Android Question Storing Activity State in External Class

DawningTruth · Mar 23, 2019

I need to create an external class for storing activity data during the activity lifecycle.

Here is the envisioned Sequence:

The Activity is quite complex. Having sophisticated custom elements.

So I need to be able to carry the state across from activity destruction to activity recreation. I understand that UI elements cannot be serialised so it is not possible to save the activities in a datastore. So, I will have to save them in a persistent class.

Now to the question. How is this done?

I have tried declaring the class in my Main Activity, and then using it in the above activity (Working Activity), but it keeps giving me an error. If I declare the class in the Working Activity, then it is destroyed when the activity is destroyed during the pause event.

By declared I am using code like:

B4X:

'In Working Activity
Private StorageClass1 As StorageClass

'When I tried Main Activity Declaration
Public StorageClass1 As StorageClass

Any suggestions?

agraham · Mar 23, 2019

Anything declared in Process_Globals should survive while the app process exists. You can't put Activity objects there but you can save state such as Strings and Ints etc.

MarkusR · Mar 23, 2019

there is something ready that save/load the ui state
i believe it was this StateManager
https://www.b4x.com/android/forum/t...applications-settings-and-state.9777/#content

its also possible that android not destroy the activity.

if you put the declaration in Process_Globals
Public StorageClass1 As StorageClass
and it was initialized
StorageClass1.Initialize once
you can access it via Main.StorageClass1. ...
in StorageClass use a public sub or properties set/get

DawningTruth · Mar 23, 2019

agraham said:
Anything declared in Process_Globals should survive while the app process exists. You can't put Activity objects there but you can save state such as Strings and Ints etc.

Thx Agraham

DawningTruth · Mar 23, 2019

MarkusR said:
there is something ready that save/load the ui state
i believe it was this StateManager
https://www.b4x.com/android/forum/t...applications-settings-and-state.9777/#content

its also possible that android not destroy the activity.

if you put the declaration in Process_Globals
Public StorageClass1 As StorageClass
and it was initialized
StorageClass1.Initialize once
you can access it via Main.StorageClass1. ...
in StorageClass use a public sub or properties set/get

Thx Markus.

I managed to get the second option working

DawningTruth · Mar 23, 2019

Ok, have tried the suggested approach. It is retaining the state of the elements, however when I try to recreate the view in Landscape, none of the elements are transferring across.

So for instance I have a label value. I copy the lbl_MyLabel UI element to Main.StorageClass1.MyLabel at pause. However when I copy the value back into lbl_MyLabel during the resume process. Nothing is copied back into the label value.

Any suggestions?

Erel · Mar 24, 2019

DawningTruth said:
It is retaining the state of the elements, however when I try to recreate the view in Landscape, none of the elements are transferring across.

I'm not sure what you mean here however you cannot reuse the same views after the activity was destroyed.

Check the suggested state manager module. It saves the user related state and sets it again when the activity is created.

DawningTruth · Mar 24, 2019

Erel said:
I'm not sure what you mean here however you cannot reuse the same views after the activity was destroyed.

Check the suggested state manager module. It saves the user related state and sets it again when the activity is created.

Thx Erel, I will look at it. Does it support all the B4A views?

Erel · Mar 24, 2019

The question is not accurate enough for me to give a full answer. It only saves user related state. It supports all native views. In some cases you will need to do some work to get the state of all views (see the code, it is quite simple).

DawningTruth · Mar 25, 2019

Erel said:
The question is not accurate enough for me to give a full answer. It only saves user related state. It supports all native views. In some cases you will need to do some work to get the state of all views (see the code, it is quite simple).

Thx Erel, I will investigate further...

MarkusR · Mar 25, 2019

It is retaining the state of the elements, however when I try to recreate the view in Landscape, none of the elements are transferring across.

if android not recreate the activity / ui then u need handle the new orientation by yourself.

DawningTruth · Mar 25, 2019

MarkusR said:
if android not recreate the activity / ui then u need handle the new orientation by yourself.

Thx Markus, it appears like that is the root I will have to take as the required UI Elements are not supported.

Android Question Storing Activity State in External Class

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