Subscribe to a BLE Gatt notification Android
I´m developing an BLE app, based on the Gatt sample project provided by google: https://developer.android.com/samples/BluetoothLeGatt/index.html. So, I can send data writing in a characteristic successfully. Now I need to know when this characteristic change its value. I understand that I need to implement the setCharacteristicNotification() method and the onDescriptorWrite() method. But I cant do that this works. Searching, I found some ideas about that: Android BLE API: GATT Notification not received, What are the steps to get notified by Bluetooth Low Energy (BLE) device?, but still no luck I dont understand how it works, what parameter I need define or what I need to do!!!. Some good soul can share me a complete project that do this. All that I need is visualize the value of the characteristic when the BLE device returns some data.
I read the official Android documentation, but it is not so specific about that. Thanks in advance
These are my codes:
Device
public class DeviceControlActivity extends Activity {
public static final String EXTRAS_DEVICE_NAME = "DEVICE_NAME";
public static final String EXTRAS_DEVICE_ADDRESS = "DEVICE_ADDRESS";
private TextView mConnectionState;
private TextView mDataField;
private TextView mRssiField;
private String mDeviceName;
private String mDeviceAddress;
private ExpandableListView mGattServicesList;
private BluetoothLeService mBluetoothLeService;
static ArrayList<ArrayList<BluetoothGattCharacteristic>> mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
private boolean mConnected = false;
private BluetoothGattCharacteristic mNotifyCharacteristic;
private BluetoothGattCharacteristic mWriteCharacteristic, mReadCharacteristic;
Button Escritor;
byte hello[] = { 0 };
private final String LIST_NAME = "NAME";
private final String LIST_UUID = "UUID";
// BluetoothGattCharacteristic characteristic;
// public BluetoothGatt mBluetoothGatt;
// Code to manage Service lifecycle.
private final ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder service) {
mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
if (!mBluetoothLeService.initialize()) {
Log.e("Unable to initialize Bluetooth");
finish();
}
// Automatically connects to the device upon successful start-up
// initialization.
mBluetoothLeService.connect(mDeviceAddress);
mBluetoothLeService.setBLEServiceCb(mDCServiceCb);
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mBluetoothLeService = null;
}
};
// If a given GATT characteristic is selected, check for supported features.
// This sample
// demonstrates 'Read' and 'Notify' features. See
// http://d.android.com/reference/android/bluetooth/BluetoothGatt.html for
// the complete
// list of supported characteristic features.
private final ExpandableListView.OnChildClickListener servicesListClickListner = new ExpandableListView.OnChildClickListener() {
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
@Override
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
if (mGattCharacteristics != null) {
final BluetoothGattCharacteristic characteristic = mGattCharacteristics.get(groupPosition).get(childPosition);
final int charaProp = characteristic.getProperties();
if ((charaProp & BluetoothGattCharacteristic.PROPERTY_READ) > 0) {
// If there is an active notification on a characteristic,
// clear
// it first so it doesn't update the data field on the user
// interface.
Log.d("BluetoothGattCharacteristic has PROPERTY_READ, so send read request");
if (mNotifyCharacteristic != null) {
mBluetoothLeService.setCharacteristicNotification(mNotifyCharacteristic, true);
mNotifyCharacteristic = null;
}
mBluetoothLeService.readCharacteristic(characteristic);
/*Toast.makeText(getApplicationContext(), "Leyó Algo",
Toast.LENGTH_SHORT).show();*/
}
if ((charaProp & BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
Log.d("BluetoothGattCharacteristic has PROPERTY_NOTIFY, so send notify request");
mNotifyCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(characteristic, true);
}
if (((charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE) | (charaProp & BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE)) > 0) {
Log.d("BluetoothGattCharacteristic has PROPERY_WRITE | PROPERTY_WRITE_NO_RESPONSE");
mWriteCharacteristic = characteristic;
// popup an dialog to write something.
showCharactWriteDialog();
}
return true;
}
return false;
}
};
private void showCharactWriteDialog() {
DialogFragment newFrame = new BleCharacterDialogFragment();
newFrame.show(getFragmentManager(), "blewrite");
}
private void clearUI() {
mGattServicesList.setAdapter((SimpleExpandableListAdapter) null);
mDataField.setText(R.string.no_data);
}
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gatt_services_characteristics);
final Intent intent = getIntent();
mDeviceName = intent.getStringExtra(EXTRAS_DEVICE_NAME);
mDeviceAddress = intent.getStringExtra(EXTRAS_DEVICE_ADDRESS);
// Sets up UI references.
