt/BluetoothLeService.java
I have reproduced some of the code here, in case the link dies.
It basically follows similar lines to a regular bluetooth connection. You need to discover and find supported devices.
Monitor state, etc.
These are the two most pertinent features to gatt.
The callback:
// Implements callback methods for GATT events that the app cares about. For example,
// connection change and services discovered.
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
broadcastUpdate(intentAction);
Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
Log.i(TAG, "Disconnected from GATT server.");
broadcastUpdate(intentAction);
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
} else {
Log.w(TAG, "onServicesDiscovered received: " + status);
}
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic,
int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
}
};
The broadcast:
private void broadcastUpdate(final String action,
final BluetoothGattCharacteristic characteristic) {
final Intent intent = new Intent(action);
// This is special handling for the Heart Rate Measurement profile. Data parsing is
// carried out as per profile specifications:
// http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
int flag = characteristic.getProperties();
int format = -1;
if ((flag & 0x01) != 0) {
format = BluetoothGattCharacteristic.FORMAT_UINT16;
Log.d(TAG, "Heart rate format UINT16.");
} else {
format = BluetoothGattCharacteristic.FORMAT_UINT8;
Log.d(TAG, "Heart rate format UINT8.");
}
final int heartRate = characteristic.getIntValue(format, 1);
Log.d(TAG, String.format("Received heart rate: %d", heartRate));
intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
} else {
// For all other profiles, writes the data formatted in HEX.
final byte[] data = characteristic.getValue();
if (data != null && data.length > 0) {
final StringBuilder stringBuilder = new StringBuilder(data.length);
for(byte byteChar : data)
stringBuilder.append(String.format("%02X ", byteChar));
intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
}
}
sendBroadcast(intent);
}
This question also has some relevant code that may help cut it down when learning:
BLuetooth Gatt Callback not working with new API for Lollipop
Now here's the rub. Are your devices bluetooth smart or smart ready?
This link gives a great list of smart devices. You will also find out when you implement your program.
http://www.bluetooth.com/Pages/Bluetooth-Smart-Devices-List.aspx

This is how i made this work using Java Reflection and BluetoothProfile:
Attributes:
private boolean mIsConnect = true;
private BluetoothDevice mDevice;
private BluetoothA2dp mBluetoothA2DP;
private BluetoothHeadset mBluetoothHeadset;
private BluetoothHealth mBluetoothHealth;
Call:
mBluetoothAdapter.getProfileProxy(getApplicationContext() , mProfileListener, BluetoothProfile.A2DP);
mBluetoothAdapter.getProfileProxy(getApplicationContext() , mProfileListener, BluetoothProfile.HEADSET);
mBluetoothAdapter.getProfileProxy(getApplicationContext() , mProfileListener, BluetoothProfile.HEALTH);
Listener:
private BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() {
public void onServiceConnected(int profile, BluetoothProfile proxy) {
if (profile == BluetoothProfile.A2DP) {
mBluetoothA2DP = (BluetoothA2dp) proxy;
try {
if (mIsConnect) {
Method connect = BluetoothA2dp.class.getDeclaredMethod("connect", BluetoothDevice.class);
connect.setAccessible(true);
connect.invoke(mBluetoothA2DP, mDevice);
} else {
Method disconnect = BluetoothA2dp.class.getDeclaredMethod("disconnect", BluetoothDevice.class);
disconnect.setAccessible(true);
disconnect.invoke(mBluetoothA2DP, mDevice);
}
}catch (Exception e){
} finally {
}
} else if (profile == BluetoothProfile.HEADSET) {
mBluetoothHeadset = (BluetoothHeadset) proxy;
try {
if (mIsConnect) {
Method connect = BluetoothHeadset.class.getDeclaredMethod("connect", BluetoothDevice.class);
connect.setAccessible(true);
connect.invoke(mBluetoothHeadset, mDevice);
} else {
Method disconnect = BluetoothHeadset.class.getDeclaredMethod("disconnect", BluetoothDevice.class);
disconnect.setAccessible(true);
disconnect.invoke(mBluetoothHeadset, mDevice);
}
}catch (Exception e){
} finally {
}
} else if (profile == BluetoothProfile.HEALTH) {
mBluetoothHealth = (BluetoothHealth) proxy;
try {
if (mIsConnect) {
Method connect = BluetoothHealth.class.getDeclaredMethod("connect", BluetoothDevice.class);
connect.setAccessible(true);
connect.invoke(mBluetoothHealth, mDevice);
} else {
Method disconnect = BluetoothHealth.class.getDeclaredMethod("disconnect", BluetoothDevice.class);
disconnect.setAccessible(true);
disconnect.invoke(mBluetoothHealth, mDevice);
}
}catch (Exception e){
} finally {
}
}
}
public void onServiceDisconnected(int profile) {
}
};
I hope this helps anyone trying to connect to Bluetooth Audio devices and headsets.

