iOS-- Managing Subviews

1. Adding Subviews

•  insertSubview:atIndex:
•  insertSubview:aboveSubview:
•  insertSubview:belowSubview:

2. Reordering and Removing Subviews

• Use [parentView exchangeSubviewAtIndex:i withSubviewAtIndex:j] to exchange the positions of two views.
• Move subviews to the front or back using bringSubviewToFront: and 
• sendSubviewToBack.
• To remove a subview from its parent, call [childView removeFromSuperview]. If 
• the child view had been onscreen, it disappears. Removing a child from the superview 
• calls a release on the subview, allowing its memory to be freed if its retain
• count has returned to 0.

3. View Callback

•  didAddSubview: is sent to a view after a successful invocation of addSubview: lets subclasses of UIView perform additional actions when new views are added.
• didMoveToSuperview: informs views that they’ve been re-parented to a new superview. The view may want to respond to that new parent in some way.When the view was removed from its superview, the new parent is nil.
• willMoveToSuperview: is sent before the move occurs.
• didMoveToWindow: provides the callback equivalent of didMoveToSuperview but when the view moves to a new Window hierarchy instead of to just a new superview.
• willMoveToWindow: is, again, sent before the move occurs.
• willRemoveSubview: informs the parent view that the child view is about to be removed.