Question

I have the following problem.
I have a class named “A” in which I create a list “List dStruct” .
I modify this object in the “A” class and I want to pass it to an Activity for further use.

Also the “A” class extends AsyncTask.

In this case,how do I pass an object to an Activity?

Here is the Activity Code:

List dStruct; //the object I want to access

btnPlanTrip.setOnClickListener(new OnClickListener() {

     tripReq = new TripRequest(MainActivity.this);
     tripReq.execute(request);
     dStruct=tripReq.dStruct;


     String str= dStruct.get(0).name;

}

Here is the code for the class “A”


public class TripRequest extends AsyncTask {

List dStruct;

 public TripRequest(MainActivity activity) {
    this.activity = activity;
    dStruct=new ArrayList <DirectionsStruct>();
    progressDialog = new ProgressDialog(activity);  

}

protected void onPostExecute(Long result) {

   code for dStruct 

 }

}


Answer 1

I solved this issue using Handlers. In my custom AsyncTask, I pass a Handler from an Activity to the constructor. In the AsyncTask’s onPostExecute, I call Handler.sendMessage and it sends whatever data back to the Activity.

AsyncTask Code (your “A” class)

public class MyAsyncTask extends AsyncTask<RestClient, Void, RestResponse> {
     Handler handler;

    public MyAsyncTask(Handler handler) {
         this.handler = handler;
    }

    @Override
    protected RestResponse doInBackground(RestClient... rc) {
        // Get data from web service or whatever...
    }

    @Override
    protected void onPostExecute(RestResponse response){
        Message msg = Message.obtain();
        msg.obj = response;
        this.handler.sendMessage(msg);
    }
}

Handler declared in Activity

private Handler activityHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            // Do something with msg.obj
    };

Call to AsyncTask from Activity passing in Handler to ctor (do this in your button click event handler)

MyAsyncTask async = new MyAsyncTask(activityHandler);
async.execute(...);