Develop Reference

BLE(Bluetooth Low Energy)

I try to implement Connection between two devices(Any ios/Android) and transfer text using BLE
I try too many demos from GitHub and also try from documentation step by step but I am not getting a success
some time give Error like :
> GATT server 133
or
>android.bluetooth.BluetoothGattCharacteristic android.bluetooth.BluetoothGattService.getCharacteristic(java.util.UUID)' on a null object reference
Please help me
Thank you so much
Here is the my two activity code one ble class and one activity to call function from BLE claass
I want just pass small text to android to android or android to ios using ble
please help I tried from too many days
================================================================
public class MainActivity extends AppCompatActivity {
ArrayList<String> getDevicess;
List<BluetoothDevice> getConnectedDevicess;
TextView tvscan;
TextView tvConnected;
TextView tvsend;
Ble ble;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvsend = (TextView) findViewById(R.id.tvsend);
getDevicess = new ArrayList<>();
getConnectedDevicess = new ArrayList<>();
ble = new Ble(this, getApplicationContext(), "zad");
ble.enableBle();
ble.checkPermission(0);
ble.scanLeDevice(true, 1000);
//after scan and connect click on send button then give error
tvsend.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
ble.writeCharacteristics(hexStringToByteArray("abcdefg"), UUID.fromString("fffffff0-00f7-4000-b000-000000000000"), UUID.fromString("fffffff5-00f7-4000-b000-000000000000"));
}
});
}
public byte[] hexStringToByteArray(String s) {
int len = s.length()-1;
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
}
return data;
}
}
===========================================BLE CLass==================
// Function To Write Characteristics .. !
#TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
public void writeCharacteristics(byte[] data, UUID DLE_SERVICE, UUID DLE_WRITE_CHAR) {
BluetoothGattService Service = mBluetoothGatt.getService(DLE_SERVICE);
if (Service == null) {
Log.d(TAG, "service not found!");
//return false;
}
BluetoothGattCharacteristic charc1 = Service.getCharacteristic(DLE_WRITE_CHAR);
if (charc1 == null) {
Log.d(TAG, "char not found!");
Log.d(TAG, "CHARAC_-TRST" + charc1.getUuid());
// return false;
}
// charc1.setValue(new byte[]{0x00, 0x05, 0x10, 0x01, 0x3E, 0x01, 0x23});
charc1.setValue(data);
boolean stat = mBluetoothGatt.writeCharacteristic(charc1);
Log.d(TAG, "FINISHED WRITTING CHAR 1 status write :(status)" + stat);
if (data != null && data.length > 0) {
final StringBuilder stringBuilder = new StringBuilder(data.length);
for (byte byteChar : data)
stringBuilder.append(String.format("%02X ", byteChar));
}
}

This snippet is problematic:
public void displayBleService(List<BluetoothGattService> gattServices) {
Log.d(TAG, "display Services");
List<BluetoothGattCharacteristic> characteristics = new ArrayList<BluetoothGattCharacteristic>();
for (BluetoothGattService services : gattServices) {
Log.d(TAG, "SERVICES == ." + services.getUuid());
characteristics = services.getCharacteristics();
for (BluetoothGattCharacteristic characteristic : characteristics) {
Log.d(TAG, "CAHRACTERISTICS == ." + characteristic.getUuid() + "--" + characteristic.getProperties());
//enableNotification(characteristic, true);
}
}
}
the services is null, and thus the services.getCharacteristics() is provoking the NPE.
Please debug your code, and make sure you have BLUETOOTH_ADMIN permission as well. Feel free to add necessary null-guards as well at your own discretion.

SeekBar value sent via Bluetooth crashes the app

When trying to control a servo motor connected to an Arduino board using the progress of a SeekBar, my app crashes. I will post the code below maybe someone can catch the thing that I am missing.
I mention that i am using a BluetoothHelper which can be found at this address : https://github.com/BasicAirData/BluetoothHelper
Android code:
public class CarConnection {
BluetoothManager mBluetoothManager;
BluetoothHelper mBluetoothHelper;
MainActivity mMainActivity;
public CarConnection(MainActivity mainActivity) {
mMainActivity = mainActivity;
mBluetoothHelper = new BluetoothHelper();
mBluetoothHelper.setBluetoothHelperListener(new BluetoothHelper.BluetoothHelperListener() {
#Override
public void onBluetoothHelperMessageReceived(BluetoothHelper bluetoothhelper, final String message) {
Toast.makeText(mMainActivity, "Message received: " + message, Toast.LENGTH_SHORT).show();
}
#Override
public void onBluetoothHelperConnectionStateChanged(BluetoothHelper bluetoothhelper, boolean isConnected) {
// Do something, depending on the new connection status
String connectedStatus = isConnected ? "connected" : "disconnected";
Toast.makeText(mMainActivity, "Connection status changed: " + connectedStatus, Toast.LENGTH_SHORT).show();
}
mBluetoothHelper.Connect("VOLAN BT");
}
public void setAngle(int angle) {
mBluetoothHelper.SendMessage(Integer.toString(angle));
Toast.makeText(mMainActivity, "Sent value: " + Integer.toString(angle), Toast.LENGTH_LONG).show();
}
And main activity class:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
start = (Button) findViewById(R.id.start_sending);
angleValue = (SeekBar) findViewById(R.id.simple_sb);
valueSent = (TextView) findViewById(R.id.value_sent);
final MainActivity mainActivityInstance = this;
start.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
CarConnection mCarConnection = new CarConnection(mainActivityInstance);
}
});
angleValue.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
#Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
valueSent.setText("Value sent is: " + Integer.toString(progress));
mCarConnection.setAngle(progress);
}
#Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
#Override
public void onStopTrackingTouch(SeekBar seekBar) {
mCarConnection.setAngle(seekBar.getProgress());
}
});
}
Arduino code:
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>
#include <SoftwareSerial.h> // TX RX software library for bluetooth
#include <Servo.h> // servo library
Servo myservo; // servo name
#define outputA 28
#define outputB 30
LiquidCrystal_I2C lcd(0x3F, 2, 1, 0, 4, 5, 6, 7);
int angle = 0;
int aState;
int aLastState;
int bluetoothTx = 10; // bluetooth tx to 10 pin
int bluetoothRx = 11; // bluetooth rx to 11 pin
SoftwareSerial bluetooth(bluetoothTx, bluetoothRx);
void setup()
{
// initialize the lcd
lcd.setBacklightPin(3, POSITIVE);
lcd.setBacklight(HIGH); //
lcd.begin(16, 2);
lcd.clear();
pinMode(12, OUTPUT);
digitalWrite(12, HIGH);
pinMode(23, OUTPUT);
digitalWrite(23, LOW);
pinMode (outputA, INPUT);
pinMode (outputB, INPUT);
myservo.attach(7); // attach servo signal wire to pin 6
//Setup usb serial connection to computer
Serial.begin(9600);
//Setup Bluetooth serial connection to android
bluetooth.begin(9600);
aLastState = digitalRead(outputA);
}
void loop()
{
//Read from bluetooth and write to usb serial
if(bluetooth.available()> 0 ) // receive number from bluetooth
{
int servopos = bluetooth.read(); // save the received number to servopos
Serial.println(servopos); // serial print servopos current number received from bluetooth
myservo.write(servopos); // roate the servo the angle received from the android app
}
aState = digitalRead(outputA);
if (aState != aLastState) {
if (digitalRead(outputB) != aState) {
angle ++;
}
else {
angle --;
}
float angle_1 = angle * (1023.0 / 360);
float angle2 = angle_1 / (2.84 );
Serial.print("Position: ");
Serial.println(angle2);
lcd.clear();
lcd.print("Position: ");
lcd.print(int(angle2));
lcd.print("");
lcd.setCursor(0, 1);
}
aLastState = aState;
}
When pressing "start" button, the phone responses with the message "Connected"!
Thank you in advance!

