Android Bluetooth Low Energy (BLE) - cooking it right, part # 4 (bonding)

Content

Part # 1 (scanning)

Part # 2 (connecting / disconnecting)

Part # 3 (read / write)

Part # 4 (bonding), you are here

In the  previous article,  we figured out the read / write operations, enable / disable notifications and queue commands. In this article we will talk about  pairing devices  ( Note of the translator - further I will use the term "bonding" ).

Bonding

Some devices require bonding to function properly. Technically, this means that encryption keys are generated, exchanged and stored, for secure data exchange. When starting the bonding procedure, Android may ask the user for consent, pin code or passphrase. On next connections, Android already knows that the device is paired and encryption keys are exchanged secretly without user intervention. Using bonding makes the connection to the device more secure because the connection is encrypted.

bonding Google, , bonding.  createBond()



. , iOS  CoreBluetooth



  !  createBond()



? , , bonding, . Bluetooth , – bonding. . , , , .

bonding:

• Android bonding. Android bonding , , bonding, / .  createBond()
  
  
  
    (. : , - . , Samsung -, );

  
  
  
  
  

• , bonding.  / , . Android bonding;

  
  
  
  
  

• bonding.  bonding , ;

  
  
  
  
  

• , ,    createBond()
  
  
  
    bonding . .

  
  
  
  
  

bonding?

, bonding:

1. , , bonding, ;

   
   
   
   
   

2. «» .  , bonding. / , bonding – /  INSUFFICIENT_AUTHENTICATION
   
   
   
   . iOS.

   
   
   
   
   

3.   bonding    createBond()
   
   
   
   . , iOS, . Bluetooth .

   
   
   
   
   

.

Bonding

bonding ,  onConnectionStateChange



  bonding  BOND_BONDING



. bonding   ,  discoverServices()



, bonding ! .  onConnectionStateChanged



:

// Take action depending on the bond state
if(bondstate == BOND_NONE || bondstate == BOND_BONDED) {
    // Connected to device, now proceed to discover it's services
    ... 
} else if (bondstate == BOND_BONDING) {
    // Bonding process has already started let it complete
    Log.i(TAG, "waiting for bonding to complete");
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, bonding,  BroadcastReceiver



   ACTION_BOND_STATE_CHANGED



   connectGatt



. bonding.

context.registerReceiver(bondStateReceiver, 
                        new IntentFilter(ACTION_BOND_STATE_CHANGED));
private final BroadcastReceiver bondStateReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();
        final BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);

        // Ignore updates for other devices
        if (bluetoothGatt == null || !device.getAddress().equals(bluetoothGatt.getDevice().getAddress()))
            return;

        // Check if action is valid
        if(action == null) return;

        // Take action depending on new bond state
        if (action.equals(ACTION_BOND_STATE_CHANGED)) {
            final int bondState = intent.getIntExtra(EXTRA_BOND_STATE, ERROR);
            final int previousBondState = intent.getIntExtra(BluetoothDevice.EXTRA_PREVIOUS_BOND_STATE, -1);

            switch (bondState) {
                case BOND_BONDING:
                    // Bonding started
                    ...
                    break;
                case BOND_BONDED:
                    // Bonding succeeded
                    ...
                    break;
                case BOND_NONE:
                    // Oh oh
                    ...
                    break;
            }
        }
    }
};
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

bonding, (service discovery), , :

case BOND_BONDED:
    // Bonding succeeded
    Log.d(TAG, "bonded");

    // Check if there are services
    if(bluetoothGatt.getServices().isEmpty()) {
        // No services discovered yet
        bleHandler.post(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, String.format("discovering services of '%s'", getName()));
                boolean result = bluetoothGatt.discoverServices();
                if (!result) {
                    Log.e(TAG, "discoverServices failed to start");
                }
            }
        });
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, bonding .

Bonding /

bonding / , /  GATT_INSUFFICIENT_AUTHENTICATION



. Android-6, 7  onCharacteristicRead



/onCharacteristicWrite



, bonding Android. Android-8 Android bonding. Android-6, 7 / . , bonding.

, :

public void onCharacteristicRead(BluetoothGatt gatt, final BluetoothGattCharacteristic characteristic, int status) {
    // Perform some checks on the status field
    if (status != GATT_SUCCESS) {
        if (status == GATT_INSUFFICIENT_AUTHENTICATION ) {
            // Characteristic encrypted and needs bonding,
            // So retry operation after bonding completes
            // This only happens on Android 5/6/7
            Log.w(TAG, "read needs bonding, bonding in progress");
            return;
        } else {
            Log.e(TAG, String.format(Locale.ENGLISH,"ERROR: Read failed for characteristic: %s, status %d", characteristic.getUuid(), status));
            completedCommand();
            return;
        }
    }
...
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

bonding , :

case BOND_BONDED:
    // Bonding succeeded
    Log.d(TAG, "bonded");

    // Check if there are services
    ...
    // If bonding was triggered by a read/write, we must retry it
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
        if (commandQueueBusy && !manuallyBonding) {
            bleHandler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    Log.d(TAG, "retrying command after bonding");
                    retryCommand();
                }
            }, 50);
        }
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

bonding

,  createBond



 , , . , ? iOS  createBond()



, – bonding , iOS. iOS. BLE ,  createBond()



  - .

 createBond



 , , bonding  BroadcastReceiver



  . (bonding ),  createBond()



  , bonding .

 createBond()



  – .  BluetoothDevice



  MAC-, (bonding). … ! (. : , , , ).

bonding

Android, Bluetooth . , bonding .

.

, bonding . ,  removeBond()



, Java:

try {
    Method method = device.getClass().getMethod("removeBond", (Class[]) null);
    result = (boolean) method.invoke(device, (Object[]) null);
    if (result) {
        Log.i(TAG, "Successfully removed bond");
    }
    return result;
} catch (Exception e) {
    Log.e(TAG, "ERROR: could not remove bond");
    e.printStackTrace();
    return false;
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

bonding

BLE bonding . , bonding :

• bonding

  
  
  
  
  

• B bonding

  
  
  
  
  

• , bonding .

  
  
  
  
  

bonding BOND_NONE



   BroadcastReceiver



. bonding, :

case BOND_NONE:
    if(previousBondState == BOND_BONDING) {
       // Bonding failed
       ...
    } else {
       // Bond lost
       ...
    }
    disconnect();
    break;
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

bonding, , . , Android bonding. .

, . bonding,     , Bluetooth . bonding, Android , , . .

Pairing

. : «pairing», «» - .

Android bonding, . «», (. : Samsung-S9, Android-10, , , , ). Google ( , Android ), .

Pairing :

• ;

  
  
  
  
  

• ;

  
  
  
  
  

• « »;

  
  
  
  
  

• Bluetooth .

  
  
  
  
  

«»   60 . ,   . , , . , . UI -! () ! Samsung - ( JustWorks) , . PIN- . . !

, , , . , . :

public void startPairingPopupHack() {
    String manufacturer = Build.MANUFACTURER;
    if(!manufacturer.equals("samsung")) {
        bluetoothAdapter.startDiscovery();

        callBackHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "popup hack completed");
                bluetoothAdapter.cancelDiscovery();
            }
        }, 1000);
    }
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

– BLE . .

, bonding !

…

BLE Android (. : -, BLE Android, ). BLE . BLE, . !

Can't wait to work with BLE? Try  my Blessed for Android library . It takes all the approaches in this article series and makes it easy to work with BLE in your application.