android device.getUuids returns null

I'm trying to connect to an Arduino Uno via an android app using Bluetooth Low Energy (BLE).
I'm developing on Android Studio, testing with a Samsung Galaxy S4, and with an Android version 5.0.1
I followed this link: http://www.truiton.com/2015/04/android-bluetooth-low-energy-ble-example/
I'm scanning devices and when I found one, I would like to get it's UUID before connecting to it, to make sure that it's the right type of device:
mScanCallback = new ScanCallback() {
#Override
#TargetApi(21)
public void onScanResult(int callbackType, ScanResult result) {
BluetoothDevice btDevice = result.getDevice();
ParcelUuid[] uuids = btDevice.getUuids(); //<-- this is always null!! :(
Log.d(TAG, ""+btDevice.fetchUuidsWithSdp()); //<-- prints true.
Log.d(TAG, "result : " + result.toString()); //<-- prints a bunch of relevant info that contains the UUID I want to check.
Log.d(TAG, "uuids : " + uuids); //<-- prints null.
/*
for (ParcelUuid u : uuids) {
//Compare with the UUID of my device, and connect if ok.
}
*/
}
However, btDevice.getUuids(); is always returning null with no error...
How can I get the UUID of the scanned device?
A brute force method would be to use regexp with the result.toString() to grab what I want but there must be a better way isn't it?
Thanks

BluetoothLeScanner scanner = mBluetoothAdapter.getBluetoothLeScanner();
// scan for devices
scanner.startScan(new ScanCallback() {
#TargetApi(Build.VERSION_CODES.LOLLIPOP)
#Override
public void onScanResult(int callbackType, ScanResult result)
{
List<ParcelUuid> uuids = result.getScanRecord().getServiceUuids();
}
}
this is worked for me in Android 6.0.1

After hours of searching I find out that getUuid() is not the way to go if you want to retrieve the uuid of an iBeacon.
If that is the case, you need to get it directly from the Scan result result object.
I managed to work by using the answer provided by ADEBAYO OSIPITAN.
BLE obtain uuid encoded in advertising packet
Here is his code snipet:
//For APIs greater than 21, Returns Device UUID
public String getUUID(ScanResult result){
String UUIDx = UUID
.nameUUIDFromBytes(result.getScanRecord().getBytes()).toString();
return UUIDx;
}

From Java DOC:
public ParcelUuid[] getUuids ()
Added in API level 15
Returns the supported features (UUIDs) of the remote device.
This method does not start a service discovery procedure to retrieve the UUIDs from the remote device. Instead, the local cached copy of the service UUIDs are returned.
Use fetchUuidsWithSdp() if fresh UUIDs are desired.
Requires BLUETOOTH.
Returns
the supported features (UUIDs) of the remote device, or null on error
Your ScanResult probably is a error

list connected bluetooth devices?

How can I list all connected bluetooth devices on android ?
thanks!

public void checkConnected()
{
// true == headset connected && connected headset is support hands free
int state = BluetoothAdapter.getDefaultAdapter().getProfileConnectionState(BluetoothProfile.HEADSET);
if (state != BluetoothProfile.STATE_CONNECTED)
return;
try
{
BluetoothAdapter.getDefaultAdapter().getProfileProxy(_context, serviceListener, BluetoothProfile.HEADSET);
}
catch (Exception e)
{
e.printStackTrace();
}
}
private ServiceListener serviceListener = new ServiceListener()
{
#Override
public void onServiceDisconnected(int profile)
{
}
#Override
public void onServiceConnected(int profile, BluetoothProfile proxy)
{
for (BluetoothDevice device : proxy.getConnectedDevices())
{
Log.i("onServiceConnected", "|" + device.getName() + " | " + device.getAddress() + " | " + proxy.getConnectionState(device) + "(connected = "
+ BluetoothProfile.STATE_CONNECTED + ")");
}
BluetoothAdapter.getDefaultAdapter().closeProfileProxy(profile, proxy);
}
};

As of API 14 (Ice Cream), Android has a some new BluetoothAdapter methods including:
public int getProfileConnectionState (int profile)
where profile is one of HEALTH, HEADSET, A2DP
Check response, if it's not STATE_DISCONNECTED you know you have a live connection.
Here is code example that will work on any API device:
BluetoothAdapter mAdapter;
/**
* Check if a headset type device is currently connected.
*
* Always returns false prior to API 14
*
* #return true if connected
*/
public boolean isVoiceConnected() {
boolean retval = false;
try {
Method method = mAdapter.getClass().getMethod("getProfileConnectionState", int.class);
// retval = mAdapter.getProfileConnectionState(android.bluetooth.BluetoothProfile.HEADSET) != android.bluetooth.BluetoothProfile.STATE_DISCONNECTED;
retval = (Integer)method.invoke(mAdapter, 1) != 0;
} catch (Exception exc) {
// nothing to do
}
return retval;
}

