view and viewcontroller

Question

I am a new iphone app developer.I want to know what is the difference between view and viewcontroller.

Answer 1

UIView

The UIView class defines a rectangular area on the screen and the interfaces for managing the content in that area. At runtime, a view object handles the rendering of any content in its area and also handles any interactions with that content. The UIView class itself provides basic behavior for filling its rectangular area with a background color. More sophisticated content can be presented by subclassing UIView and implementing the necessary drawing and event-handling code yourself. The UIKit framework also includes a set of standard subclasses you can use, which range from simple buttons to complex tables. For example, a UILabel object draws a text string and a UIImageView object draws an image.

Because your application interacts with the user primarily through view objects, those objects have a number of responsibilities. Here are just a few:

Drawing and animation A view draws content in its rectangular area using technologies such as UIKit, Core Graphics, and OpenGL ES. Some view properties can be animated to new values. Layout and subview management A view may contain zero or more subviews. Each view defines its own default resizing behavior in relation to its parent view. A view can manually change the size and position of its subviews as needed. Event handling A view is a responder and can handle touch events and other events defined by the UIResponder class. A view can use the addGestureRecognizer: method to install gesture recognizers to handle common gestures.

UIViewController

The UIViewController class provides the fundamental view-management model for iPhone applications. The basic view controller class supports the presentation of an associated view, support for managing modal views, and support for rotating views in response to device orientation changes. Subclasses such as UINavigationController and UITabBarController provide additional behavior for managing complex hierarchies of view controllers and views.

You use each instance of UIViewController to manage a view hierarchy. A typical view hierarchy consists of a root view—a reference to which is available in the view property of this class—and usually one or more subviews presenting the actual content. On iPhone and iPod touch, the root view typically fills the entire screen but on iPad this view may fill only part of the screen. In both cases, the view controller is responsible for managing the entire view hierarchy, including all subviews.

View controllers are tightly bound to the views they manage and take part in the responder chain used to handle events. View controllers are themselves descendants of the UIResponder class and are inserted into the responder chain between the managed root view and its superview, which typically belongs to a different view controller. If the view controller’s view does not handle an event, the view controller itself has the option of handling the event before passing the event along to the superview.

The UIViewController class works with the application’s window to handle device orientation changes. If the view controller supports the new orientation (as determined by the return value of its shouldAutorotateToInterfaceOrientation: method), it animates the transition from the current orientation to the new one. As part of this change, it also applies any resizing rules in effect for the views in its view hierarchy. If you want to make changes to your view hierarchy as part of the orientation change, you can override methods of UIViewController to implement your changes. For information on the methods you need to override, see “Handling View Rotations.”

View controllers are fundamental to the design of most iPhone applications. The sections that follow provide basic information about using the methods and properties of the UIViewController class. For additional information about using view controllers to build and manage your application’s user interface, see View Controller Programming Guide for iOS.