Android Broadcast Receiver bluetooth events catching

In order to catch Bluetooth state changes (STATE_OFF, STATE_TURNING_ON, STATE_ON, STATE_TURNING_OFF), do this:

First, add Bluetooth permission to your AndroidManifest file:

<uses-permission android:name="android.permission.BLUETOOTH" />

Create a BroadcastReceiver in your Activity or Service:

    private final BroadcastReceiver mBroadcastReceiver1 = new BroadcastReceiver() {    @Override    public void onReceive(Context context, Intent intent) {        final String action = intent.getAction();        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {            final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);            switch(state) {                case BluetoothAdapter.STATE_OFF:                    ..                    break;                case BluetoothAdapter.STATE_TURNING_OFF:                    ..                    break;                case BluetoothAdapter.STATE_ON:                    ..                    break;                case BluetoothAdapter.STATE_TURNING_ON:                    ..                    break;            }        }    }};

Create an IntentFilter and register it with BroadcastReceiver in your Activity/Service's onCreate() method:

@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    IntentFilter filter1 = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);    registerReceiver(mBroadcastReceiver1, filter1);        ...}

Unregister BroadcastReceiver in your onDestroy() method:

@Overrideprotected void onDestroy() {    super.onDestroy();    unregisterReceiver(mBroadcastReceiver1);}

In order to catch changes of discoverability of device (SCAN_MODE_NONE, SCAN_MODE_CONNECTABLE, SCAN_MODE_CONNECTABLE_DISCOVERABLE), create another BroadcastReceiver and register/unregister to your Activity as I mentioned above. Only difference between those BroadcastReceivers is the first one uses BluetoothAdapter.EXTRA_STATE and the other one uses BluetoothAdapter.EXTRA_SCAN_MODE. Here is the example code for BroadcastReceiver to catch discoverability changes:

Create an IntentFilter and register it in onCreate() method:

IntentFilter filter2 = new IntentFilter();filter2.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);filter2.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);filter2.addAction(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED);registerReceiver(mBroadcastReceiver2, filter2);

Create the BroadcastReciver in Activity/Service to catch discoverability changes:

    private final BroadcastReceiver mBroadcastReceiver2 = new BroadcastReceiver() {    @Override    public void onReceive(Context context, Intent intent) {        final String action = intent.getAction();        if(action.equals(BluetoothAdapter.ACTION_SCAN_MODE_CHANGED)) {            int mode = intent.getIntExtra(BluetoothAdapter.EXTRA_SCAN_MODE, BluetoothAdapter.ERROR);            switch(mode){                case BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE:                    ..                    break;                case BluetoothAdapter.SCAN_MODE_CONNECTABLE:                    ..                    break;                case BluetoothAdapter.SCAN_MODE_NONE:                    ..                    break;            }        }    }};

And lastly unregister BroadcastReciver in onDestroy():

unregisterReceiver(mBroadcastReceiver2);

Note that, you don't need to add any <intent-filter> or <receiver> to your AndroidManifest file, except you need to add Bluetooth permission of course.

If you want to catch (ACTION_ACL_CONNECTED, ACTION_ACL_DISCONNECTED, ACTION_ACL_DISCONNECT_REQUESTED), now you need to add an <intent-filter> to your AndroidManifest file:

<intent-filter>    <action android:name="android.bluetooth.device.action.ACL_CONNECTED" />    <action android:name="android.bluetooth.device.action.ACL_DISCONNECTED" /></intent-filter>

Create filter and register it in onCreate() method:

IntentFilter filter3 = new IntentFilter();filter3.addAction(BluetoothDevice.ACTION_ACL_CONNECTED);filter3.addAction(BluetoothDevice.ACTION_ACL_DISCONNECTED);registerReceiver(mBroadcastReceiver3, filter3);

Then create the BroadcastReceiver in your Activity/Service:

    private final BroadcastReceiver mBroadcastReceiver3 = new BroadcastReceiver() {    @Override    public void onReceive(Context context, Intent intent) {        String action = intent.getAction();        switch (action){            case BluetoothDevice.ACTION_ACL_CONNECTED:                ..                break;            case BluetoothDevice.ACTION_ACL_DISCONNECTED:                ..                break;        }    }};

And lastly, unregister:

unregisterReceiver(mBroadcastReceiver3);

If you want to read more about state constants, this is from the documentation:

public static final String EXTRA_STATE:

Used as an int extra field in ACTION_STATE_CHANGED intents to requestthe current power state. Possible values are: STATE_OFF,STATE_TURNING_ON, STATE_ON, STATE_TURNING_OFF

public static final String EXTRA_SCAN_MODE:

Used as an int extra field in ACTION_SCAN_MODE_CHANGED intents torequest the current scan mode. Possible values are: SCAN_MODE_NONE,SCAN_MODE_CONNECTABLE, SCAN_MODE_CONNECTABLE_DISCOVERABLE

I have been trying to replicate the same but not able to achieve success in this regard.

This is my class file

class BluetoothCheckActivity : AppCompatActivity() {private val bluetoothBroadcastReceiver: BroadcastReceiver = object : BroadcastReceiver() {    override fun onReceive(context: Context?, intent: Intent?) {        val action: String? = intent?.action        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {            val state: Int? =                intent?.getIntExtra(                    BluetoothAdapter.EXTRA_STATE,                    BluetoothAdapter.ERROR                )            when (state) {                BluetoothAdapter.STATE_ON -> tv_bluetoothCheck.text = "Bluetooth is On"                BluetoothAdapter.STATE_TURNING_ON -> tv_bluetoothCheck.text =                    "Bluetooth is Turning ON"                BluetoothAdapter.STATE_OFF -> tv_bluetoothCheck.text =                    "Bluetooth is Off"                BluetoothAdapter.STATE_TURNING_OFF -> tv_bluetoothCheck.text =                    "Bluetooth is Turning Off"            }        }    }}override fun onCreate(savedInstanceState: Bundle?) {    super.onCreate(savedInstanceState)    setContentView(R.layout.activity_bluetooth_check)    val filter = IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED)    try {        registerReceiver(bluetoothBroadcastReceiver, filter)    } catch (e: Exception) {        e.printStackTrace()    }}override fun onDestroy() {    unregisterReceiver(bluetoothBroadcastReceiver)    super.onDestroy()}}