Develop Reference

Connect to BLE device

So I've made this app, where I find all BLE Devices with a name. But how can I make one of the specific fields, clickable and automatic connect to the device, so I can start writing/reading from it?
Adapter
public class ListAdapter_BTLE_Devices extends ArrayAdapter<BTLE_Device> {
Activity activity;
int layoutResourceID;
ArrayList<BTLE_Device> devices;
public ListAdapter_BTLE_Devices(Activity activity, int resource, ArrayList<BTLE_Device> objects) {
super(activity.getApplicationContext(), resource, objects);
this.activity = activity;
layoutResourceID = resource;
devices = objects;
}
#Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
LayoutInflater inflater =
(LayoutInflater) activity.getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(layoutResourceID, parent, false);
}
BTLE_Device device = devices.get(position);
String name = device.getName();
String address = device.getAddress();
int rssi = device.getRSSI();
TextView BLE_name = (TextView) convertView.findViewById(R.id.BLE_name);
if (name != null && name.length() > 0) {
BLE_name.setText(device.getName());
}
else {
BLE_name.setText("No Name");
}
TextView BLE_rssi = (TextView) convertView.findViewById(R.id.BLE_rssi);
BLE_rssi.setText("RSSI: " + Integer.toString(rssi));
TextView BLE_macaddr = (TextView) convertView.findViewById(R.id.BLE_macaddr);
if (address != null && address.length() > 0) {
BLE_macaddr.setText("MAC-addr: "+device.getAddress());
}
else {
BLE_macaddr.setText("No Address");
}
return convertView;
}
}
EDIT
I think i might be connected to the GATT now, so what I've done is..
To start with i get the MAC-addr from the Mainactivity and then I saved it in a intent, and started another activity onclick.
Here I did the follwing
DeviceAddress = intent.getStringExtra(MainActivity.EXTRAS_BLE_ADDRESS);
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(DeviceAddress);
device.connectGatt(this, false, mGattCallback);
and when I call connectGatt it prints the message Log.d(TAG, "Connection State: 1");, is this the right way to do it?
private BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
#RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN_MR2)
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.d(TAG, "Connection State Change: "+status+" -> "+connectionState(newState));
if (status == BluetoothGatt.GATT_SUCCESS && newState == BluetoothProfile.STATE_CONNECTED) {
/*
* Once successfully connected, we must next discover all the services on the
* device before we can read and write their characteristics.
*/
Log.d(TAG, "Connection State: 1");
gatt.discoverServices();
} else if (status == BluetoothGatt.GATT_SUCCESS && newState == BluetoothProfile.STATE_DISCONNECTED) {
/*
* If at any point we disconnect, send a message to clear the weather values
* out of the UI
*/
Log.d(TAG, "Connection State: 2");
} else if (status != BluetoothGatt.GATT_SUCCESS) {
/*
* If there is a failure at any stage, simply disconnect
*/
Log.d(TAG, "Connection State: 3");
gatt.disconnect();
}
}

