How to detect if bluetooth device is connected

In android how can my Activity will get to know if a Bluetooth A2DP device is connecte开发者_JAVA技巧d to my device.

Is there any broadcast receiver for that?

How to write this broadcast receiver?

Starting from API 11 (Android 3.0) you can use BluetoothAdapter to discover devices connected to a specific bluetooth profile. I used the code below to discover a device by its name:

BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() {
        public void onServiceConnected(int profile, BluetoothProfile proxy) {
            if (profile == BluetoothProfile.A2DP) {
                boolean deviceConnected = false;
                BluetoothA2dp btA2dp = (BluetoothA2dp) proxy;
                List<BluetoothDevice> a2dpConnectedDevices = btA2dp.getConnectedDevices();
                if (a2dpConnectedDevices.size() != 0) {
                    for (BluetoothDevice device : a2dpConnectedDevices) {
                        if (device.getName().contains("DEVICE_NAME")) {
                            deviceConnected = true;
                        }
                    }
                }
                if (!deviceConnected) {
                    Toast.makeText(getActivity(), "DEVICE NOT CONNECTED", Toast.LENGTH_SHORT).show();
                }
                mBluetoothAdapter.closeProfileProxy(BluetoothProfile.A2DP, btA2dp);
            }
        }

        public void onServiceDisconnected(int profile) {
            // TODO
        }
    };
mBluetoothAdapter.getProfileProxy(context, mProfileListener, BluetoothProfile.A2DP);

You can do that for every bluetooth profile. Take a look at Working with profiles in Android's guide.

However, as written in other answers, you can register a BroadcastReceiver to listen to connection events (like when you're working on android < 3.0).

You cannot get the list of connected devices by calling any API. You need instead to listen to the intents ACTION_ACL_CONNECTED, ACTION_ACL_DISCONNECTED that notifies about devices being connected or disconnected. No way to get the initial list of connected devices.

I had this problem in my app and the way I handle it (didn't find better...) is to bounce off/on the Bluetooth at application start to be sure to start with an empty list of connected devices, and then listen to the above intents.

muslidrikk's answer is broadly correct; however you can alternatively use fetchUUIDsWithSDP() and see what you get back... it's a bit of a hack though -- you'd have to know what UUIDs (capabilities) you could expect from the device, if it were turned on. And that might be difficult to guarantee.

For BluetoothHeadset specifically, you can call getConnectedDevices() to get connected devices for this specific profile.

Reference: http://developer.android.com/reference/android/bluetooth/BluetoothHeadset.html

Other cases you need to register a receiver for that.

In your activity, define broadcast receiver...

// Create a BroadcastReceiver for ACTION_FOUND
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
    String action = intent.getAction();
    // When discovery finds a device
    if (BluetoothDevice.ACTION_FOUND.equals(action)) {
        // Get the BluetoothDevice object from the Intent
        BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
        // Add the name and address to an array adapter to show in a ListView
        mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
    }
}

};

 // Register the BroadcastReceiver

IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestroy