How can I make the status bar go back up after being pulled down on an android app?

Question

I've added the following code to my onCreate method:

View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);`

but when I then pull down the status bar, it doesn't go away again like I would like it to. I'm assuming that's because it's in the onCreate method, but what can I do to rectify this?