If you have problems with Bluetooth LE I suggest you to use my bluetooth le library (don't reinvent the wheel, it tooks me about 3/4 months to make the library, a bluetooth le communication can be really tricky to make), it is open source so you can also see the code for having an example of implementation, I link you the github page: https://github.com/niedev/BluetoothCommunicator
For use the library in a project you have to add jitpack.io to your root build.gradle (project):
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
Then add the last version of BluetoothCommunicator to your app build.gradle
dependencies {
implementation 'com.github.niedev:BluetoothCommunicator:1.0.6'
}
To use this library add these permissions to your manifest:
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
Then add android:largeHeap="true" to the application tag in the manifest:
Example
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<application
android:name="com.bluetooth.communicatorexample.Global"
android:allowBackup="true"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:largeHeap="true"
android:theme="#style/Theme.Speech">
<activity android:name="com.bluetooth.communicatorexample.MainActivity"
android:configChanges="orientation|screenSize">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
Once you have downloaded the libray and set the manifest, you need to create a bluetooth communicator object, it is the object that handles all operations of bluetooth low energy library, if you want to manage the bluetooth connections in multiple activities I suggest you to save this object as an attribute of a custom class that extends Application and create a getter so you can access to bluetoothCommunicator from any activity or service with:
((custom class name) getApplication()).getBluetoothCommunicator();
Next step is to initialize bluetoothCommunicator, the parameters are: a context, the name by which the other devices will see us (limited to 18 characters and can be only characters listed in BluetoothTools.getSupportedUTFCharacters(context) because the number of bytes for advertising beacon is limited) and the strategy (for now the only supported stategy is BluetoothCommunicator.STRATEGY_P2P_WITH_RECONNECTION)
bluetoothCommunicator = new BluetoothCommunicator(this, "device name", BluetoothCommunicator.STRATEGY_P2P_WITH_RECONNECTION);
Then add the bluetooth communicator callback, the callback will listen for all events of bluetooth communicator:
bluetoothCommunicator.addCallback(new BluetoothCommunicator.Callback() {
#Override
public void onBluetoothLeNotSupported() {
super.onBluetoothLeNotSupported();
Notify that bluetooth low energy is not compatible with this device
}
#Override
public void onAdvertiseStarted() {
super.onAdvertiseStarted();
Notify that advertise has started, if you want to do something after the start of advertising do it here, because
after startAdvertise there is no guarantee that advertise is really started (it is delayed)
}
#Override
public void onDiscoveryStarted() {
super.onDiscoveryStarted();
Notify that discovery has started, if you want to do something after the start of discovery do it here, because
after startDiscovery there is no guarantee that discovery is really started (it is delayed)
}
#Override
public void onAdvertiseStopped() {
super.onAdvertiseStopped();
Notify that advertise has stopped, if you want to do something after the stop of advertising do it here, because
after stopAdvertising there is no guarantee that advertise is really stopped (it is delayed)
}
#Override
public void onDiscoveryStopped() {
super.onDiscoveryStopped();
Notify that discovery has stopped, if you want to do something after the stop of discovery do it here, because
after stopDiscovery there is no guarantee that discovery is really stopped (it is delayed)
}
#Override
public void onPeerFound(Peer peer) {
super.onPeerFound(peer);
Here for example you can save peer in a list or anywhere you want and when the user
choose a peer you can call bluetoothCommunicator.connect(peer founded) but if you want to
use a peer for connect you have to have peer updated (see onPeerUpdated or onPeerLost), if you use a
non updated peer the connection might fail
instead if you want to immediate connect where peer is found you can call bluetoothCommunicator.connect(peer) here
}
#Override
public void onPeerLost(Peer peer){
super.onPeerLost(peer);
It means that a peer is out of range or has interrupted the advertise,
here you can delete the peer lost from a eventual collection of founded peers
}
#Override
public void onPeerUpdated(Peer peer,Peer newPeer){
super.onPeerUpdated(peer,newPeer);
It means that a founded peer (or connected peer) has changed (name or address or other things),
if you have a collection of founded peers, you need to replace peer with newPeer if you want to connect successfully to that peer.
In case the peer updated is connected and you have saved connected peers you have to update the peer if you want to successfully
send a message or a disconnection request to that peer.
}
#Override
public void onConnectionRequest(Peer peer){
super.onConnectionRequest(peer);
It means you have received a connection request from another device (peer) (that have called connect)
for accept the connection request and start connection call bluetoothCommunicator.acceptConnection(peer);
for refusing call bluetoothCommunicator.rejectConnection(peer); (the peer must be the peer argument of onConnectionRequest)
}
#Override
public void onConnectionSuccess(Peer peer,int source){
super.onConnectionSuccess(peer,source);
This means that you have accepted the connection request using acceptConnection or the other
device has accepted your connection request and the connection is complete, from now on you
can send messages or data (or disconnection request) to this peer until onDisconnected
To send messages to all connected peers you need to create a message with a context, a header, represented by a single character string
(you can use a header to distinguish between different types of messages, or you can ignore it and use a random
character), the text of the message, or a series of bytes if you want to send any kind of data and the peer you want to send the message to
(must be connected to avoid errors), example: new Message(context,"a","hello world",peer);
If you want to send message to a specific peer you have to set the sender of the message with the corresponding peer.
To send disconnection request to connected peer you need to call bluetoothCommunicator.disconnect(peer);
}
#Override
public void onConnectionFailed(Peer peer,int errorCode){
super.onConnectionFailed(peer,errorCode);
This means that your connection request is rejected or has other problems,
to know the cause of the failure see errorCode (BluetoothCommunicator.CONNECTION_REJECTED
means rejected connection and BluetoothCommunicator.ERROR means generic error)
}
#Override
public void onConnectionLost(Peer peer){
super.onConnectionLost(peer);
This means that a connected peer has lost the connection with you and the library is trying
to restore it, in this case you can update the gui to notify this problem.
You can still send messages in this situation, all sent messages are put in a queue
and sent as soon as the connection is restored
}
#Override
public void onConnectionResumed(Peer peer){
super.onConnectionResumed(peer);
Means that connection lost is resumed successfully
}
#Override
public void onMessageReceived(Message message,int source){
super.onMessageReceived(message,source);
Means that you have received a message containing TEXT, for know the sender you can call message.getSender() that return
the peer that have sent the message, you can ignore source, it indicate only if you have received the message
as client or as server
}
#Override
public void onDataReceived(Message data,int source){
super.onDataReceived(data,source);
Means that you have received a message containing DATA, for know the sender you can call message.getSender() that return
the peer that have sent the message, you can ignore source, it indicate only if you have received the message
as client or as server
}
#Override
public void onDisconnected(Peer peer,int peersLeft){
super.onDisconnected(peer,peersLeft);
Means that the peer is disconnected, peersLeft indicate the number of connected peers remained
}
#Override
public void onDisconnectionFailed(){
super.onDisconnectionFailed();
Means that a disconnection is failed, super.onDisconnectionFailed will reactivate bluetooth for forcing disconnection
(however the disconnection will be notified in onDisconnection)
}
});
Finally you can start discovery and/or advertising:
bluetoothCommunicator.startAdvertising();
bluetoothCommunicator.startDiscovery();
All other actions that can be done are explained with the comments in the code of callback I wrote before.

