how to call class AsyncTask to another class?

Question

I tried to call the "AsyncTask" class from another class called "MainActivity" but "AsyncTask" Class is inside the class called "SiteAdapter". I tried to pass a reference but it not working. How could do that?

Main Activity:

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.i("StackSites", "OnCreate()");
        setContentView(R.layout.activity_main);

        //Call the class AsyncTask
        new GetAddressTask(this).execute(); // <----ERROR - GetAddressTask cannot be resolved to a type
    }
}

AsyncTask inside SitesAdapter class:

public class SitesAdapter extends ArrayAdapter<StackSite> { 
    ...//PROCESS

    public class GetAddressTask extends AsyncTask<String, Void, String> {
        Context mContext;
        public GetAddressTask(Context context) {
            super();
            mContext = context;
        }

        //Pass a reference to MainActivity
        private MainActivity mainActivity; // <--- WARNING - The value of the field SitesAdapter.GetAddressTask.mainActivity is not used            
        public GetAddressTask(MainActivity mainActivity)
        {
            this.mainActivity = mainActivity;
        }                           

        @Override
        protected String doInBackground(String... arg0) {
            ...         
        }

        @Override
        protected void onPostExecute(String result) {           
            ...
        }
    }
}

Batuhan Coşkun · Accepted Answer · 2014-11-21T17:30:30.613

First of all, MainActivity is not a class that you can not define an object from. It extends Activity.

Change your AsyncTask class with it;

public static class GetAddressTask extends AsyncTask<String, Void, String> {
    Context mContext;
    public GetAddressTask(Context context) {
         super();
         mContext = context;
    }                          

    @Override
    protected String doInBackground(String... values) {
        // If you want to use 'values' string in here
        String values = values[0];        
    }

    @Override
    protected void onPostExecute(String result) {           
        ...
    }
}

Then call this with it;

String values = ""; //You can pass any string value to GetAddressTask with that parameter
//Call the class AsyncTask
new SitesAdapter.GetAddressTask(this).execute(values);

See my edit @papo . I just changed `AsyncTask`'s `doInBackground`. — Batuhan Coşkun, Nov 21 '14 at 17:31

score 3 · Answer 2 · answered Nov 21 '14 at 15:40

3

make GetAddressTask static:

public static class GetAddressTask

answered Nov 21 '14 at 15:40

debi

59
3

Thanks for you response. I have a warning in te reference "The value of the field SitesAdapter.GetAddressTask.mainActivity is not used" and a error in in calling the class "GetAddressTask cannot be resolved to a type" – Paul Proaño Nov 21 '14 at 15:50
seems that GetAddressTask is not imported – debi Nov 21 '14 at 15:55
if you don't use MainActivity in your AsyncTask then simply remove this field and a constructor as well. – debi Nov 21 '14 at 15:59

score 2 · Answer 3 · edited Nov 21 '14 at 16:11

2

Try this, this is working for me.

Just create a method in your SitesAdapter class and call it from your MainActivity like this :

new SitesAdapter().start(MainActivity.this);

now in your SitesAdapter class do this :

private Context mContext;
public void start(){
   mContext = context;
   new GetAddressTask().execute();
}

May this help you

edited Nov 21 '14 at 16:11

codeMagic

44,549
13
77
93

answered Nov 21 '14 at 15:56

Rahul Patidar

406
3
12

score 0 · Answer 4 · edited May 23 '17 at 12:24

You could make it static then call it with

SitesAdapter.GetAddressTask myClass = new SitesAdapter.GetAddressTask();
myClass.execute();

But, if you are going to be needing this in multiple activities, then it is probably worth it to take it out of that class and put it in its own file.

If you will need to update your UI from the task, you can see this answer on using an interface with a callback to your calling Activity.

how to call class AsyncTask to another class?

4 Answers4