Reload application data when the app comes into foreground?

So in the App Delegate class - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions will only be called at the first time you enter the app.Then it will call - (void)applicationDidBecomeActive:(UIApplication *)application.

If your iphone iOS is 4.0 or later, when a user click on the home button, it will first invoke - (void)applicationWillResignActive:(UIApplication *)application, then - (void)applicationDidEnterBackground:(UIApplication *)application.

Then the app will run in background till the user kill it. When the user enter the app again, it will first invoke - (void)applicationWillEnterForeground:(UIApplication *)application, then - (void)applicationDidBecomeActive:(UIApplication *)application.

So related to your question, you should call either applicationWillEnterForeground: or applicationDidBecomeActive: to reload your data. Though in the xcode's comment of these methods, Apple suggests use applicationDidBecomeActive: to restart paused tasks and/or update user interface; while in the applicationWillEnterForeground:, you can undo the changes you've made in entering the background.

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So to make it easier to see, i put a number tag to each method. Here's when the method to be called.

0 application:(UIApplication *)application didFinishLaunchingWithOptions: 
1 applicationDidBecomeActive: 
2 applicationWillResignActive: 
3 applicationDidEnterBackground: 
4 applicationWillEnterForeground: 

• First enter the app: call 0, then 1;

• Hit home button: call 2, then 3;

• Double hit home button(multitasking): call 2;

  • if user choose another app or hit home button again: call 3;

  • if user double hit home button again: call 1;

• Enter app again: call 4, then 1;

- (void)applicationDidBecomeActive:(UIApplication *)application {
}

Reload the data in the above function of the app delegate to refresh the data when ever the app comes to foreground.

You can exit() your application when iOS notifies it that it should run in the background like so:

- (void)applicationDidEnterBackground:(UIApplication *)application {
  exit(0);
}