To connect to the Device first you must perform you BLE scan which (if your using the starter code) runs a callback and add it to a list of found devices.
Add a filter in to only allow the set device you are looking for. As BLE advertises a packet upto 31 bytes you should have some data in here which discerns you device such as manufacturer id or data etc. Or if you are working on a simple project you can programmatically hard code in the device address.
Then when this device is discovered from the scan you can stop your BLE scan and automatically queue a connection request. This will ask for the GATT request to be made and therefore, grant you access to the GATT services and thus characteristics on the device.

You can add a view to your holder and set a click listener to it. A view could be a transparent rectangle all around your display card (or whatever you use).
I'd suggest this in depth read regarding BLE usage. On the click listener you can queue up the connection request.

Programmatically pairing with a BLE device on Android 4.4+

Does anyone have a complete working example of how to programmatically pair with a BLE (not Bluetooth Classic) device that uses passkey entry (i.e. a 6-digit PIN) or Numeric Comparison on Android 4.4 or later? By 'programmatically' I mean I tell Android the PIN - the user isn't prompted.
There are many similar questions about this on SO but they are either a) about Bluetooth Classic, b) old (before setPin() and createBond() were public), or c) unanswered.
My understanding is as follows.
You connect to the device and discover its services.
You try to read a 'protected' characteristic.
The device returns an authentication error.
Android somehow initiates pairing and you tell it the PIN.
You can now read the characteristic.
I have created a device using mBed running on the nRF51-DK and given it a single characteristic.
I set up the security parameters like so:
ble.securityManager().init(
true, // Enable bonding (though I don't really need this)
true, // Require MitM protection. I assume you don't get a PIN prompt without this, though I'm not 100% sure.
SecurityManager::IO_CAPS_DISPLAY_ONLY, // This makes it us the Passkey Entry (PIN) pairing method.
"123456"); // Static PIN
And then in the characteristic I used
requireSecurity(SecurityManager::SECURITY_MODE_ENCRYPTION_WITH_MITM);
Now when I try to read it with the Nordic Master Control Panel, I get a pairing request notification like this:
And I can put this PIN in, and then MCP says I'm bonded, and can read the characteristic.
However, in my app I would like to avoid having the user enter the PIN, since I know it already. Does anyone have a complete recent example of how to do this?
Edit: By the way this is the most relevant question I found on SO, but the answer there doesn't seem to work.