((TextView) findViewById(R.id.device_address)).setText(mDeviceAddress);
mGattServicesList = (ExpandableListView) findViewById(R.id.gatt_services_list);
mGattServicesList.setOnChildClickListener(servicesListClickListner);
mConnectionState = (TextView) findViewById(R.id.connection_state);
mDataField = (TextView) findViewById(R.id.data_value);
mRssiField = (TextView) findViewById(R.id.signal_rssi);
getActionBar().setTitle(mDeviceName);
getActionBar().setDisplayHomeAsUpEnabled(true);
Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);
}
@Override
protected void onResume() {
super.onResume();
// registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());
if (mBluetoothLeService != null) {
final boolean result = mBluetoothLeService.connect(mDeviceAddress);
Log.d("Connect request result=" + result);
}
}
@Override
protected void onPause() {
super.onPause();
// unregisterReceiver(mGattUpdateReceiver);
}
@Override
protected void onDestroy() {
super.onDestroy();
unbindService(mServiceConnection);
mBluetoothLeService = null;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.gatt_services, menu);
if (mConnected) {
menu.findItem(R.id.menu_connect).setVisible(false);
menu.findItem(R.id.menu_disconnect).setVisible(true);
} else {
menu.findItem(R.id.menu_connect).setVisible(true);
menu.findItem(R.id.menu_disconnect).setVisible(false);
}
return true;
}
@TargetApi(Build.VERSION_CODES.ECLAIR)
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_connect:
mBluetoothLeService.connect(mDeviceAddress);
return true;
case R.id.menu_disconnect:
mBluetoothLeService.disconnect();
return true;
case android.R.id.home:
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
private void updateConnectionState(final int resourceId) {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnectionState.setText(resourceId);
}
});
}
private void displayData(String data) {
if (data != null) {
mDataField.setText(data);
}
}
private void displayRssi(String rssi) {
if (rssi != null) {
// Log.d("-- dispaly Rssi: " + rssi);
mRssiField.setText(rssi);
}
}
private void displayRetorno(String rssi) {
if (rssi != null) {
// Log.d("-- dispaly Rssi: " + rssi);
mRssiField.setText(rssi+"Ñ");
Toast.makeText(getApplicationContext(), "SsSsSs"+"viendo", Toast.LENGTH_SHORT).show();
}
}
// Demonstrates how to iterate through the supported GATT
// Services/Characteristics.
// In this sample, we populate the data structure that is bound to the
// ExpandableListView
// on the UI.
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
private void displayGattServices(List<BluetoothGattService> gattServices) {
Log.d("displayGATTServices");
if (gattServices == null)
return;
String uuid = null;
String unknownServiceString = getResources().getString(R.string.unknown_service);
String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();
ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData = new ArrayList<ArrayList<HashMap<String, String>>>();
mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
// Loops through available GATT Services.
for (BluetoothGattService gattService : gattServices) {
HashMap<String, String> currentServiceData = new HashMap<String, String>();
uuid = gattService.getUuid().toString();
currentServiceData.put(LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));
currentServiceData.put(LIST_UUID, uuid);
gattServiceData.add(currentServiceData);
ArrayList<HashMap<String, String>> gattCharacteristicGroupData = new ArrayList<HashMap<String, String>>();
List<BluetoothGattCharacteristic> gattCharacteristics = gattService.getCharacteristics();
ArrayList<BluetoothGattCharacteristic> charas = new ArrayList<BluetoothGattCharacteristic>();
// Loops through available Characteristics.