I think the problem is that onBluetoothHelperConnectionStateChanged() is not called in the UI thread (in order to not alter the UI performances), thus you cannot call Toast.makeText() here.
A possible solution is to implement the listener in your class CarConnection this way:
public void onBluetoothHelperMessageReceived(BluetoothHelper bluetoothhelper, final String message) {
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(mMainActivity, "Message received: " + message, Toast.LENGTH_SHORT).show();
}
});
}

Android BLE Gatt connection change statuses

I have an android app to connect to a BLE device and write to it. I can successfully connect, read and write to it. As a part of testing, we are trying different disconnection scenarios.
Sometimes, if BLE device disconnects the connection, I get the connection change as disconnect with status value as 19. Also if there is any bond error, status equals 22. If I programmatically disconnect the connection, this status gives me 0. But none of these states except 0 are specified in android documentation.
Posting a sample BluetoothGattCallback
private BluetoothGattCallback bluetoothGattCallback = new BluetoothGattCallback() {
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
Log.i(TAG, "onConnectionStateChange status: "+status+", newState: "+newState);
/*i need to know the possible values for this status variable*/
if(newState == BluetoothProfile.STATE_CONNECTED) {
gatt.discoverServices();
} else {
gatt.close();
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
Log.i(TAG, "onServicesDiscovered service discovered");
}
};
Does anyone face this same problem and sorted out the list of statuses. I need to know the possible values for status variable in onConnectionStateChange method

Here is the list of codes i have
Programmatically disconnected - 0
Device went out of range - 8
Disconnected by device - 19
Issue with bond - 22
Device not found - 133(some phone it gives 62)
I have tested disconnect scenario's in 5.0.2, 5.1, 6.0 and 6.0.1. But only found this bond issue code in 6.0.1 android version.