I almost have it working. It pairs programmatically but I can't get rid of the "Pairing request" notification. Some answers to this question claim to be able to hide it just after it is shown using the hidden method cancelPairingUserInput() but that doesn't seem to work for me.
Edit: Success!
I eventually resorted to reading the source code of BluetoothPairingRequest and the code that sends the pairing request broadcast and realised I should be intercepting the ACTION_PAIRING_REQUEST. Fortunately it is an ordered intent broadcast so you can intercept it before the system does.
Here's the procedure.
Register to receive BluetoothDevice.ACTION_PAIRING_REQUEST changed broadcast intents. Use a high priority!
Connect to the device.
Discover services.
If you have disconnected by now, it's probably because the bond information is incorrect (e.g. the peripheral purged it). In that case, delete the bond information using a hidden method (seriously Google), and reconnect.
Try to read a characteristic that requires encryption MitM protection.
In the ACTION_PAIRING_REQUEST broadcast receiver, check that the pairing type is BluetoothDevice.PAIRING_VARIANT_PIN and if so, call setPin() and abortBroadcast(). Otherwise you can just let the system handle it, or show an error or whatever.
Here is the code.
/* This implements the BLE connection logic. Things to watch out for:
1. If the bond information is wrong (e.g. it has been deleted on the peripheral) then
discoverServices() will cause a disconnect. You need to delete the bonding information and reconnect.
2. If the user ignores the PIN request, you get the undocumented GATT_AUTH_FAILED code.
*/
public class ConnectActivityLogic extends Fragment
{
// The connection to the device, if we are connected.
private BluetoothGatt mGatt;
// This is used to allow GUI fragments to subscribe to state change notifications.
public static class StateObservable extends Observable
{
private void notifyChanged() {
setChanged();
notifyObservers();
}
};
// When the logic state changes, State.notifyObservers(this) is called.
public final StateObservable State = new StateObservable();
public ConnectActivityLogic()
{
}
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// Tell the framework to try to keep this fragment around
// during a configuration change.
setRetainInstance(true);
// Actually set it in response to ACTION_PAIRING_REQUEST.
final IntentFilter pairingRequestFilter = new IntentFilter(BluetoothDevice.ACTION_PAIRING_REQUEST);
pairingRequestFilter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY - 1);
getActivity().getApplicationContext().registerReceiver(mPairingRequestRecevier, pairingRequestFilter);
// Update the UI.
State.notifyChanged();
// Note that we don't actually need to request permission - all apps get BLUETOOTH and BLUETOOTH_ADMIN permissions.
// LOCATION_COARSE is only used for scanning which I don't need (MAC is hard-coded).
// Connect to the device.
connectGatt();
}
#Override
public void onDestroy()
{
super.onDestroy();
// Disconnect from the device if we're still connected.
disconnectGatt();
// Unregister the broadcast receiver.
getActivity().getApplicationContext().unregisterReceiver(mPairingRequestRecevier);
}
// The state used by the UI to show connection progress.
public ConnectionState getConnectionState()
{
return mState;
}
// Internal state machine.
public enum ConnectionState
{
IDLE,
CONNECT_GATT,
DISCOVER_SERVICES,
READ_CHARACTERISTIC,
FAILED,
SUCCEEDED,
}
private ConnectionState mState = ConnectionState.IDLE;
// When this fragment is created it is given the MAC address and PIN to connect to.
public byte[] macAddress()
{
return getArguments().getByteArray("mac");
}
public int pinCode()
{
return getArguments().getInt("pin", -1);
}
// Start the connection process.
private void connectGatt()
{
// Disconnect if we are already connected.
disconnectGatt();
// Update state.
mState = ConnectionState.CONNECT_GATT;
State.notifyChanged();
BluetoothDevice device = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(macAddress());
// Connect!
mGatt = device.connectGatt(getActivity(), false, mBleCallback);
}
private void disconnectGatt()
{
if (mGatt != null)
{
mGatt.disconnect();
mGatt.close();
mGatt = null;
}
}
// See https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/master/stack/include/gatt_api.h
private static final int GATT_ERROR = 0x85;
private static final int GATT_AUTH_FAIL = 0x89;
