Passiondroid Passiondroid - 1 month ago 54
Android Question

How to programmatically pair and connect a HID bluetooth device(Bluetooth Keyboard) on Android

I am able to pair a bluetooth keyboard but not able to connect so as to make it an input device.
I went through the documentation provided at developer site - http://developer.android.com/guide/topics/connectivity/bluetooth.html#Profiles

It says that the Android Bluetooth API provides implementations for the following Bluetooth profiles but you can implement the interface BluetoothProfile to write your own classes to support a particular Bluetooth profile.


  • Headset

  • A2DP

  • Health Device



There is no documentation how to implement BluetoothProfile for HID bluetooth device(Keyboard)

Android has itself implemented bluetooth connection for HID devices but those API's are hidden. I tried reflection to use them too. I do not get any error but keyboard does not get connected as input device. This is what i have done -

private void connect(final BluetoothDevice bluetoothDevice) {
if(bluetoothDevice.getBluetoothClass().getDeviceClass() == 1344){
final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothProfile.ServiceListener mProfileListener = new BluetoothProfile.ServiceListener() {
@Override
public void onServiceConnected(int profile, BluetoothProfile proxy) {
Log.i("btclass", profile + "");

if (profile == getInputDeviceHiddenConstant()) {
Class instance = null;
try {
//instance = Class.forName("android.bluetooth.IBluetoothInputDevice");
instance = Class.forName("android.bluetooth.BluetoothInputDevice");
Method connect = instance.getDeclaredMethod("connect", BluetoothDevice.class);
Object value = connect.invoke(proxy, bluetoothDevice);
Log.e("btclass", value.toString());
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}



}
}

@Override
public void onServiceDisconnected(int profile) {

}
};

mBluetoothAdapter.getProfileProxy(this, mProfileListener,getInputDeviceHiddenConstant());


}

}

public static int getInputDeviceHiddenConstant() {
Class<BluetoothProfile> clazz = BluetoothProfile.class;
for (Field f : clazz.getFields()) {
int mod = f.getModifiers();
if (Modifier.isStatic(mod) && Modifier.isPublic(mod) && Modifier.isFinal(mod)) {
try {
if (f.getName().equals("INPUT_DEVICE")) {
return f.getInt(null);
}
} catch (Exception e) {
Log.e("", e.toString(), e);
}
}
}
return -1;
}

Answer

Due to security reasons, it is not possible for third party applications to connect to a bluetooth keyboard as the application can be a keylogger. So it can be only done manually by the user.