Sorry to bring up an old question, but here is the solution for many of the problems i've had with Bluetooth (BLE) 4.0. Sorry again for the big classes below but be sure they are needed and no method there is irrelevant or unused.
public abstract class AbstractBluetoothBroadcaster extends BroadcastReceiver {
protected static final String LOG_TAG = BluetoothLowEnergy.LOG_TAG;
protected BluetoothLowEnergy bluetoothLowEnergy;
public AbstractBluetoothBroadcaster(BluetoothLowEnergy bluetoothLowEnergy, String action){
super();
this.bluetoothLowEnergy = bluetoothLowEnergy;
IntentFilter intentFilterStateChange = new IntentFilter(action);
intentFilterStateChange.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
this.bluetoothLowEnergy.getActivity().registerReceiver(this, intentFilterStateChange);
}
public void onDestroy(){
this.bluetoothLowEnergy.getActivity().unregisterReceiver(this);
}
}
public class BluetoothBondStateBroadcaster extends AbstractBluetoothBroadcaster {
private BluetoothLowEnergy bluetoothLowEnergy;
private boolean deviceBonded;
public BluetoothBondStateBroadcaster(BluetoothLowEnergy bluetoothLowEnergy) {
super(bluetoothLowEnergy, BluetoothDevice.ACTION_BOND_STATE_CHANGED);
this.bluetoothLowEnergy = bluetoothLowEnergy;
this.deviceBonded = false;
}
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action == null){
return;
}
BluetoothDevice bluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (action.equals(BluetoothDevice.ACTION_BOND_STATE_CHANGED) &&
bluetoothDevice != null &&
bluetoothDevice.getAddress().equals(bluetoothLowEnergy.getDeviceUUID())) {
int state = intent.getIntExtra(BluetoothDevice.EXTRA_BOND_STATE, -1);
switch (state) {
case BluetoothDevice.BOND_NONE:
Log.d(LOG_TAG, " NOT BONDED - dev " + bluetoothDevice.getAddress());
this.deviceBonded = false;
break;
case BluetoothDevice.BOND_BONDING:
Log.d(LOG_TAG, " BONDING ... - dev " + bluetoothDevice.getAddress());
break;
case BluetoothDevice.BOND_BONDED:
Log.d(LOG_TAG, " BONDED - dev " + bluetoothDevice.getAddress());
deviceBonded = true;
bluetoothLowEnergy.onBluetoothBonded();
break;
default:
break;
}
}
}
public void resetDeviceBonded(){
this.deviceBonded = false;
}
public boolean isDeviceBonded() {
return deviceBonded;
}
}
public class BluetoothPairingBroadcaster extends AbstractBluetoothBroadcaster {
private String devicePIN;
public BluetoothPairingBroadcaster(BluetoothLowEnergy bluetoothLowEnergy){
super(bluetoothLowEnergy, BluetoothDevice.ACTION_PAIRING_REQUEST);
this.devicePIN = "";
}
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (action == null){
return;
}
BluetoothDevice bluetoothDevice = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
int pairingType = intent.getIntExtra(BluetoothDevice.EXTRA_PAIRING_VARIANT, BluetoothDevice.ERROR);
if (action.equals(BluetoothDevice.ACTION_PAIRING_REQUEST) &&
bluetoothDevice != null &&
bluetoothDevice.getAddress().equals(bluetoothLowEnergy.getDeviceUUID()) &&
!getDevicePIN().isEmpty()) {
if (pairingType == BluetoothDevice.PAIRING_VARIANT_PIN){
bluetoothDevice.setPin(getDevicePIN().getBytes());
Log.d(LOG_TAG," Auto-entering pin - " + getDevicePIN());
bluetoothDevice.createBond();
Log.d(LOG_TAG," pin entered and request sent...");
abortBroadcast();
}
}
}
public void setDevicePIN(String pin){
this.devicePIN = pin;
}
public String getDevicePIN(){
return this.devicePIN ;
}
}
public class BluetoothLowEnergy extends BluetoothGattCallback {
// listener that has the methods that the application (activity)
// will use to send / receive data, or to reflect the system state
// in the UI
public interface BluetoothListener {
/**
* Triggered when the scanning has started successfully
*/
void onBluetoothStartScan();
/**
* Triggered when the scanning stops
* #param scanResults results of the scanning
*/
void onBluetoothStopScan(Collection<BluetoothDevice> scanResults);
/**
* Triggered when the device is ready to send/receive data
*/
void onBluetoothConnectionReady();
/**
* Triggered when a bluetooth msg is received
* #param msg message received
*/
void onBluetoothReceiveMsg(String msg);
/**
* Triggered whenever data is send
* #param success true means data was sent fine to the remote device, false otherwise
*/
void onBluetoothSend(String data, boolean success);
/**
* Triggered if no bluetooth is connected, and we need a connection
* to send / receive / discover services
*/
void onBluetoothNotConnected();
}
// custom exceptions
public class BluetoothNotEnabledException extends Exception { }
public class BluetoothLowEnergyNotSupported extends Exception { }
public class BluetoothDeviceNotFound extends Exception { }
// service and characteristic uuids that are going to be used to
// send / receive data between central and peripheral GATTs
private static final String SERVICE_UUID = "FFE0-";
private static final String CHARACTERISTIC_UUID = "FFE1-";
// timeout for bluetooth scan (in ms)
public static final int SCAN_TIMEOUT = 5000;
// BLE LOG TAG
public static final String LOG_TAG = "BLUETOOTH_BLE";
// model
private boolean bluetoothScanning;
private boolean bluetoothConnected;
private Map<String, BluetoothDevice> bluetoothScanResults;
// gui
private Activity activity;
// bluetooth
private BluetoothAdapter bluetoothAdapter;
private BluetoothLeScanner bluetoothLeScanner;
private ScanCallback bluetoothScanCallback;
private BluetoothGatt bluetoothGatt;
private BluetoothGattCharacteristic characteristic;
public BluetoothLowEnergy(Activity activity, BluetoothListener bluetoothListener){
this.activity = activity;
this.bluetoothListener = bluetoothListener;
// this keeps track of the scanning and connection states
this.bluetoothScanning = this.bluetoothConnected = false;
// keeps track of the scanning results
this.bluetoothScanResults = new HashMap<>();
// set bluetooth pairing request and bonded callback
// these broadcasters will be responsible to detect and validate
// the bonded state of your device
this.pairingRequestBroadcaster = new BluetoothPairingBroadcaster(this);