private android.bluetooth.BluetoothGattCallback mBleCallback = new BluetoothGattCallback()
{
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState)
{
super.onConnectionStateChange(gatt, status, newState);
switch (newState)
{
case BluetoothProfile.STATE_CONNECTED:
// Connected to the device. Try to discover services.
if (gatt.discoverServices())
{
// Update state.
mState = ConnectionState.DISCOVER_SERVICES;
State.notifyChanged();
}
else
{
// Couldn't discover services for some reason. Fail.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
}
break;
case BluetoothProfile.STATE_DISCONNECTED:
// If we try to discover services while bonded it seems to disconnect.
// We need to debond and rebond...
switch (mState)
{
case IDLE:
// Do nothing in this case.
break;
case CONNECT_GATT:
// This can happen if the bond information is incorrect. Delete it and reconnect.
deleteBondInformation(gatt.getDevice());
connectGatt();
break;
case DISCOVER_SERVICES:
// This can also happen if the bond information is incorrect. Delete it and reconnect.
deleteBondInformation(gatt.getDevice());
connectGatt();
break;
case READ_CHARACTERISTIC:
// Disconnected while reading the characteristic. Probably just a link failure.
gatt.close();
mState = ConnectionState.FAILED;
State.notifyChanged();
break;
case FAILED:
case SUCCEEDED:
// Normal disconnection.
break;
}
break;
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status)
{
super.onServicesDiscovered(gatt, status);
// Services have been discovered. Now I try to read a characteristic that requires MitM protection.
// This triggers pairing and bonding.
BluetoothGattService nameService = gatt.getService(UUIDs.NAME_SERVICE);
if (nameService == null)
{
// Service not found.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
return;
}
BluetoothGattCharacteristic characteristic = nameService.getCharacteristic(UUIDs.NAME_CHARACTERISTIC);
if (characteristic == null)
{
// Characteristic not found.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
return;
}
// Read the characteristic.
gatt.readCharacteristic(characteristic);
mState = ConnectionState.READ_CHARACTERISTIC;
State.notifyChanged();
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status)
{
super.onCharacteristicRead(gatt, characteristic, status);
if (status == BluetoothGatt.GATT_SUCCESS)
{
// Characteristic read. Check it is the right one.
if (!UUIDs.NAME_CHARACTERISTIC.equals(characteristic.getUuid()))
{
// Read the wrong characteristic. This shouldn't happen.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
return;
}
// Get the name (the characteristic I am reading just contains the device name).
byte[] value = characteristic.getValue();
if (value == null)
{
// Hmm...
}
disconnectGatt();
mState = ConnectionState.SUCCEEDED;
State.notifyChanged();
// Success! Save it to the database or whatever...
}
else if (status == BluetoothGatt.GATT_INSUFFICIENT_AUTHENTICATION)
{
// This is where the tricky part comes
if (gatt.getDevice().getBondState() == BluetoothDevice.BOND_NONE)
{
// Bonding required.
// The broadcast receiver should be called.
}
else
{
// ?
}
}
else if (status == GATT_AUTH_FAIL)
{
// This can happen because the user ignored the pairing request notification for too long.
// Or presumably if they put the wrong PIN in.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
}
else if (status == GATT_ERROR)
{
// I thought this happened if the bond information was wrong, but now I'm not sure.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
}
else
{
// That's weird.
disconnectGatt();
mState = ConnectionState.FAILED;
State.notifyChanged();
}
}
};
private final BroadcastReceiver mPairingRequestRecevier = new BroadcastReceiver()
{
#Override
public void onReceive(Context context, Intent intent)
{
if (BluetoothDevice.ACTION_PAIRING_REQUEST.equals(intent.getAction()))
{
final BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
int type = intent.getIntExtra(BluetoothDevice.EXTRA_PAIRING_VARIANT, BluetoothDevice.ERROR);
if (type == BluetoothDevice.PAIRING_VARIANT_PIN)
{
device.setPin(Util.IntToPasskey(pinCode()));
abortBroadcast();
}
else
{
L.w("Unexpected pairing type: " + type);
}
}
}
};
public static void deleteBondInformation(BluetoothDevice device)
{
try
{
// FFS Google, just unhide the method.
Method m = device.getClass().getMethod("removeBond", (Class[]) null);
m.invoke(device, (Object[]) null);
}
catch (Exception e)
{
L.e(e.getMessage());
}
}
}

