Question

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    BluetoothManager btManager = new BluetoothManager(this);
    setContentView(R.layout.main);

    if (!btManager.isEnabled()) {
        btManager.requestBluetoothEnable();
        discoveryStarted = false;

    } else {
        if (btManager.isDeviceSetNullOrEmpty()) {
            btManager.startDiscovery();
            discoveryStarted = true;
        }

    }

}

@Override
public void onResume(){
    super.onResume();

    if( btManager.isEnabled() && discoveryStarted == false ){

I get a NullPointer exception here even though I initialized my btManager class ( a wrapper around a few Bluetooth classes .

Answer 1

BluetoothManager btManager = new BluetoothManager(this);

is only declared locally in the onCreate.

Try putting BlueToothManager btManager; as a class-wide field (just below class declaration). Then, inside oncreate:

btManager = new BluetoothManager(this); 

Then, see if you can access it without the nullpointer inside onResume!