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?

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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).

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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.

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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.

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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.

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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