CODEWITHSUNDEEP
androidmultithreadingserviceandroid-activitybackground
Kubus
Kubus

Reputation: 23

Android - Running heavy computations in background and returning the result to an Activity

I have implemented some computationaly heavy functions into my application. Depending on the type of input it can take up to several minutes for a thread to return. During this time, I want the user to be able to work with other activities to perform different tasks (i.e. prepare data for the next run). Then, after the Service has finished it's computations, the user should be notified with a Toast that the result is ready and that he should check back to the Activity he started the Service in. Unfortunately I'm stuck at this point.

Is it possible to somehow communicate with an Activity which is destroyed at the moment? Like modifying the saved state, so that when it get's recreated the result will be displayed. The only way of communication I did find was via broadcasting from the Service, but this requires the Activity to listen, which is not possible as it doesn't exist at the moment the Service finishes.

The only solution that occured to me was writing a file when the Service is finished and then trying to read it in the Activity, but I would prefer not to work with the file system if that's possible.

Am I missing something here or thinking in the wrong direction?

Upvotes: 0

Views: 534

Answers (3)

Booger
Booger

Reputation: 18725

I would use an AsyncTask, and return the value from your computation to some stateful location (use an Application class, or SharedPreferences even).

Have the AsyncTask launch your Activity on completion, and get the value you statefully stored to display.

Basically, combine the 1st 2 answers and you should be set.

Upvotes: 0

Saad Farooq
Saad Farooq

Reputation: 13402

You could just write to a SharedPreference from the Service.

The Activity can check the preference whenever it is started and you can have some marker to indicate that the result was from your computation.

You could also write to the same SharedPreference from the Activity to nullify it so that it can be used for the next result.

Upvotes: 0

Alexander Fuchs
Alexander Fuchs

Reputation: 1358

use Asynctask http://developer.android.com/reference/android/os/AsyncTask.html

Upvotes: 1

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