iOS 运行程序和进入后台通知

1.创建俩个NSNotificationCenter的 通知

a).
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:)
name:UIApplicationWillResignActiveNotification object:nil]; //监听是否触发home键挂起程序，（把程序放在后台执行其他操作）
b).
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationDidBecomeActive:)
name:UIApplicationDidBecomeActiveNotification object:nil]; //监听是否重新进入程序程序.（回到程序)

2.实现俩个NSNotificationCenter触发的函数

• (void)applicationWillResignActive:(NSNotification *)notification
  {
  nslog(“触发home按下”);
  }

• (void)applicationDidBecomeActive:(NSNotification *)notification
  {
  nslog(“重新进来后响应”);
  }

在home键触发后，程序进入后台，app delegate响应的函数为：

• (void)applicationDidEnterBackground:(UIApplication *)application
  {

  }