iOS AppDelegate方法，监听进程在后台、被杀死事件

- (BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions{

NSLog(@"启动程序，didFinishLaunchingWithOptions");

returnYES;

}

- (void)applicationWillResignActive:(UIApplication*)application

{

NSLog(@"将变为非活跃状态，applicationWillResignActive");

}

- (void)applicationDidEnterBackground:(UIApplication*)application

{

NSLog(@"进入后台，applicationDidEnterBackground");

}

- (void)applicationWillEnterForeground:(UIApplication*)application

{

NSLog(@"由后台进入前台，applicationWillEnterForeground");

}

- (void)applicationDidBecomeActive:(UIApplication*)application

{

NSLog(@"变为活跃状态，applicationDidBecomeActive");

}

- (void)applicationWillTerminate:(UIApplication*)application

{

NSLog(@"程序被杀死，applicationWillTerminate");

}

- (void)application:(UIApplication*)application handleEventsForBackgroundURLSession:(NSString*)identifier completionHandler:(void(^)(void))completionHandler

{

NSLog(@" 应用处于后台，所有下载任务完成调用，handleEventsForBackgroundURLSession");

}

先定义一个后台任务标识：UIBackgroundTaskIdentifier backgroundTaskIdentifier;
 
- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // 若不实现该代码，进入后台，不会响应定时器事件
    backgroundTaskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^(){
        // 程序在进入后台一定时间后，我测试是180秒左右，若还未结束后台任务，则会响应该回调，若已结束，则不会进入该回调
        NSLog(@"beginBackgroundTaskWithExpirationHandler");
    }];
    
    // 这里进行需要的操作，可在操作完成调用endBackgroundTask结束后台任务
    [NSTimer scheduledTimerWithTimeInterval:1.f target:self selector:@selector(timerAction) userInfo:nil repeats:YES];
}
 
- (void)timerAction
{
    static int a = 0;
    if (a == 100) [self endBackgroundTask];
    NSLog(@"a : %d", a++);
}
 
- (void)endBackgroundTask
{
    [[UIApplication sharedApplication] endBackgroundTask:backgroundTaskIdentifier];
    backgroundTaskIdentifier = UIBackgroundTaskInvalid;
}

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    // 实现如下代码，才能使程序处于后台时被杀死，调用applicationWillTerminate:方法
    [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^(){}];
}
 
- (void)applicationWillTerminate:(UIApplication *)application
{
    NSLog(@"程序被杀死，applicationWillTerminate");
}