this.bondedBroadcaster = new BluetoothBondStateBroadcaster(this);
// set the scan callback methods that will add results to
// this.bluetoothScanResults map
this.bluetoothScanCallback = new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);
addScanResult(result);
}
#Override
public void onBatchScanResults(List<ScanResult> results) {
super.onBatchScanResults(results);
for (ScanResult result: results) {
addScanResult(result);
}
}
#Override
public void onScanFailed(int errorCode) {
super.onScanFailed(errorCode);
Log.e(LOG_TAG, "Scan Failed with code " + errorCode);
}
private void addScanResult(ScanResult result) {
BluetoothDevice device = result.getDevice();
String deviceAddress = device.getAddress();
bluetoothScanResults.put(deviceAddress, device);
Log.d(LOG_TAG, "Found device " + deviceAddress);
}
};
// Use this to determine whether BLE is supported on the device.
if (!this.activity.getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
throw new BluetoothLowEnergyNotSupported();
}
}
/**
* This method should be called when the activity is destroyed
*/
public void onDestroy(){
this.bondedBroadcaster.onDestroy();
this.pairingRequestBroadcaster.onDestroy();
this.disconnect();
}
/**
* This method is called when we finish pairing/bonding to the device
*/
public void onBluetoothBonded(){
// if we have the services already discovered, then we can
// send/receive data, to do so we call the bluetooth listener below
if (servicesDiscovered){
this.bluetoothListener.onBluetoothConnectionReady();
// if we know we have a connection established, then we can
// discover services
} else if (bluetoothConnected){
bluetoothGatt.discoverServices();
}
}
/**
* This method is called whenever a connection is established or a disconnection happens
*/
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
BluetoothDevice bluetoothDevice = gatt.getDevice();
// if these conditions == true, then we have a disconnect
if ( status == BluetoothGatt.GATT_FAILURE ||
status != BluetoothGatt.GATT_SUCCESS ||
newState == BluetoothProfile.STATE_DISCONNECTED) {
Log.d(LOG_TAG, String.format(Locale.getDefault(),
"Disconnected from %s (%s) - status %d - state %d",
bluetoothDevice.getName(),
bluetoothDevice.getAddress(),
status,
newState
));
this.disconnect();
// if these conditions == true, then we have a successful connection
} else if (newState == BluetoothProfile.STATE_CONNECTED) {
bluetoothConnected = true;
Log.d(LOG_TAG, String.format(Locale.getDefault(),
"Connected to %s (%s) - status %d - state %d",
bluetoothDevice.getName(),
bluetoothDevice.getAddress(),
status,
newState
));
// this sleep is here to avoid TONS of problems in BLE, that occur whenever we start
// service discovery immediately after the connection is established
try {
Thread.sleep(600);
} catch (InterruptedException e) {
e.printStackTrace();
}
gatt.discoverServices();
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
if (status != BluetoothGatt.GATT_SUCCESS) {
return;
}
// BEGIN - find the service and characteristic that we want (defined as a static attribute
// of the BluetoothLowEnergy class)
Log.d(LOG_TAG, "Discovering services ...");
BluetoothGattService service = null;
for (BluetoothGattService serv: gatt.getServices()){
Log.d(LOG_TAG, "Found service " + serv.getUuid().toString());
if (serv.getUuid().toString().toUpperCase().contains(SERVICE_UUID)){
service = serv;
Log.d(LOG_TAG, "---> Selected service " + serv.getUuid().toString());
break;
}
}
if (service == null){
return;
}
for (BluetoothGattCharacteristic charac: service.getCharacteristics()){
Log.d(LOG_TAG, "Found characteristic " + charac.getUuid().toString());
if (charac.getUuid().toString().toUpperCase().contains(CHARACTERISTIC_UUID)){
this.characteristic = charac;
Log.d(LOG_TAG, "---> Selected characteristic " + charac.getUuid().toString());
break;
}
}
if (this.characteristic == null){
return;
}
Log.d(LOG_TAG, "Setting write and notification to the characteristic ...");
bluetoothAdapter.cancelDiscovery();
// END - find the service and characteristic
// set that we want to write to the selected characteristic and be notified if
// it changes (the remote GATT peripheral sends data to the Android's GATT Center)
this.characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
gatt.setCharacteristicNotification(this.characteristic, true);
// we finished service discovery
this.servicesDiscovered = true;
// if we have paired/bonded then we are ready to send/receive data
if (pairingRequestBroadcaster.getDevicePIN().isEmpty() || bondedBroadcaster.isDeviceBonded()) {
this.bluetoothListener.onBluetoothConnectionReady();
}
}
#Override
public void onCharacteristicRead(BluetoothGatt gatt, BluetoothGattCharacteristic charac, int status) {
super.onCharacteristicRead(gatt, charac, status);
restartDisconnectTimeout();
if (status != BluetoothGatt.GATT_SUCCESS) {
return;
}
try {
String characValue = new String(charac.getValue(), CHARSET)
.replaceAll(DATA_FILTER_REGEX,"");
Log.i(LOG_TAG, String.format(Locale.getDefault(),
"Characteristic Read - %s",
characValue
));
if (charac.getUuid().equals(this.characteristic.getUuid())) {
this.bluetoothListener.onBluetoothReceiveMsg(characValue);
}
} catch (UnsupportedEncodingException e) {
Log.e(LOG_TAG, "Characteristic Read - Failed to convert message string to byte array");
}
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic charac, int status) {
super.onCharacteristicWrite(gatt, charac, status);
restartDisconnectTimeout();
try {
String characValue = new String(charac.getValue(), CHARSET);
Log.i(LOG_TAG, String.format(Locale.getDefault(),
"Characteristic Write - SUCCESS - %s",
characValue
));
bluetoothListener.onBluetoothSend( characValue, (status == BluetoothGatt.GATT_SUCCESS) );
} catch (UnsupportedEncodingException e) {
Log.e(LOG_TAG, "Characteristic Write - Failed to convert message string to byte array");
}
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic charac) {
