Show Activity when screen is locked (with keyguard - pattern, password, etc...)

Question

I'm developing an application which working on backround and in some particular event I have to show the activity even if the screen is locked.

So I tried to use flags instead of keyguard and wakelock, but I noticed that is only works when the screen is off without any password, pattern and etc... and when there is a password or something else, I see that the screen is turn on but the activity is dismissed...

Note: The activity theme is transparent because I only need to show the speech recognizer dialog...

This is the code I have to show the activity over the keyguard or when the screen is turned off

@Override
public void onAttachedToWindow()
{
    Log.d(TAG, "onAttachedToWindow");
    super.onAttachedToWindow();

    Window window = getWindow();
    window.addFlags
            (
                WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD |
                WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED |
                WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
            );
}

So how can I dismiss the lock screen and show the activity?