Question

I have an application which have UIScrollView with Paging .. and it has arrays with images .. What I want to do is saving which array has been viewed last time the app was running and when I open the app again it should show the last array has been viewed.

Thanks in advance!

Answer 1

Tie your array saving code to the UIApplicationDidEnterBackgroundNotification notification, and then tie your loading code to the UIApplicationDidBecomeActiveNotification notification.

You can also use the appropriate protocol methods in UIApplicationDelegate.

…rereading the question — are you looking for help on how to save something or how to trigger saving at the right time?

Edit

It looks like you’re already following a tutorial with Ray Wenderlich, but I’ll just make a plug for one that I found incredibly simple when I was starting out: http://cocoadevcentral.com/

In terms of saving things to disk, you’ve got several options, the easiest of which is probably to use the NSUserDefaults as another user noted. It’s a dictionary (key : value) system, so you can store your array/image/pathToTheImage, etc. by a name of your choosing, i.e.

“LastImageViewed” : UIImage <–(object) and then load it back by the same name.

 // MyAppDelegate.m
 - (void)applicationDidEnterBackground:(UIApplication *)application {

      // Save
      [[NSUserDefaults standardUserDefaults] setObject:YOUR_ARRAY_GOES_HERE forKey:@"A_NAME_YOU_CHOOSE"];
      [[NSUserDefaults standardUserDefaults] synchronize];

 }

 ...

 - (void)applicationWillEnterForeground:(UIApplication *)application {

      // Load
      NSArray *firstArrayToOpen = [[NSUserDefaults standardUserDefaults] objectForKey:@"THE_NAME_YOU_CHOSE"];

      // Do your thing...
 }

Here’s the reference for the NSUserDefaults class: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html

and the above mentioned notifications and methods reference:
http://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UIApplicationDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intf/UIApplicationDelegate

Does that help?