In PC, most apps use Windows to display content, and mobile apps are no exception. To display content on the screen in mobile apps, you must first create a window to carry content, the iOS app uses UIWindow and UIView to display content.
UIWindow:
The UIWindow object is the root View of all uiviews. It manages and coordinates the display and distribution events of applications to the View. The UIWindow class is a subclass of UIView and can be considered as a special UIView. Generally, an application only has one UIWindow object. Even if multiple UIWindow objects exist, only one UIWindow can receive user touch screen events. UIWindow initializes the didfinishlaunchingwitexceptions method in appDeleDgate.
Self. window = [[[UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds] autorelease]; // Override point for customization after application launch. self. window. backgroundColor = [UIColor whiteColor]; [self. window makeKeyAndVisible]; // displays the UIWindow
UIView:
The UIView class inherits from UIResponder and defines a rectangular area on the screen. The view is used to display the interface and respond to user interface interaction. Each view object is responsible for rendering the content of the view area and responding to Operation events in the area.
In addition to displaying content and processing events, the view can be nested and manage subviews. A subview is a view object embedded in another view object, and the embedded view object is a parent view. The view is displayed when it is added to the window. For how to display the view in iOS, see the following code:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease]; // Override point for customization after application launch. self.window.backgroundColor = [UIColor whiteColor]; CGRect rect=[UIScreen mainScreen].applicationFrame; NSLog(@"NSScreen application %@",NSStringFromCGRect(rect)); CGRect rect2=[UIScreen mainScreen].bounds; NSLog(@"NSString mainScreen %@",NSStringFromCGRect(rect2)); NSLog(@"iOS_didFinishLaunchingWithOptions"); UIView *view1=[[UIView alloc]initWithFrame:CGRectMake(60, 50, 200, 100)]; view1.backgroundColor=[UIColor greenColor]; [self.window addSubview:view1]; [view1 release]; UIView *view2=[[UIView alloc]initWithFrame:CGRectMake(60, 100, 200, 200) ]; view2.alpha=0.5; view2.backgroundColor=[UIColor cyanColor]; [self.window addSubview:view2]; UIView *view3=[[UIView alloc]initWithFrame:CGRectMake(100, 50, 60, 50)]; view3.backgroundColor=[UIColor colorWithRed:25/255.0 green:60/255.0 blue:150/255.0 alpha:1.0]; [view2 addSubview:view3]; [view3 release]; [view2 release]; [self.window makeKeyAndVisible]; return YES;}
Three Views are added above. view1, view2, view3, and view3 are nested in view2.
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