Unable to get data from from inner class

Question

I have a Inner class which extends AsyncTask inside my main class

public class MainActivity extends Activity {
String variable;
public onCreate(){

    onClickListener{
    new InnerClass().execute(params);
    variable // Here the value is always null
    }
}

class InnerClass extends AsyncTask<String,Void,JSONObject>{
    protected JSONObject doInBackground(String... params){
        /* Relevant Code 
        */
    }

    protected void onPostExecute(JSONObject result){
    variable = value; // required value being assigned to the variable
    }

}
}

I am getting proper value assigned to the my String Variable "variable" in the inner class, but i am not able to the access the value in my main class.

You shouldn't expose around public variables like that. Instead use a callback and use that in the inner class to trigger a method in the main class — Tim, Sep 22 '15 at 09:26
That's because you're looking at the value before the async task has set it... — user253751, Sep 22 '15 at 09:26

David Herrero · Accepted Answer · 2015-09-22T09:27:09.010

2

new InnerClass().execute(params);
variable // Here the value is always null

You call execute but your main thread continue, so variable is still null because AsyncTask.onPostExecute was still not called.

edited Sep 22 '15 at 09:27

answered Sep 22 '15 at 09:23

David Herrero

704
5
17

1

That is not the issue. the issue is that the variable is accessed in main before it is set in the inner class – Tim Sep 22 '15 at 09:25
I answered with the original question, withput editing, so maybe i didnt undestand you. Sorry. – David Herrero Sep 22 '15 at 09:28
The issue in the original question was the same. I only slightly edited the question title (and changed it back afterwards) – Tim Sep 22 '15 at 09:28
Yap,i know, i edited my answer as soon as i could – David Herrero Sep 22 '15 at 09:32

score 0 · Answer 2 · answered Sep 22 '15 at 09:26

0

You use async task, it creates thread for you to execute your code. Your variable is null because your thread didn't finish his job.

answered Sep 22 '15 at 09:26

Artur Szymański

1,639
1
19
22

score 0 · Answer 3 · answered Sep 22 '15 at 09:46

0

create inner class object like.

InnerClass inner=new InnerClass();
String name=inner.name;

That's it.

answered Sep 22 '15 at 09:46

Ganpat Kaliya

888
2
9
16

score 0 · Answer 4 · answered Sep 22 '15 at 11:52

If you wan result from your asynk task you can do like that: Separate class for asynk task:

class InnerClass extends AsyncTask<String,Void,JSONObject>{
  protected JSONObject doInBackground(String... params){
    /* Relevant Code 
    */
  }
}

In your activity:

public class MainActivity extends Activity {
  String variable;
  public onCreate(){

     onClickListener{
      startAsync();
     }
   }
  private void startAsync(){
         InnerClass task = new InnerClass(){

          protected void onPostExecute(JSONObject result){
              variable = value;
          }

         };
         task.execute(params);

  }
 }

This is only for adaptation of your code. Better way is to make long tasks in appliaction context ,and sending results to activities/ fragments by EventBus. If you use above implementaion you have to create methods to canceling task when onDestroy is called.

Unable to get data from from inner class

4 Answers4