Save Current State

By default, when you exit and then re-enter a LiveCode created mobile app no state is saved and your application does not resume from where it left off.

This lesson will explain how to create a simple app, save the state of an app to a text file when the app closes and when re-opened, have this state re-applied.

Create a Stack with Two Cards

Create a new stack with two cards. Card one named "one" and Card two names "two". I have set the size of this stack to 320 x 480

Create some navigation buttons so you can go to and from each card (go next card, go previous card)

Now, create some graphics on each card so that when you navigate, you can tell you are on a new card

Create a file that saves the state on shutdown

We will want to create/add to this file when a shutDown request is triggered. This is possible is we use the shutDown message

The following is added to the stack script-

on shutdown
--set default folder to writeable directory on mobile
set the defaultFolder to specialFolderPath("Documents")
--puts the name of the current card into a text file called mobiletest.txt
put the short name of this card into URL ("file:mobiletest.txt")
pass shutdown
end shutdown

Load this state from the text file

Now that we have saved the state, we will want to load it when the stack is opened. We can do this with the openStack message-

Again, on the stack script, add the following

on openStack
--set default folder to folder with text file in it
set the defaultFolder to specialFolderPath("Documents")
-- places the contents of this text file into a temp variable
put URL ("file:mobiletest.txt") into tState
--navigates to the card names in the temp variable
go card tState
end openStack

Deploy to device/sim

Now when you deploy to a device/sim, exit the app and then re-open the last card that you navigated to will be the one show.

Although this is a very basic example, the same principles can be applied to content within an application as well (e.g. text fields, button states, control positions etc)

Heather Laine

About the Author

Neil is Lead Technical Support Officer for LiveCode