CODEWITHSUNDEEP
androidgarbage-collection
zzy
zzy

Reputation: 1793

How does android do GC?

Now I'm facing some problem in Android when memory is low or the application is killed by system.

Scenario 1:

I set some static members in a class, I found in some situation , it will be deleted by system when the application is still running.

My problem to this is : when does this kind of GC run?

Scenario 2:

If I switch to another large application and then switch back to my application ( named App_A). App_A sometimes will be recycled by system and restart the last activity when it be switched back.

But there are some application-wide data (like login info) I saved in a singleton.

My problem to this is : Dose the application-wide data saved in singleton will be deleted? If so, is there a appropriate way to restore the data?

My effort is:

  1. To Scenario 1, I will avoid to use static member directly.
  2. To Scenario 2, I will save those data into file , after it be deleted, I pass Context to each public function to let each of them have the ability to restore the data. But I think it will be unfriendly when the function is used in some situation which need run quickly.

Upvotes: 0

Views: 77

Answers (2)

kris larson
kris larson

Reputation: 30985

I can only answer about Scenario 2.

Android will try to keep recently used apps in memory, but if the user switches to another app and memory starts running low, the OS has the option to kill the recently used app to make more memory available to running applications.

I had the same problem, where I had some user-context data like username in a static singleton. This data would disappear when returning to the app after using a number of other apps.

The way I solved this problem was to use the activity's intent. Since the user data was retrieved at the beginning of the app, I would simply pass this data to subsequent activities in their intents. Because the OS stores the intent and uses it to recreate an activity not in memory, my data was no longer vulnerable to being garbage-collected.

Also consider other means of persisting data: Shared Preferences, file system, SQLite database. But never count on static data from previous execution being available at the start of an activity.

Upvotes: 1

Валентин Тараненко
Валентин Тараненко

Reputation: 126

It is generally bad idea to use singleton to save some data.
Best practice is using any persistent storage - SQLite, Realm,JSON, or any file.
Easiest way is saving your login data for ex. in JSON - then in Application class parse it in onCreate method into POJO - then you can get it from any place of your app. And store to file when app is closing or on any change. Anyway I suggest you to read Android guides about persistence, memory management and performance tips.

Upvotes: 0

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