super.onCharacteristicChanged(gatt, charac);
Log.d(LOG_TAG,"Characteristic Changed");
onCharacteristicRead(gatt, charac, BluetoothGatt.GATT_SUCCESS);
}
/**
* Remove pairing/bonding of the device
* #param device Device to remove bonding
*/
public static void removeBond(BluetoothDevice device){
try {
if (device == null){
throw new Exception();
}
Method method = device.getClass().getMethod("removeBond", (Class[]) null);
method.invoke(device, (Object[]) null);
Log.d(LOG_TAG, "removeBond() called");
Thread.sleep(600);
Log.d(LOG_TAG, "removeBond() - finished method");
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* Clears the GATT services cache, so that new services can be discovered
* #param bluetoothGatt GATT Client to clear service's discovery cache
*/
public static void refresh(BluetoothGatt bluetoothGatt){
try {
Method method = bluetoothGatt.getClass().getMethod("refresh", (Class[]) null);
method.invoke(bluetoothGatt, (Object[]) null);
} catch (Exception e){
e.printStackTrace();
}
}
/**
* Connect to the GATT Peripheral device
* #param uuid GATT Peripheral address / mac / uuid to connect to
* #param pin PIN to authenticate and pair to the device
*/
public void connect(String uuid, String pin) throws BluetoothNotEnabledException, BluetoothDeviceNotFound {
checkBluetooth();
// do not connect twice
if (this.isConnected()){
return;
}
// get device
BluetoothDevice device = this.bluetoothScanResults.get(uuid);
if (device == null){
throw new BluetoothDeviceNotFound();
}
this.deviceUUID = uuid;
pairingRequestBroadcaster.setDevicePIN(pin);
removeBond(device);
// create connection to the bluetooth device
bluetoothGatt = device.connectGatt(activity, false, this);
refresh(bluetoothGatt);
}
/**
* Disconnect from BLE device. This method should be called whenever we want to
* close the APP, or the BLE connection.
*/
public void disconnect() {
Log.d(LOG_TAG, "disconnect() - executed");
if (bluetoothGatt != null) {
if (characteristic != null) {
bluetoothGatt.setCharacteristicNotification(characteristic, false);
}
//remove device authorization/ bond/ pairing
removeBond(bluetoothGatt);
// disconnect now
bluetoothGatt.disconnect();
bluetoothGatt.close();
Log.d(LOG_TAG, "disconnect() - bluetoothGatt disconnect happened");
}
bluetoothGatt = null;
characteristic = null;
bluetoothConnected = false;
servicesDiscovered = false;
// set device as not bonded anymore
bondedBroadcaster.resetDeviceBonded();
}
/**
* bluetooth nearby devices scan is on
* #return true if scanning is on, false otherwise
*/
public boolean isScanning(){
return (this.bluetoothScanning);
}
/**
* Check bluetooth system state (on or off)
* #return true if system is on, false otherwise
*/
public boolean isEnabled(){
try {
checkBluetooth();
return bluetoothAdapter.isEnabled();
} catch (BluetoothNotEnabledException e) {
return false;
}
}
/**
* Check bluetooth connection
* #return true if connected, false otherwise
*/
public boolean isConnected(){
return (this.bluetoothConnected);
}
/**
* Start bluetooth scan for nearby devices
* #param filters Scan filters that define what devices to scan for
*/
public void startScan(List<ScanFilter> filters)
throws BluetoothNotEnabledException{
checkBluetooth();
// dont run two scans simultaneously
if (isScanning()) {
return;
}
// disconnect previously connected devices
if (isConnected()) {
this.disconnect();
return;
}
// setup bluetooth scanning settings
ScanSettings settings = new ScanSettings.Builder()
.setScanMode(ScanSettings.SCAN_MODE_LOW_POWER)
.build();
// start scanning
this.bluetoothScanning = true;
this.bluetoothScanResults.clear();
this.bluetoothLeScanner = bluetoothAdapter.getBluetoothLeScanner();
// Stops scanning after a pre-defined scan period.
Handler bluetoothHandler = new Handler();
bluetoothHandler.postDelayed(new Runnable() {
#Override
public void run() {
stopScan();
}
}, SCAN_TIMEOUT);
// start scan with default scan callback
this.bluetoothLeScanner.startScan(filters, settings, bluetoothScanCallback);
// we have started successfully the BLE scanning
bluetoothListener.onBluetoothStartScan();
}
/**
* Stop bluetooth scan for nearby devices
*/
public void stopScan(){
if (!bluetoothScanning) {
return;
}
// set app scan state to false
bluetoothScanning = false;
if (bluetoothLeScanner != null) {
bluetoothLeScanner.stopScan(bluetoothScanCallback);
bluetoothLeScanner = null;
}
// we have stopped BLE scanning, call the user's callback
bluetoothListener.onBluetoothStopScan(bluetoothScanResults.values());
}
/**
* Send a message via bluetooth
* #param msg message to send
*/
public void send(String msg) {
if (!bluetoothConnected || characteristic == null){
bluetoothListener.onBluetoothNotConnected();
return;
}
try {
msg = msg.replaceAll(DATA_FILTER_REGEX, "") + TERMINATION_CHAR;
Log.d(LOG_TAG, String.format(Locale.getDefault(),
"Sending message: %s",
msg));
characteristic.setValue(msg.getBytes(CHARSET));
bluetoothGatt.writeCharacteristic(characteristic);
} catch (UnsupportedEncodingException e) {
Log.e(LOG_TAG,
"BluetoothLowEnergy.send: Failed to convert message string to byte array");
}
}
public String getDeviceUUID(){
return deviceUUID;
}
public Activity getActivity(){
return activity;
}
/**
* Check if bluetooth is enabled and working properly
*/
private void checkBluetooth() throws BluetoothNotEnabledException{
if (bluetoothAdapter == null) {
final BluetoothManager bluetoothManager =
(BluetoothManager) activity.getSystemService(Context.BLUETOOTH_SERVICE);
if (bluetoothManager == null){
throw new BluetoothNotEnabledException();
}
bluetoothAdapter = bluetoothManager.getAdapter();
}
// Ensures Bluetooth is available on the device and it is enabled. If not,
// displays a dialog requesting user permission to enable Bluetooth.
if (bluetoothAdapter == null || !bluetoothAdapter.isEnabled()) {
throw new BluetoothNotEnabledException();
}
}
}
The key methods and functions to avoid problems used above are:
Thread.sleep(600)
removeBond(device)
refresh(gatt)
gatt.disconnect()
gatt.close()

