int currentNightMode = getContext().getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;  
switch (currentNightMode) {
    case Configuration.UI_MODE_NIGHT_NO:
        // Night mode is not active, we're using the light theme
        break;
    case Configuration.UI_MODE_NIGHT_YES:
        // Night mode is active, we're using dark theme
        break;
}