建立UIApplicationDelegateDemo主要用来明确应用程序进入前台、按home键进入后台以及在此唤醒进入前台函数的调用顺序。

1 //  2 //  AppDelegate.h  3 //  UIApplicationDelegateDemo  4 //  5 //  Created by Fox on 12-3-14.  6 //  Copyright (c) 2012年 __MyCompanyName__. All rights reserved.  7 //  8  9 #import 
     
       10 11 @class ViewController; 12 13 @interface AppDelegate : UIResponder 
      
       {
   14 15 } 16 17 @property (strong, nonatomic) UIWindow *window; 18 @property (strong, nonatomic) ViewController *viewController; 19 20 @end
      
     

1 //  2 //  AppDelegate.m  3 //  UIApplicationDelegateDemo  4 //  5 //  Created by Fox on 12-3-14.  6 //  Copyright (c) 2012年 __MyCompanyName__. All rights reserved.  7 //  8  9 #import "AppDelegate.h" 10 11 #import "ViewController.h" 12 13 @implementation AppDelegate 14 15 @synthesize window = _window; 16 @synthesize viewController = _viewController; 17 18 - (void)dealloc 19 {
   20     [_window release]; 21     [_viewController release]; 22     [super dealloc]; 23 } 24 /* 25  *当程序完成载入，并且可能有额外的启动选项时被调用,用于程序的初始化 26  */ 27 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 28 {
   29     NSLog(@"Fox:didFinishLaunchingWithOptions"); 30     self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease]; 31     self.viewController = [[ViewController alloc] initWithNibName:@"ViewController" bundle:nil]; 32     self.window.rootViewController = self.viewController; 33     [self.window makeKeyAndVisible]; 34     return YES; 35 } 36 /* 37  *应用程序初始化完成后，程序转为激活状态时被调用 38  */ 39 - (void)applicationDidBecomeActive:(UIApplication *)application 40 {
   41     NSLog(@"Fox:applicationDidBecomeActive"); 42     /* 43      Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface. 44 */ 45 } 46 47 48 /* 49  *应用程序转为后台（非激活）状态时被调用，即按home键后先调用该方法 50  */ 51 - (void)applicationWillResignActive:(UIApplication *)application 52 {
   53     NSLog(@"Fox:applicationWillResignActive"); 54 } 55 56 /* 57  *程序转到后台后，调用此方法，若想在后台运行程序，在此处添加. 58  *应用此方法来释放资源，保存数据，使计时器停止，存储应用程序状态和信息 59  */ 60 - (void)applicationDidEnterBackground:(UIApplication *)application 61 {
   62     NSLog(@"Fox:applicationDidEnterBackground"); 63 } 64 65 66 /* 67  *应用程序将要从后台进入前台时调用带方法 68  */ 69 - (void)applicationWillEnterForeground:(UIApplication *)application 70 {
   71     NSLog(@"Fox:applicationWillEnterForeground"); 72     /* 73      Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background. 74 */ 75 } 76 77 78 /* 79  *应用程序将要终止时调用 80  */ 81 - (void)applicationWillTerminate:(UIApplication *)application 82 {
   83     NSLog(@"Fox:applicationWillTerminate"); 84     /* 85      Called when the application is about to terminate. 86      Save data if appropriate. 87      See also applicationDidEnterBackground:. 88 */ 89 } 90 91 @end

程序运行后，调用的函数如下：

点击home键后：

在此点击程序，程序返回主界面：