The iPhone SDK helps you craft user interfaces.
the visual classes you'll work with and discuss their roles in the interface design.
You read about controllers that work with these visual classes and discover how the handle tasks like device reorientation.
laying out and customizing interface.
both on IB-created interfaces and Objective-C centered ones.
UIView and UIWindow
Nearly everything that appears on the iPhone's screen is a child of the UIView classes.
Views act like litter canvas that you can draw on with colors,pictures,and buttons.You can
draw them around the screen.You can resize them.You can layer them .
Views provide the basic component of user interfaces.
The iPhone rule goes like this:
one Window,many views. very important
UIWindow is the TV set,and UIViews are the actors on your favorite show. The can move around the Tv set,
The can move around the screen,appear, and disappear,and may change the way they look and behave over time.
UIVWindow normally stays still.
You can create several UIWindow in stances in the same application,but
you can watch just one at a time.
UIViews are user interface building blocks. They provide visual elements
the are shown onscreen and invite user interaction.