How to modify instance variable from separate AsyncTask

Question

let's say i have an activity with instance variable loadedMovie and a method that executes AsyncTask which is in another file

class MainActivity:AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {

 var loadedMovie: Movie? = null

 ....

 fun loadMovie() {
   val task = LoadMovieTask(this)

   task.execute()
 }
}

separate AsyncTask

class LoadMovieTask(val ctx: Activity) : AsyncTask<Void, Void, Void>() {

  var movie: Movie? = null

  override fun onPreExecute() {
    ....
  }

  // loading information from network
  override fun doInBackground(vararg params: Void?): Void? {
    movie = load()

    return null
  }

  // here i modify views with help of kotlin android extensions
  override fun onPostExecute(result: Void?) {
    ....
  }
}

problem is: somehow i can't modify loadedMovie neither from doInBackground (which is ok, because it runs on separate thread) and onPostExecute (which is not ok)

i just type ctx.loadedMovie in onPostExecute and it's not there.. maybe i don't understand something? or maybe there is another way to do it that i'm not aware of

https://stackoverflow.com/questions/12575068/how-to-get-the-result-of-onpostexecute-to-main-activity-because-asynctask-is-a — Raghunandan, Jun 08 '17 at 06:38
You should use weak reference to hold the activity in async task or else memory leak might happen. — Akshay Bhat 'AB', Jun 08 '17 at 06:43
weak references are well documented for the JVM and Java and all of that documentation applies to Kotlin. This isn't your main problem though as asked. — Jayson Minard, Jun 08 '17 at 11:50

Arun Shankar · Accepted Answer · 2017-06-08T23:17:25.717

0

Use this

class LoadMovieTask(val ctx: MainActivity)

instead of

class LoadMovieTask(val ctx: Activity)

MainActivity has the method and not the Android's Activity class itself. So even though you need the context, since you are trying to access the method specific to MainActivity, it is required to pass that

edited Jun 08 '17 at 23:17

answered Jun 08 '17 at 06:40

Arun Shankar

2,295
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20

It would help the author and future readers of the question if you were to explain why this change is needed. – Jayson Minard Jun 08 '17 at 11:50
@JaysonMinard Thanks for the input, have modified the answer with the reason – Arun Shankar Jun 08 '17 at 23:17

How to modify instance variable from separate AsyncTask

1 Answers1