for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
charas.add(gattCharacteristic);
HashMap<String, String> currentCharaData = new HashMap<String, String>();
uuid = gattCharacteristic.getUuid().toString();
currentCharaData.put(LIST_NAME, SampleGattAttributes.lookup(uuid, unknownCharaString));
currentCharaData.put(LIST_UUID, uuid);
gattCharacteristicGroupData.add(currentCharaData);
}
mGattCharacteristics.add(charas);
gattCharacteristicData.add(gattCharacteristicGroupData);
}
SimpleExpandableListAdapter gattServiceAdapter = new SimpleExpandableListAdapter(this, gattServiceData, android.R.layout.simple_expandable_list_item_2, new String[] { LIST_NAME, LIST_UUID },
new int[] { android.R.id.text1, android.R.id.text2 }, gattCharacteristicData, android.R.layout.simple_expandable_list_item_2, new String[] { LIST_NAME, LIST_UUID }, new int[] {
android.R.id.text1, android.R.id.text2 });
mGattServicesList.setAdapter(gattServiceAdapter);
final BluetoothGattCharacteristic characteristic = mGattCharacteristics.get(2).get(0);
final int charaProp = characteristic.getProperties();
mWriteCharacteristic = characteristic;
mBluetoothLeService.setCharacteristicNotification(mWriteCharacteristic, true);
if (mWriteCharacteristic != null) {
byte[] value = { (byte) 0x0D };
mWriteCharacteristic.setValue("ATZ");
Toast.makeText(getApplicationContext(), String.valueOf(mWriteCharacteristic.getStringValue(0)), Toast.LENGTH_SHORT).show();
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
boolean jo=mBluetoothLeService.mBluetoothGatt.readCharacteristic(mWriteCharacteristic);
Toast.makeText(getApplicationContext(), String.valueOf(mWriteCharacteristic.getStringValue(0)), Toast.LENGTH_SHORT).show();
/*mWriteCharacteristic.setValue("ATE0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATE0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATL0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATM0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATS0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATH0");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue("ATAT2");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);*/
/*mWriteCharacteristic.setValue("ATZ");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
mWriteCharacteristic.setValue(value);
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);*/
}
final BluetoothGattCharacteristic characteristic2 = mGattCharacteristics.get(0).get(0);
final int charaProp2 = characteristic2.getProperties();
mReadCharacteristic = characteristic2;
mBluetoothLeService.readCharacteristic(mReadCharacteristic);
}
private DCServiceCb mDCServiceCb = new DCServiceCb();
public class DCServiceCb implements BluetoothLeService.BLEServiceCallback {
@Override
public void displayRssi(final int rssi) {
runOnUiThread(new Runnable() {
@Override
public void run() {
DeviceControlActivity.this.displayRssi(String.valueOf(rssi));
}
});
}
@Override
public void displayRetorno (final int rssi) {
runOnUiThread(new Runnable() {
@Override
public void run() {
DeviceControlActivity.this.displayRetorno("algo!!!!");
}
});
}
@Override
public void displayData(final String data) {
runOnUiThread(new Runnable() {
@Override
public void run() {
DeviceControlActivity.this.displayData(data);
Toast.makeText(getApplicationContext(), data+"SsSsSs", Toast.LENGTH_SHORT).show();
}
});
}
@Override
public void notifyConnectedGATT() {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnected = true;
updateConnectionState(R.string.connected);
invalidateOptionsMenu();
}
});
}
@Override
public void notifyDisconnectedGATT() {
runOnUiThread(new Runnable() {
@Override
public void run() {
mConnected = false;
updateConnectionState(R.string.disconnected);
invalidateOptionsMenu();
clearUI();
}
});
}
@Override
public void displayGATTServices() {
Log.d("displayGATTServices.");
runOnUiThread(new Runnable() {
@Override
public void run() {
if (mBluetoothLeService != null) {
DeviceControlActivity.this.displayGattServices(mBluetoothLeService.getSupportedGattServices());
}
}
});
}
}
@SuppressLint("ValidFragment")
public class BleCharacterDialogFragment extends DialogFragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.write_charact_dialog, container, false);
final EditText ed = (EditText) v.findViewById(R.id.charact_value);
Button ok = (Button) v.findViewById(R.id.dialog_confirm);