In my case I got this response from bluetooth stack because the device was already bonded with my phone. I removed it from my settings and the error 22 vanished.

in aosp (android source code). you can find any error in bluetooth source code, and know the meaning of status code.
the file path is system/bt/stack/include/gatt_api.h
Here's the link: https://android.googlesource.com/platform/system/bt/+/ea7ab70a711e642653dd5922b83aa04a53af9e0e/stack/include/gatt_api.h but it all display by hex.
for example:
hex
Decimal
reason
0x08
8
connection timeout
0x13
19
connection terminate by peer user
0x16
22
connectionterminated by local host
0x22
34
connection fail for LMP response tout
0x85
133
gatt_error

Android BluetoothGatt becomes null on activity change

I am developing an android application which requires me to send data to a Bluetooth Low Energy device.After the connection event is successful and after I receive a call back message I want to change the activity and display new GUI where on switch click I want to send data to connected device. The problem is after the activity has changed my BluetoothGatt becomes null and BluetoothGattCharacteristic also becomes null and i am not able to send the data. how can I solve this issue? Below is my code main class which onResume calls the connection activity and connects to first available device and after connection is successful it receives callback message and changes the activity.
public class MainActivity extends Activity implements BluetoothLeUart.Callback {
public TextView messages;
private BluetoothLeUart uart;
public void writeLine(final CharSequence text) {
runOnUiThread(new Runnable() {
#Override
public void run() {
messages.append(text);
messages.append("\n");
}
});
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
messages = (TextView) findViewById(R.id.messages);
// Initialize UART.
uart = new BluetoothLeUart(getApplicationContext());
messages.setMovementMethod(new ScrollingMovementMethod());
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
protected void onResume() {
super.onResume();
writeLine("Scanning for devices ...");
uart.registerCallback(this);
uart.connectFirstAvailable();
}
#Override
protected void onStop() {
super.onStop();
uart.unregisterCallback(this);
uart.disconnect();
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
// UART Callback event handlers.
// UART Callback event handlers.
#Override
public void onConnected(BluetoothLeUart uart) {
// Called when UART device is connected and ready to send/receive data.
//messages.append("connected2");
writeLine("Connected!");
Intent intent = new Intent(MainActivity.this,SwitchClass.class);
startActivity(intent);
}
}
This is my codes BluetoothLeUart class which does connection activity and gives callback message.
public class BluetoothLeUart extends BluetoothGattCallback implements BluetoothAdapter.LeScanCallback {
// UUIDs for UART service and associated characteristics.
public static UUID UART_UUID = UUID.fromString("6E400001-B5A3-F393-E0A9-E50E24DCCA9E");
public static UUID TX_UUID = UUID.fromString("6E400002-B5A3-F393-E0A9-E50E24DCCA9E");
public static UUID RX_UUID = UUID.fromString("6E400003-B5A3-F393-E0A9-E50E24DCCA9E");
// UUID for the UART BTLE client characteristic which is necessary for notifications.
public static UUID CLIENT_UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
// UUIDs for the Device Information service and associated characeristics.
public static UUID DIS_UUID = UUID.fromString("0000180a-0000-1000-8000-00805f9b34fb");
public static UUID DIS_MANUF_UUID = UUID.fromString("00002a29-0000-1000-8000-00805f9b34fb");
public static UUID DIS_MODEL_UUID = UUID.fromString("00002a24-0000-1000-8000-00805f9b34fb");
public static UUID DIS_HWREV_UUID = UUID.fromString("00002a26-0000-1000-8000-00805f9b34fb");
public static UUID DIS_SWREV_UUID = UUID.fromString("00002a28-0000-1000-8000-00805f9b34fb");
// Internal UART state.
private Context context;
private WeakHashMap<Callback, Object> callbacks;
private BluetoothAdapter adapter;
private BluetoothGatt gatt;
private BluetoothGattCharacteristic tx;
private BluetoothGattCharacteristic rx;
private boolean connectFirst;
private boolean writeInProgress; // Flag to indicate a write is currently in progress
// Queues for characteristic read (synchronous)
private Queue<BluetoothGattCharacteristic> readQueue;
// Interface for a BluetoothLeUart client to be notified of UART actions.
public interface Callback {
public void onConnected(BluetoothLeUart uart);
public void onConnectFailed(BluetoothLeUart uart);
public void onDisconnected(BluetoothLeUart uart);
public void onReceive(BluetoothLeUart uart, BluetoothGattCharacteristic rx);
public void onDeviceFound(BluetoothDevice device);
public void onDeviceInfoAvailable();
}
public BluetoothLeUart(Context context) {
super();
this.context = context;
this.callbacks = new WeakHashMap<Callback, Object>();
this.adapter = BluetoothAdapter.getDefaultAdapter();
this.gatt = null;
this.tx = null;
this.rx = null;
this.disManuf = null;
this.disModel = null;
this.disHWRev = null;
this.disSWRev = null;
this.disAvailable = false;
this.connectFirst = false;
this.writeInProgress = false;
this.readQueue = new ConcurrentLinkedQueue<BluetoothGattCharacteristic>();
}
// Send data to connected UART device.
public void sendbyte(byte[] data) {
if (tx == null || data == null || data.length == 0) {
// Do nothing if there is no connection or message to send.
return;
}
// Update TX characteristic value. Note the setValue overload that takes a byte array must be used.
tx.setValue(data);
writeInProgress = true; // Set the write in progress flag
gatt.writeCharacteristic(tx);
// ToDo: Update to include a timeout in case this goes into the weeds
while (writeInProgress); // Wait for the flag to clear in onCharacteristicWrite
gatt.readCharacteristic(rx);
}
// Send data to connected UART device.
public void send(String data) {
if (data != null && !data.isEmpty()) {
sendbyte(data.getBytes(Charset.forName("UTF-8")));
}
}
// Register the specified callback to receive UART callbacks.
public void registerCallback(Callback callback) {
callbacks.put(callback, null);
}
// Unregister the specified callback.
public void unregisterCallback(Callback callback) {
callbacks.remove(callback);
}
// Disconnect to a device if currently connected.
public void disconnect() {
if (gatt != null) {
gatt.disconnect();
}
gatt = null;
tx = null;
rx = null;
}
// Stop any in progress UART device scan.
public void stopScan() {
if (adapter != null) {
adapter.stopLeScan(this);
}
}
// Start scanning for BLE UART devices. Registered callback's onDeviceFound method will be called
// when devices are found during scanning.
public void startScan() {
if (adapter != null) {
adapter.startLeScan(this);
}
}
// Connect to the first available UART device.
public void connectFirstAvailable() {
// Disconnect to any connected device.
disconnect();
// Stop any in progress device scan.
stopScan();
// Start scan and connect to first available device.
connectFirst = true;
