Reload application data when the app comes into foreground?

Question

I\'m new to iPhone development. I\'m building an app that loads data from a local sqlite3 DB in

-   (BOOL)application:(UIApplication *)application didFinishLaunch         


        

Answer 1

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;