How can I put graphics items in different layers so that items can be viewed selectively by
simply enabling/disabling the layers. Also how some layers can be drawn frequently and some
drawn infrequently and some drawn only once i.e. selective layer draw.

Example:
1.Background map is static information thus has to be drawn only once.

2.Target information coming from LAN is dynamic and gets updated frequently and different types of targets have to be drawn in different layers so that the operator can view one type of targets using layer selection.

I am using Graphics View Framework of Qt 4.7.