what do you mean locking the notification bar? you mean not receiving any notification for the moment?
regarding your question. What you can do is make your Toolbar not clickable or more specifically make the Navigation Drawer not clickable so the user can not open it.
EDIT:
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
you can do this:
WindowManager manager = ((WindowManager) getApplicationContext()
.getSystemService(Context.WINDOW_SERVICE));
WindowManager.LayoutParams localLayoutParams = new WindowManager.LayoutParams();
localLayoutParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ERROR;
localLayoutParams.gravity = Gravity.TOP;
localLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE|
// this is to enable the notification to recieve touch events
WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |
// Draws over status bar
WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
localLayoutParams.width = WindowManager.LayoutParams.MATCH_PARENT;
localLayoutParams.height = (int) (50 * getResources()
.getDisplayMetrics().scaledDensity);
localLayoutParams.format = PixelFormat.TRANSPARENT;
customViewGroup view = new customViewGroup(this);
manager.addView(view, localLayoutParams);
or look at this posted question: Disable the notification panel from being pulled down