Button cancel = (Button) v.findViewById(R.id.dialog_cancel);
ok.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mWriteCharacteristic != null) {
mWriteCharacteristic.setValue("AA");
mBluetoothLeService.mBluetoothGatt.writeCharacteristic(mWriteCharacteristic);
}
// characteristic.setValue("FF");
// characteristic.setValue(new byte[] {(byte) 0xFF});
// writeCharacteristicValue(characteristic);
//
Toast.makeText(getApplicationContext(), "Se envío el dato", Toast.LENGTH_SHORT).show();
dismiss();
return;
}
});
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
dismiss();
}
});
return v;
}
}
public void writeCharacteristicValue(BluetoothGattCharacteristic characteristica) {
byte[] value = { (byte) 0xFF };
characteristica.setValue(bytesToHex(value));
boolean status = mBluetoothLeService.mBluetoothGatt.writeCharacteristic(characteristica);
}
final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
public String bytesToHex(byte[] bytes) {
char[] hexChars = new char[bytes.length * 2];
int v;
for (int j = 0; j < bytes.length; j++) {
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
}
Service
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
public class BluetoothLeService extends Service {
// private final static String TAG =
// BluetoothLeService.class.getSimpleName();
private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
private String mBluetoothDeviceAddress;
BluetoothGatt mBluetoothGatt;
private int mConnectionState = STATE_DISCONNECTED;
private BLEServiceCallback mBLEServiceCb = null;
private static final int STATE_DISCONNECTED = 0;
private static final int STATE_CONNECTING = 1;
private static final int STATE_CONNECTED = 2;
private static final int GATT_SUCCESS=0;
public final static UUID UUID_HEART_RATE_MEASUREMENT = UUID.fromString(SampleGattAttributes.HEART_RATE_MEASUREMENT);
private final long READING_RSSI_TASK_FREQENCY = 500;
private static final int READ_RSSI_REPEAT = 1;
private final Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case READ_RSSI_REPEAT:
if (mBluetoothGatt != null) {
mBluetoothGatt.readRemoteRssi();
if(DeviceControlActivity.mGattCharacteristics.size()==3)
{
boolean pp=mBluetoothGatt.readCharacteristic(DeviceControlActivity.mGattCharacteristics.get(2).get(0));//
//BluetoothGattCallback.onCharacteristicRead(mBluetoothGatt, DeviceControlActivity.mGattCharacteristics.get(2).get(0), GATT_SUCCESS);
}
}
sendMessageDelayed(obtainMessage(READ_RSSI_REPEAT), READING_RSSI_TASK_FREQENCY);
break;
}
}
};
private void startReadRssi() {
if (mHandler.hasMessages(READ_RSSI_REPEAT)) {
Log.w("+++++++++ Handler already has Message: READ_RSSI_REPEAT");
}
mHandler.sendEmptyMessage(READ_RSSI_REPEAT);
}
private void stopReadRssi() {
mHandler.removeMessages(READ_RSSI_REPEAT);
}
// 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) {
Log.d("onConnectionStateChange status = " + status + ", newState = " + newState);
if (newState == BluetoothProfile.STATE_CONNECTED) {
if (mBLEServiceCb != null) {
mBLEServiceCb.notifyConnectedGATT();
}
Log.d("Connected to GATT server.");
// Attempts to discover services after successful connection.
Log.d("Attempting to start service discovery:" + mBluetoothGatt.discoverServices());
startReadRssi();
//si se conecta empiece a leer mi caracteritica
} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
if (mBLEServiceCb != null) {
mBLEServiceCb.notifyDisconnectedGATT();
}
stopReadRssi();
Log.d("Disconnected from GATT server.");
}
}
@Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.d("onServicesDiscovered status = " + status);
if (status == BluetoothGatt.GATT_SUCCESS) {
if (mBLEServiceCb != null) {
mBLEServiceCb.displayGATTServices();
}
} else {
Log.d("onServicesDiscovered received: " + status);
}
setCharacteristicNotification(DeviceControlActivity.mGattCharacteristics.get(2).get(0), true);//puede que sea mejor no ponerlo, pero no se
}
@Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
Log.d("onCharacteristicRead status: " + status);
Toast.makeText(getApplicationContext(), "MMMM"+"BBB"+"SsSsSs", Toast.LENGTH_SHORT).show();
if (status == BluetoothGatt.GATT_SUCCESS) {
displayCharacteristic(characteristic);
}
}
@Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
Log.d("------------- onCharacteristicWrite status: " + status);
// handler callback of write characteristic.
// do somethings here.
