How to let Async Task finish in Android

Question

I'm working on an app that retrieves data from network, stores them to the device and then reads them. Problem is, I get my data in a Async Task.. And my app doesn't let the task finish before trying to show the data to the user.. I've tried task.get() but without result (it just stops there).

Here is my task:

public GetOptionsTask(XMLPortalGetOptions request) {
        super(request);
    }
    protected void onCancelled(){
        // TODO afficher message pas d'options sur le disque
    }
    @Override
    public void handleError(Transaction transaction) {
        // TODO afficher message pas d'options sur le disque
    }
    @Override
    public void handleSuccess(Transaction transaction) {
        saveOptions(transaction.getResponse());
        request = null;
        Log.d(OptionsManager.class.getName(), this.getStatus().toString());
    }

This task is an instance of my custom Async Task:

protected BaseXMLTransaction request;

public abstract void handleError(Transaction transaction);
public abstract void handleSuccess(Transaction transaction);
public TransactionTask(BaseXMLTransaction request){
    this.request = request;
}
@Override
protected Void doInBackground(Void... params) {
    try {
        Log.i(TransactionTask.class.getName(), "Doing in background");
        SocketHandler.sendTransaction(this, request.getRequest());
    } catch (SocketHandlerNotConfiguredException e) {
        Log.e(TransactionTask.class.getName(), "SocketHandler's parameters were not set.");
    }
    return null;
}
@Override
public void transactionResult(Transaction transaction) {
    switch (transaction.getCode()) {
        case ERROR:
            Log.e(TransactionTask.class.getName(), "ERROR !!!");
            handleError(transaction);
            break;
        case NO_CLIENT:
            Log.e(TransactionTask.class.getName(), "No Client Error");
            handleError(transaction);
            break;
        case NO_SERVER:
            Log.e(TransactionTask.class.getName(), "No Server Error");
            handleError(transaction);
            break;
        case OLD_VERSION:
            Log.e(TransactionTask.class.getName(), "Old Version");
            handleError(transaction);
            break;
        case TIMEOUT:
            Log.e(TransactionTask.class.getName(), "Transaction Timeout");
            handleError(transaction);
            break;
        case SUCCESS:
            Log.i(TransactionTask.class.getName(), "Transaction Success");
            handleSuccess(transaction);
    }
}

I seriously don't know what to do... Execute goes to fast and get doesn't do anything since I'm not returning anything I guess.

Answer 1

One thing with that task was that it was saving stuff into a singleton. I managed to call the methods using the information from the network saved in the singleton at the onResume(). When the threads end, it goes to the onResume and everything works fine!

Answer 2

I use an interface as a delegate to do this. Here is an example:

In my main activity I have a onClick listener to trigger my async call and a listener to process once the call is complete.

private void enableLocationButton(){
    locationButton = (Button) findViewById(R.id.locationButton);
    locationButton.setEnabled(true);
    locationButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(MainActivity.this, selectLocationActivity.class);
            intent.putExtra("serverURL",server.getWebServerAddressField());
            startActivityForResult(intent, 200);
        }
    });

}

 @Override
protected void onActivityResult(int requestCode,int resultCode, Intent data){
    if(resultCode == RESULT_OK) {
        switch (requestCode){
            case 100:
                processServerResponse((PmsWebServer) data.getBundleExtra("server").get("server"));
                break;
            case 200:
                processLocationResponse((PmsDataSource)data.getBundleExtra("location").get("location"));
            default:processError();
        }
    }else{
        processError();
    }
}

Somewhere in the selectLocationActivity I have a call to the Async call and something to process the response, please note that this class implements an interface that is used in the Async call.

public class selectLocationActivity extends ListActivity implements SoapServiceInterface{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_location_select);
    chosenServer = this.removeURLHeader(getIntent().getStringExtra("serverURL"));
    this.retrieveLocationOptionsByServer(chosenServer);
}

private void retrieveLocationOptionsByServer(String server) {
    Map<String,Object> parms = new HashMap<String,Object>();
    parms.put(WEB_SERVER_NAME,server);
    SoapServiceObject service = new SoapServiceObject(Services.SERVICE_DETAILS,parms);
    callTheService(service);
}

private void callTheService(SoapServiceObject service){
    SoapServiceHelper helper = new SoapServiceHelper();
    helper.delegate = thisActivity;
    helper.execute(service);
}

@Override
public void serviceCallComplete(SoapObject response){
    this.createClickableListOnScreen(response);
} 
//...more code...//
}

serviceCallComplete is kicked off by the asyncTask. Below is the code for that task

public class SoapServiceHelper extends AsyncTask<SoapServiceObject, Void, SoapObject>{
public SoapServiceInterface delegate = null;
private Integer RETRY_COUNT = 0;
private final Integer MAX_RETRY_COUNT = 2;

protected SoapObject doInBackground(SoapServiceObject... args){
    SoapServiceObject service = args[0];
    try{
        service.callTheService();
    }catch(Exception e){
        System.out.println("An error occurred calling the service\n" + e.getMessage());
    }
    return service.getResponse();
    //return callDateTimeService();
}

protected void onPostExecute(SoapObject result){
    delegate.serviceCallComplete((SoapObject)(result.getProperty(0)));
} 
}

And finally here is the interface

public interface SoapServiceInterface {

    public void serviceCallComplete(SoapObject response);
}

I know I'm displaying something to the screen directly from my result, just sub that part with a save and read ;)

Answer 3

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

and call it like this:

new DownloadFilesTask().execute(url1, url2, url3);

Answer 4

onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.

@Override
protected void onPostExecute(String result) {

}