How to detect Bluetooth state change using a broadcast receiver?

Question

I am trying to make an app that shows a toast when the device's Bluetooth turned on. I wanna do that even when my app is not running. So I should use a broadcast receiver, add some permissions, an intent-filter to android manifest and make a java class but I don't know the details.

What should I do? Which permissions should I use?

Answer 1

AS far as permissions go, to detect the state change of bluetooth you need to add this to your AndroidManifest.xml.

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

An example receiver would look like this, you add this code to where you want to handle the broadcast, for example an activity:

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {             public void onReceive (Context context, Intent intent) {                 String action = intent.getAction();                  if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {                     if(intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1)      == BluetoothAdapter.STATE_OFF)     // Bluetooth is disconnected, do handling here }  }          }; 

To use the receiver, you need to register it. Which you can do as follows. I register the receiver in my main activity.

registerReceiver(this, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED)); 

You could also decide to add all of it to your AndroidManifest.xml. This way you can make a special class for the receiver and handle it there. No need to register the receiver, just make the class and add the below code to the AndroidManifest

<receiver         android:name=".packagename.NameOfBroadcastReceiverClass"         android:enabled="true">     <intent-filter>         <action android:name="android.bluetooth.adapter.action.STATE_CHANGED"/>     </intent-filter> </receiver>