First you need to retrieve the BluetoothAdapter:
final BluetoothAdapter btAdapter =
BluetoothAdapter.getDefaultAdapter();
Second you need to make sure Bluetooth is available and turned on :
if (btAdapter != null && btAdapter.isEnabled()) // null means no
Bluetooth!
If the Bluetooth is not turned out you can either use btAdapter.enable() which is not recommended in the documentation or ask the user to do it : Programmatically enabling bluetooth on Android
Third you need to define an array of states (to filter out
unconnected devices):
final int[] states = new int[] {BluetoothProfile.STATE_CONNECTED,
BluetoothProfile.STATE_CONNECTING};
Fourth, you create a BluetoothProfile.ServiceListener which
contains two callbacks triggered when a service is connected and
disconnected :
final BluetoothProfile.ServiceListener listener = new BluetoothProfile.ServiceListener() {
#Override
public void onServiceConnected(int profile, BluetoothProfile proxy) {
}
#Override
public void onServiceDisconnected(int profile) {
}
};
Now since you have to repeat the querying process for all available Bluetooth Profiles in the Android SDK (A2Dp, GATT, GATT_SERVER, Handset, Health, SAP) you should proceed as follow :
In onServiceConnected, place a condition that check what is the current profile so that we add the found devices into the correct collection and we use : proxy.getDevicesMatchingConnectionStates(states) to filter out unconnected devices:
switch (profile) {
case BluetoothProfile.A2DP:
ad2dpDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
case BluetoothProfile.GATT: // NOTE ! Requires SDK 18 !
gattDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
case BluetoothProfile.GATT_SERVER: // NOTE ! Requires SDK 18 !
gattServerDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
case BluetoothProfile.HEADSET:
headsetDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
case BluetoothProfile.HEALTH: // NOTE ! Requires SDK 14 !
healthDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
case BluetoothProfile.SAP: // NOTE ! Requires SDK 23 !
sapDevices.addAll(proxy.getDevicesMatchingConnectionStates(states));
break;
}
And finally, the last thing to do is start the querying process :
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.A2DP);
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.GATT); // NOTE ! Requires SDK 18 !
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.GATT_SERVER); // NOTE ! Requires SDK 18 !
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.HEADSET);
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.HEALTH); // NOTE ! Requires SDK 14 !
btAdapter.getProfileProxy(yourContext, listener, BluetoothProfile.SAP); // NOTE ! Requires SDK 23 !
source: https://stackoverflow.com/a/34790442/2715054

So you get the list of paired devices.
BluetoothAdapter btAdapter = BluetoothAdapter.getDefaultAdapter();
Set<BluetoothDevice> pairedDevicesList = btAdapter.getBondedDevices();
for (BluetoothDevice pairedDevice : pairedDevicesList) {
Log.d("BT", "pairedDevice.getName(): " + pairedDevice.getName());
Log.d("BT", "pairedDevice.getAddress(): " + pairedDevice.getAddress());
saveValuePreference(getApplicationContext(), pairedDevice.getName(), pairedDevice.getAddress());
}

Android system doesn't let you query for all "currently" connected devices. It however, you can query for paired devices. You will need to use a broadcast receiver to listen to ACTION_ACL_{CONNECTED|DISCONNECTED} events along with STATE_BONDED event to update your application states to track what's currently connected.

I found a solution and it works on android 10
Kotlin
private val serviceListener: ServiceListener = object : ServiceListener {
var name: String? = null
var address: String? = null
var threadName: String? = null
override fun onServiceDisconnected(profile: Int) {}
override fun onServiceConnected(profile: Int, proxy: BluetoothProfile) {
for (device in proxy.connectedDevices) {
name = device.name
address = device.address
threadName = Thread.currentThread().name
Toast.makeText(
this#MainActivity,
"$name $address$threadName",
Toast.LENGTH_SHORT
).show()
Log.i(
"onServiceConnected",
"|" + device.name + " | " + device.address + " | " + proxy.getConnectionState(
device
) + "(connected = "
+ BluetoothProfile.STATE_CONNECTED + ")"
)
}
BluetoothAdapter.getDefaultAdapter().closeProfileProxy(profile, proxy)
}
}
Call this method in main thread
BluetoothAdapter.getDefaultAdapter()
.getProfileProxy(this, serviceListener, BluetoothProfile.HEADSET)
Java
original code

Please analyze this class online.
Here you will find how to discover all connected (paired) Bluetooth devices.

Well here are the steps:
First, you start intent to discover devices
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
Register a broadcast reciver for it:
registerReceiver(mReceiver, filter);
On the definition of mReceiver:
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
// Add the name and address to an array adapter to show in a ListView
arrayadapter.add(device.getName())//arrayadapter is of type ArrayAdapter<String>
lv.setAdapter(arrayadapter); //lv is the list view
arrayadapter.notifyDataSetChanged();
}
}
and the list will be automatically populated on new device discovery.