I also faced the same problem and after all the research, I figured out the below solution to pair to a BLE without any manual intervention.
(Tested and working!!!)
I am basically looking for a particular Bluetooth device (I know MAC address) and pair with it once found. The first thing to do is to create pair request using a broadcast receiver and handle the request as below.
IntentFilter intentFilter = new IntentFilter(BluetoothDevice.ACTION_PAIRING_REQUEST);
intentFilter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
registerReceiver(broadCastReceiver,intentFilter);
You need to write the broadcastReceiver and handle it as below.
String BLE_PIN = "1234"
private BroadcastReceiver broadCastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if(BluetoothDevice.ACTION_PAIRING_REQUEST.equals(action))
{
BluetoothDevice bluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
bluetoothDevice.setPin(BLE_PIN.getBytes());
Log.e(TAG,"Auto-entering pin: " + BLE_PIN);
bluetoothDevice.createBond();
Log.e(TAG,"pin entered and request sent...");
}
}
};
Voila! You should be able to pair to Bluetooth device without ANY MANUAL INTERVENTION.
Hope this helps :-) Please make it right answer if it works for you.

Android BLE - Connecting to multiple devices at once

I am developing an Android Application that connects to a BLE Device and reads the Gatt Services and Gatt Characteristics. I used the BluetoothLeGatt sample project from the Android Development Site as my reference.
So far, I am able to programmatically connect to a device (I took note of my Device's Address to be able to do this) and filter out the specific Gatt Service I want to read and that Services' specific Characteristics by taking note of the UUID of both the Service and the Characteristics. The sample provided by Google also updates whenever there's a message sent from my BLE Device to my Android Application. Overall, I have no problems at this end.
However, upon reading up further on GATT, I found that it is possible to connect to multiple BLE devices (all slaves OR servers - being the ones that send the data) using a single Android Application (as master OR client - as the one who receives said data). So what I tried to do was to have 2 BLE Devices (different Address), took note of their Address, and then my application tries to connect to them once the application sees that those 2 addresses are up and running.
In code, I call this function when I see my 2 BLE Devices:
private void connectToDevice(){
mDeviceName = deviceList.get(currentIndex).getName();
mDeviceAddress = deviceList.get(currentIndex).getAddress();
Log.e(TAG, "connecting to device name = " + mDeviceName);
mBluetoothLeService.connect(mDeviceAddress);
}
Where currentIndex is initially set to zero. Then once I get a successful connection, I do:
private final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
Log.e(TAG, "connected");
mConnected = true;
if(currentIndex < deviceList.size()-1) currentIndex ++;
connectToDevice();
}
}
};
Where I check if I still have devices to connect to in my deviceList, if so, increment my counter and then connect until I exhaust everything in my list.
However, I seem to have no success at all using this method.
Kindly note that switching connection (round robin) between my devices isn't an option. This will be an issue when I have a lot of devices and it's important to get their messages real time without delays. This said, I have to have a live connection to my devices.
Has anyone tried to connect to multiple BLE Devices in Android? I'm not sure on how to proceed on this.

Indeed it is possible to connect to more than one peripheral from your Android device. However, it will make your code much more complex since you will need to manage each connection and responses.
For each connection you would have to implement a BluetoothGatt with it's callbacks. I tested it many months ago with a dummy test and as I said, it worked well and I was able to connect to different peripherals. However, if you chain many commands there seem to be some overlapping issues described in this thread.