}
@Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
Log.d("onCharacteristicChanged");
Toast.makeText(getApplicationContext(), "se ejecutó el metodo de cambio en caracteristica", Toast.LENGTH_SHORT).show();
displayCharacteristic(characteristic);
}
@Override
public void onReadRemoteRssi(BluetoothGatt gatt, int rssi, int status) {
// Log.d("onReadRemoteRssi rssi = " + rssi + "; status = " +
// status);
if (mBLEServiceCb != null) {
mBLEServiceCb.displayRssi(rssi);
}
}
};
public void setBLEServiceCb(BLEServiceCallback cb) {
if (cb != null) {
mBLEServiceCb = cb;
}
}
private void displayCharacteristic(final BluetoothGattCharacteristic characteristic) {
String msg = null;
// 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("Heart rate format UINT16.");
} else {
format = BluetoothGattCharacteristic.FORMAT_UINT8;
Log.d("Heart rate format UINT8.");
}
final int heartRate = characteristic.getIntValue(format, 1);
Log.d(String.format("Received heart rate: %d", heartRate));
msg = 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));
msg = new String(data) + "\n" + stringBuilder.toString();
}
}
if (mBLEServiceCb != null) {
mBLEServiceCb.displayData(msg);
}
}
public class LocalBinder extends Binder {
BluetoothLeService getService() {
return BluetoothLeService.this;
}
}
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}
@Override
public boolean onUnbind(Intent intent) {
close();
return super.onUnbind(intent);
}
private final IBinder mBinder = new LocalBinder();
public boolean initialize() {
// For API level 18 and above, get a reference to BluetoothAdapter
// through
// BluetoothManager.
if (mBluetoothManager == null) {
mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (mBluetoothManager == null) {
Log.e("Unable to initialize BluetoothManager.");
return false;
}
}
mBluetoothAdapter = mBluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
Log.e("Unable to obtain a BluetoothAdapter.");
return false;
}
return true;
}
public boolean connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
Log.w("BluetoothAdapter not initialized or unspecified address.");
return false;
}
// Previously connected device. Try to reconnect.
if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress) && mBluetoothGatt != null) {
Log.d("Trying to use an existing mBluetoothGatt for connection.");
if (mBluetoothGatt.connect()) {
mConnectionState = STATE_CONNECTING;
return true;
} else {
return false;
}
}
final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
Log.w("Device not found. Unable to connect.");
return false;
}
// We want to directly connect to the device, so we are setting the
// autoConnect
// parameter to false.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
Log.d("Trying to create a new connection.");
mBluetoothDeviceAddress = address;
mConnectionState = STATE_CONNECTING;
return true;
}
public void disconnect() {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w("BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.disconnect();
}
public void close() {
if (mBluetoothGatt == null) {
return;
}
mBluetoothGatt.close();
mBluetoothGatt = null;
}
/**
* Request a read on a given {@code BluetoothGattCharacteristic}. The read
* result is reported asynchronously through the
* {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
* callback.
*
* @param characteristic
* The characteristic to read from.
*/
public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
Toast.makeText(getApplicationContext(), "readCharacteristic en Servicio", Toast.LENGTH_SHORT).show();
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w("BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.readCharacteristic(characteristic);
}
/**
* Requst a write on a give {@code BluetoothGattCharacteristic}. The write
* result is reported asynchronously through the
* {@code BluetoothGattCallback#onCharacteristicWrite(andorid.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
* callback.
*/
public void writeCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w("BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.writeCharacteristic(characteristic);
}
/**
* Enables or disables notification on a give characteristic.
*
* @param characteristic
* Characteristic to act on.
* @param enabled
* If true, enable notification. False otherwise.
*/
public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic, boolean enabled) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
Log.w("BluetoothAdapter not initialized");
return;
}
mBluetoothGatt.setCharacteristicNotification(characteristic, true);
// This is specific to Heart Rate Measurement.
if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);
}
}
/**
* Retrieves a list of supported GATT services on the connected device. This
* should be invoked only after {@code BluetoothGatt#discoverServices()}
* completes successfully.
*
* @return A {@code List} of supported services.
*/
public List<BluetoothGattService> getSupportedGattServices() {
if (mBluetoothGatt == null)
return null;
return mBluetoothGatt.getServices();
}
public interface BLEServiceCallback {
public void displayRssi(int rssi);
public void displayData(String data);
public void notifyConnectedGATT();
public void notifyDisconnectedGATT();
public void displayGATTServices();
public void displayRetorno(int rssi);
}
}
Answer
To receive notification in Android you need to set characteristic notification to true
gatt.setCharacteristicNotification(characteristic, true);
You also need to set the client characteristic configuration descriptor 0x2902
// 0x2902 org.bluetooth.descriptor.gatt.client_characteristic_configuration.xml
UUID uuid = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(uuid);
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
gatt.writeDescriptor(descriptor);
A better API would be for setCharacteristicNotification to set the descriptor, but unfortunately it doesn't seem to work that way.