startScan();
}
// Handlers for BluetoothGatt and LeScan events.
#Override
public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
super.onConnectionStateChange(gatt, status, newState);
if (newState == BluetoothGatt.STATE_CONNECTED) {
if (status == BluetoothGatt.GATT_SUCCESS) {
// Connected to device, start discovering services.
if (!gatt.discoverServices()) {
// Error starting service discovery.
connectFailure();
}
else {
notifyOnConnected(this);
}
}
else {
// Error connecting to device.
connectFailure();
}
}
else if (newState == BluetoothGatt.STATE_DISCONNECTED) {
// Disconnected, notify callbacks of disconnection.
rx = null;
tx = null;
notifyOnDisconnected(this);
}
}
#Override
public void onServicesDiscovered(BluetoothGatt gatt, int status) {
super.onServicesDiscovered(gatt, status);
// Notify connection failure if service discovery failed.
if (status == BluetoothGatt.GATT_FAILURE) {
connectFailure();
return;
}
// Save reference to each UART characteristic.
tx = gatt.getService(UART_UUID).getCharacteristic(TX_UUID);
rx = gatt.getService(UART_UUID).getCharacteristic(RX_UUID);
// Save reference to each DIS characteristic.
disManuf = gatt.getService(DIS_UUID).getCharacteristic(DIS_MANUF_UUID);
disModel = gatt.getService(DIS_UUID).getCharacteristic(DIS_MODEL_UUID);
disHWRev = gatt.getService(DIS_UUID).getCharacteristic(DIS_HWREV_UUID);
disSWRev = gatt.getService(DIS_UUID).getCharacteristic(DIS_SWREV_UUID);
// Add device information characteristics to the read queue
// These need to be queued because we have to wait for the response to the first
// read request before a second one can be processed (which makes you wonder why they
// implemented this with async logic to begin with???)
readQueue.offer(disManuf);
readQueue.offer(disModel);
readQueue.offer(disHWRev);
readQueue.offer(disSWRev);
// Request a dummy read to get the device information queue going
// gatt.readCharacteristic(disManuf);
// Setup notifications on RX characteristic changes (i.e. data received).
// First call setCharacteristicNotification to enable notification.
if (!gatt.setCharacteristicNotification(rx, true)) {
// Stop if the characteristic notification setup failed.
connectFailure();
return;
}
// Next update the RX characteristic's client descriptor to enable notifications.
BluetoothGattDescriptor desc = rx.getDescriptor(CLIENT_UUID);
if (desc == null) {
// Stop if the RX characteristic has no client descriptor.
connectFailure();
return;
}
desc.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
if (!gatt.writeDescriptor(desc)) {
// Stop if the client descriptor could not be written.
connectFailure();
return;
}
// Notify of connection completion.
notifyOnConnected(this);
}
#Override
public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
super.onCharacteristicChanged(gatt, characteristic);
notifyOnReceive(this, characteristic);
}
#Override
public void onCharacteristicRead (BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicRead(gatt, characteristic, status);
if (status == BluetoothGatt.GATT_SUCCESS) {
//Log.w("DIS", characteristic.getStringValue(0));
// Check if there is anything left in the queue
BluetoothGattCharacteristic nextRequest = readQueue.poll();
if(nextRequest != null){
// Send a read request for the next item in the queue
// gatt.readCharacteristic(nextRequest);
}
else {
// We've reached the end of the queue
disAvailable = true;
// notifyOnDeviceInfoAvailable();
}
}
else {
//Log.w("DIS", "Failed reading characteristic " + characteristic.getUuid().toString());
}
}
#Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
super.onCharacteristicWrite(gatt, characteristic, status);
if (status == BluetoothGatt.GATT_SUCCESS) {
// Log.d(TAG,"Characteristic write successful");
}
writeInProgress = false;
}
#Override
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord) {
// Stop if the device doesn't have the UART service.
if (!parseUUIDs(scanRecord).contains(UART_UUID)) {
//main.writeLine("Parse UUID failed...");
//main.messages.append("Parse UUID failed...");
return;
}
// Connect to first found device if required.
if (connectFirst) {
// Stop scanning for devices.
stopScan();
// Prevent connections to future found devices.
connectFirst = false;
// Connect to device.
gatt = device.connectGatt(context, true, this);
}
}
// Private functions to simplify the notification of all callbacks of a certain event.
private void notifyOnConnected(BluetoothLeUart uart) {
for (Callback cb : callbacks.keySet()) {
if (cb != null) {
cb.onConnected(uart);
}
}
}
private List<UUID> parseUUIDs(final byte[] advertisedData) {
List<UUID> uuids = new ArrayList<UUID>();
int offset = 0;
while (offset < (advertisedData.length - 2)) {
int len = advertisedData[offset++];
if (len == 0)
break;
// main.writeLine(advertisedData.toString());
int type = advertisedData[offset++];
switch (type) {
case 0x02: // Partial list of 16-bit UUIDs
case 0x03: // Complete list of 16-bit UUIDs
//main.writeLine("case 02,03...");
// main.messages.append("case 02,03...");
while (len > 1) {
int uuid16 = advertisedData[offset++];
uuid16 += (advertisedData[offset++] << 8);
len -= 2;
uuids.add(UUID.fromString(String.format("%08x-0000-1000-8000-00805f9b34fb", uuid16)));
}
break;
case 0x06:// Partial list of 128-bit UUIDs
case 0x07:// Complete list of 128-bit UUIDs
// Loop through the advertised 128-bit UUID's.
//main.writeLine("case 06,07...");
// main.messages.append("case 06,07...");
while (len >= 16) {
try {
// Wrap the advertised bits and order them.
ByteBuffer buffer = ByteBuffer.wrap(advertisedData, offset++, 16).order(ByteOrder.LITTLE_ENDIAN);
long mostSignificantBit = buffer.getLong();
long leastSignificantBit = buffer.getLong();
uuids.add(new UUID(leastSignificantBit,
mostSignificantBit));
} catch (IndexOutOfBoundsException e) {
// Defensive programming.
//Log.e(LOG_TAG, e.toString());
continue;
} finally {
// Move the offset to read the next uuid.
offset += 15;
len -= 16;
}
}
break;
default:
//main.writeLine("case default...");
// main.messages.append("case default");
offset += (len - 1);
break;
}
}
return uuids;
}
}
Here is my class from where I send the data
public class SwitchClass extends Activity {
public TextView messages;
public Switch Switch1;
public byte[] switchData = {'U','1','1','1','0','0','2','Z'};
private BluetoothLeUart uart;
public void writeLine(final CharSequence text) {
runOnUiThread(new Runnable() {
#Override
public void run() {
messages.append(text);
messages.append("\n");
//messages.setText("anirudh");
}
});
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.switchlayout);
Switch1 = (Switch) findViewById(R.id.switch1);
uart = new BluetoothLeUart(getApplicationContext());
Switch1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
if (isChecked) {
switchString = new String(switchData);
writeLine(switchString);
// send this array 8 bytes to BLE
sendData(switchString);
}
}
});
public void sendData(String sendVal) {
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.append(sendVal.toCharArray(), 0, 8);
uart.send(stringBuilder.toString());
}