As asked here is the relevant code : (Here the ArrayList contains the founded peripheral devices)
for(int i=0;i< Utility.selectedDeviceList.size();i++) {
Log.d(Utility.TAG,"state"+ Utility.selectedDeviceList.get(i).getmConnectionState());
if (Utility.selectedDeviceList.get(i).getmConnectionState() != Utility.CONNECTED) {
Log.d(Utility.TAG,"Connecting LeSerive::" + Utility.selectedDeviceList.get(i).getAddress());
Utility.mBluetoothLeService.connect(i, Utility.selectedDeviceList.get(i).getAddress());
}
}
This for loop is a part of runnable interface which is called inside a handler having a looper.
public void run() {
Looper.prepare();
Looper mLooper = Looper.myLooper();
Log.d(Utility.TAG,"BLE Thread Started::");
mHandler = new Handler(mLooper) {
#Override
public void handleMessage(Message msg) {
switch (msg.what) {
case Utility.BLE_SYNC:
Log.d(Utility.TAG,"BLE Sync Connecting::");
mHandler.post(SynState);
break;
}
};
Looper.loop();
}
I used this approach because their is lot of communication between peripherals to send and receive the data from them.
This is the connect method which inside a Service :
public boolean connect(int tag,final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w(Utility.TAG, "BluetoothAdapter not initialized or unspecified address.");
return false;
}
Utility.selectedDeviceList.get(tag).setmConnectionState(Utility.CONNECTING);
if( Utility.selectedDeviceList.get(tag).getmBluetoothGatt()==null){
Log.w(Utility.TAG, "new connect :: "+ Utility.selectedDeviceList.get(tag).getAddress());
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w(Utility.TAG, "Device not found. Unable to connect.");
return false;
}
try {
Utility.selectedDeviceList.get(tag).setmBluetoothGatt(device.connectGatt(this, false, mGattCallback));
}
catch (Exception e)
{
e.printStackTrace();
Log.d(Utility.TAG,"ConnectGatt exception caught");
}
}
return true;
}
This is the mGattCallBack :
private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.d(Utility.TAG, "onServicesDiscovered");
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic,int status) {
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicWrite(gatt, characteristic, status);
Log.d(Utility.TAG,">>onCharacteristicWrite");
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic) {
}
};
Hope it clears few things for you

It is possible to connect to multiple devices at a time. in my experience it works pretty stable and the number of devices you can connect to (stable) depends on your hardware. I found out that best practise (for me) was to create one separate service for the scanning stuff and one service for each Bluetoothconnection. it's important not to use bound services because the termination of a connection is not stible when binding to it.
With this pattern you can control your connection easily. To transport data out of your service you can use a broadcastreceiver, for example if you want to display the data in your main activity. Termination of the connection is pretty important so stop the service and in onDestroy call
mConnectedGatt.disconnect();
ble_device=null;
For the Scanning part I've used a List of Strings where I saved all the mac Adresses I want to find. When i found one device I deleted it from the list and if the list is empty it stopped the scanner service. To transmit my found device I used a broadcastreceiver and sent it to my main Activity. There I transmitted it to the right service.
Hope this helps

How to detect bluetooth headset connection in Android

I tried example code google refers as below to detect connected bluetooth devices
BluetoothHeadset mBluetoothHeadset;
// Get the default adapter
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
// Establish connection to the proxy.
mBluetoothAdapter.getProfileProxy(context, mProfileListener, BluetoothProfile.HEADSET);
private BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() {
public void onServiceConnected(int profile, BluetoothProfile proxy) {
if (profile == BluetoothProfile.HEADSET) {
mBluetoothHeadset = (BluetoothHeadset) proxy;
}
}
public void onServiceDisconnected(int profile) {
if (profile == BluetoothProfile.HEADSET) {
mBluetoothHeadset = null;
}
}
};
// ... call functions on mBluetoothHeadset
But I got the following problems:
mBluetoothHeadset is only available inside onServiceConnected. I use getConnectedDevices to detect live bluetooth headset. but if I place the code below
List ConnectedDevices = mBluetoothHeadset.getConnectedDevices();
out of onServiceConnected, running program lead always crash. What's wrong here?
is there any possibility to use mBluetoothHeadset value outside onServiceConnected ? like the example show? Or May I trans some parameter/value from onServiceConnected to outside?
Actually the example codes don't work. i have to place additional code after mProfileListener:
if (mBluetoothAdapter.getProfileProxy(this, mProfileListener,BluetoothProfile.HEADSET)==false) { ....
What's the reason? or what's wrong with my code?
From system log the code seems work, but when I run it, program stay in onServiceConnected, never go to onServiceDisconnected, or outside if no other action the user perform(e.g press a confirm button). What's wrong?

