iOS-UIScreen,UIView,UIWindow和UIViewController的介绍和区别

一、参考
View Programming Guide for iOS

http://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/ViewPG_iPhoneOS/Introduction/Introduction.html

View Controller Programming Guide for iOS

http://developer.apple.com/library/ios/#featuredarticles/ViewControllerPGforiPhoneOS/Introduction/Introduction.html

UIScreen Class Reference

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIScreen_Class/Reference/UIScreen.html

UIView Class Reference

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIView_Class/UIView/UIView.html

UIWindow Class Reference

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIWindow_Class/UIWindowClassReference/UIWindowClassReference.html

UIViewController Class Reference

http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIViewController_Class/Reference/Reference.html

二、区别
1、UIScreen可以获取设备屏幕的大小。

// 整个屏幕的大小 {{0, 0}, {320, 480}}CGRect bounds = [UIScreen mainScreen].bounds;NSLog(@"UIScreen bounds: %@", NSStringFromCGRect(bounds));// 应用程序窗口大小 {{0, 20}, {320, 460}}CGRect applicationFrame = [UIScreen mainScreen].applicationFrame;NSLog(@"UIScreen applicationFrame: %@", NSStringFromCGRect(applicationFrame));

应用程序窗口大小 {{0, 20}, {320, 460}}

2、UIView对象定义了一个屏幕上的一个矩形区域，同时处理该区域的绘制和触屏事件。
可以在这个区域内绘制图形和文字，还可以接收用户的操作。一个UIView的实例可以包含和管理若干个子UIView。

ViewController.m

- (void)viewDidAppear:(BOOL)animated{    [super viewDidAppear:animated];    UIView* myView = [[UIView alloc] initWithFrame:CGRectMake(10, 10, 100, 100)];    myView.backgroundColor=[UIColor redColor];    [self.view addSubview:myView];}

3、UIWindow对象是所有UIView的根，管理和协调的应用程序的显示
UIWindow类是UIView的子类，可以看作是特殊的UIView。一般应用程序只有一个UIWindow对象，即使有多个UIWindow对象，也只有一个UIWindow可以接受到用户的触屏事件。

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    UIWindow *myWindow = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];    myWindow.backgroundColor=[UIColor whiteColor];    [myWindow makeKeyAndVisible];    _window = myWindow;    returnYES;}

4、UIViewController对象负责管理所有UIView的层次结构，并响应设备的方向变化。

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    UIWindow *myWindow = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];    myWindow.backgroundColor=[UIColor whiteColor];    UIViewController *myViewController = [[UIViewController alloc] initWithNibName:nil bundle:nil];    myWindow.rootViewController = myViewController;    [myWindow makeKeyAndVisible];    _window = myWindow;    returnYES;}

三、完整的代码

// ViewController.h#import <UIKit/UIKit.h>@interface ViewController : UIViewController@end// ViewController.m#import "ViewController.h"@implementation ViewController- (void)viewDidAppear:(BOOL)animated {    [super viewDidAppear:animated];    UIView* myView = [[UIView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];    myView.backgroundColor=[UIColor redColor];    [self.view addSubview:myView];}- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {    returnYES;}@end// AppDelegate.h#import <UIKit/UIKit.h>@classViewController;@interface AppDelegate : UIResponder <UIApplicationDelegate>@property (strong, nonatomic) UIWindow *window;@property (strong, nonatomic) ViewController *viewController;@end// AppDelegate.m#import "AppDelegate.h"#import "ViewController.h"@implementation AppDelegate@synthesize window = _window;@synthesize viewController = _viewController;- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];    self.viewController = [[ViewController alloc] initWithNibName:nil bundle:nil];     self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];    returnYES;}@end// main.m#import <UIKit/UIKit.h>#import "AppDelegate.h"intmain(intargc, char*argv[]) {    @autoreleasepool {        returnUIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));    }}