You are creating a service from this activity and you are destroying it onStop
so your service is now been disconnected , so automatically you cant get bluetoothgatt and adapter for it
I suggest you to have child fragment inside you activity so your service will stay alive and you can have as many fragment you want to display the thing !!
Hopes this will help you !!

you can visit https://github.com/captain-miao/bleYan, It's a simple BLE library and example.

I also got exactly the same error like yours. In my case I comment out or deleted the following line under onServiceDiscover method. It works suddenly.It may not be the answer, Hope it will give you some clue to solve.
disManuf = gatt.getService(DIS_UUID).getCharacteristic(DIS_MANUF_UUID);
disModel = gatt.getService(DIS_UUID).getCharacteristic(DIS_MODEL_UUID);
disHWRev = gatt.getService(DIS_UUID).getCharacteristic(DIS_HWREV_UUID);
disSWRev = gatt.getService(DIS_UUID).getCharacteristic(DIS_SWREV_UUID);
readQueue.offer(disManuf);
readQueue.offer(disModel);
readQueue.offer(disHWRev);
readQueue.offer(disSWRev);

You must set to synchronized your BluetoothGatt Object like
public void setBluetoothGatt(BluetoothGatt gatt) {
synchronized (this) {
this.bluetoothGatt = gatt;
}
}
because BluetoothGatt throw DeadObject Exception when you change the Activity

Accessing # of WIFI bars in Android

This is the receiver that I have created. The issue is that it does not give me any new values. I feel like it does not receive anything. How can I make myself receive something, why isn't it working here? I did it the same way for battery level and it worked. Finally, when I figure out how to receive something, how am I to get the WIFI bars ( I think if I make this thing return something then the WIFI bars will make more sense).
final BroadcastReceiver mWifiReceiver = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intent) {
final WifiManager wifi = (WifiManager)context.getSystemService(Context.WIFI_SERVICE);
int state = wifi.getWifiState();
if(state == WifiManager.WIFI_STATE_ENABLED) {
List<ScanResult> results = wifi.getScanResults();
for (ScanResult result : results) {
if(result.BSSID.equals(wifi.getConnectionInfo().getBSSID())) {
int level = WifiManager.calculateSignalLevel(wifi.getConnectionInfo().getRssi(),
result.level);
int difference = level * 100 / result.level;
if(difference >= 100)
signalStrength = 4;
else if(difference >= 75)
signalStrength = 3;
else if(difference >= 50)
signalStrength = 2;
else if(difference >= 25)
signalStrength = 1;
}
}
}
}
};
boolean mRegisteredWifiReceiver = false;
Of course I handled the functions not seen here for registering, unregistering, and calling.
Here is how I did that:
public void onVisibilityChanged(boolean visible) {
super.onVisibilityChanged(visible);
if (visible) {
registerReceiver();
registerWifiReceiver();
// registerBatteryReceiver();
// Update time zone in case it changed while we weren't visible.
mTime.clear(TimeZone.getDefault().getID());
mTime.setToNow();
invalidate();
} else {
unregisterReceiver();
unRegisterWifiReceiver();
//unRegisterBatteryReceiver();
}
}
private void registerWifiReceiver() {
if (mRegisteredWifiReceiver)
return;
mRegisteredWifiReceiver = true;
IntentFilter filter = new IntentFilter(WifiManager.RSSI_CHANGED_ACTION);
WatchFaceService.this.registerReceiver(mWifiReceiver, filter);
}
private void unRegisterWifiReceiver() {
if (!mRegisteredWifiReceiver)
return;
mRegisteredWifiReceiver = false;
WatchFaceService.this.unregisterReceiver(mWifiReceiver);
}