Android Bluetooth Low Energy Pairing

How to pair a Bluetooth Low Energy(BLE) device with Android to read encrypted data.
Using the information in the Android BLE page, I am able to discover the device, connect to it, discover services and read un-encrypted characteristics.
When I try to read an encrypted characteristic (one that will cause iOS to show a popup asking to pair and then complete the read) I am getting an error code 5, which corresponds to Insufficient Authentication.
I am not sure how to get the device paired or how to provide the authentication information for the read to complete.
I toyed with BluetoothGattCharacteristics by trying to add descriptors, but that did not work either.
Any help is appreciated!

When you get the GATT_INSUFFICIENT_AUTHENTICATION error, the system starts the bonding process for you. In the example below I'm trying to enable notifications and indications on glucose monitor. First I'm enabling the notifications on Glucose Measurement characteristic which can cause the error to appear.
#Override
public void onDescriptorWrite(BluetoothGatt gatt, BluetoothGattDescriptor descriptor, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
if (GM_CHARACTERISTIC.equals(descriptor.getCharacteristic().getUuid())) {
mCallbacks.onGlucoseMeasurementNotificationEnabled();
if (mGlucoseMeasurementContextCharacteristic != null) {
enableGlucoseMeasurementContextNotification(gatt);
} else {
enableRecordAccessControlPointIndication(gatt);
}
}
if (GM_CONTEXT_CHARACTERISTIC.equals(descriptor.getCharacteristic().getUuid())) {
mCallbacks.onGlucoseMeasurementContextNotificationEnabled();
enableRecordAccessControlPointIndication(gatt);
}
if (RACP_CHARACTERISTIC.equals(descriptor.getCharacteristic().getUuid())) {
mCallbacks.onRecordAccessControlPointIndicationsEnabled();
}
} else if (status == BluetoothGatt.GATT_INSUFFICIENT_AUTHENTICATION) {
// this is where the tricky part comes
if (gatt.getDevice().getBondState() == BluetoothDevice.BOND_NONE) {
mCallbacks.onBondingRequired();
// I'm starting the Broadcast Receiver that will listen for bonding process changes
final IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_BOND_STATE_CHANGED);
mContext.registerReceiver(mBondingBroadcastReceiver, filter);
} else {
// this situation happens when you try to connect for the second time to already bonded device
// it should never happen, in my opinion
Logger.e(TAG, "The phone is trying to read from paired device without encryption. Android Bug?");
// I don't know what to do here
// This error was found on Nexus 7 with KRT16S build of Andorid 4.4. It does not appear on Samsung S4 with Andorid 4.3.
}
} else {
mCallbacks.onError(ERROR_WRITE_DESCRIPTOR, status);
}
};
Where the mBondingBroadcastReceiver is:
private BroadcastReceiver mBondingBroadcastReceiver = new BroadcastReceiver() {
#Override
public void onReceive(final Context context, final Intent intent) {
final BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
final int bondState = intent.getIntExtra(BluetoothDevice.EXTRA_BOND_STATE, -1);
final int previousBondState = intent.getIntExtra(BluetoothDevice.EXTRA_PREVIOUS_BOND_STATE, -1);
Logger.d(TAG, "Bond state changed for: " + device.getAddress() + " new state: " + bondState + " previous: " + previousBondState);
// skip other devices
if (!device.getAddress().equals(mBluetoothGatt.getDevice().getAddress()))
return;
if (bondState == BluetoothDevice.BOND_BONDED) {
// Continue to do what you've started before
enableGlucoseMeasurementNotification(mBluetoothGatt);
mContext.unregisterReceiver(this);
mCallbacks.onBonded();
}
}
};
Remember to unregister the broadcast receiver when exiting the activity. It may have not been unregistered by the receicver itself.

You might need to check the Kernel smp.c file, which method of paring it invoke for paring. 1) passkey 2)Just work or etc . i guess if it will be able to invoke MIMT and passkey level of security , there will not be any authentication issue. Make sure all flags is set to invoke the SMP passkey methods. track by putting some print in smp.c file.
A solution which works in ICS : with btmgmt tool in android and hooking it in encryption APIs. with passkey or any other methods. it works. You might need to add the passkey APIs in btmgmt from latest bluez code.

i think new android 4.4 provide pairing method. same problem already i am facing so wait for update and hope over problem solved createBond() method .
http://developer.android.com/reference/android/bluetooth/BluetoothDevice.html#setPairingConfirmation%28boolean%29