How to stop view updates when app is in background (or sleeping)?

Question

The Executing Code in the Background asks for "Avoid updating your windows and views".

Because the UI updates are all over different views in various methods, what I can think of is setting a BOOL 'global' within each view controller (e.g. under the @implementation mapViewController), and use many if (BOOL) controls to stop updating IBOutlets such as textView, UILabel, map annotations etc. in relevant methods.

But I feel this is not a good way of doing it.

I wonder how you guys do to "Avoid updating your windows and views"?