按住Home后，退出保存数据

ApplicationWillExit.m

- (void)applicationWillResignActive:(UIApplication *)application {
    /*
     Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
     Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
     */
	
	NSLog(@"applicationWillResignActive");
	
	UIApplication *app = [UIApplication sharedApplication];    
    BOOL backgroundSupported = NO;
	
	// 判断是否支持多任务
	UIDevice* device = [UIDevice currentDevice];
    if ([device respondsToSelector:@selector(isMultitaskingSupported)]) {
		backgroundSupported = device.multitaskingSupported;
	}

    if(backgroundSupported==NO) { // 不支持多任务
        [[NSNotificationCenter defaultCenter ] addObserver:self
                                                  selector:@selector(applicationWillTerminate:)
                                                      name:UIApplicationWillTerminateNotification
                                                    object:app];
    } else {   // 表示支持多任务     
        /*这个新的UIApplicationWillResignActiveNotification就是在用户按下home键时的通知，
		  建议用它的selector去保存数据，能防止用户直接在任务管理器里强制退出～*/
        [[NSNotificationCenter defaultCenter ] addObserver:self
                                                  selector:@selector(applicationDidEnterBackground:)
                                                      name:UIApplicationWillResignActiveNotification
                                                    object:app];
        
		/*这个UIApplicationWillEnterForegroundNotification是app在切回前台时的通知，可以显示“欢迎回来”之类的*/
        [[NSNotificationCenter defaultCenter ] addObserver:self
                                                  selector:@selector(applicationDidBecomeActive:)
                                                      name:UIApplicationWillEnterForegroundNotification
                                                    object:app];
        
    }
	
	
}


- (void)applicationDidBecomeActive:(UIApplication *)application {
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive.
     */
	NSLog(@"applicationDidBecomeActive");
}


- (void)applicationDidEnterBackground:(UIApplication *)application {
	/*
     Called when the application entered background.
     */
	NSLog(@"applicationDidEnterBackground");
	
	// save local data here when suppourt mutitasks
	
}

- (void)applicationWillTerminate:(UIApplication *)application {
    /*
     Called when the application is about to terminate.
     */
	NSLog(@"applicationWillTerminate");
	
	// save local data here when not suppourt mutitasks
}